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Item Open Access Breed effects and non additive genetic variation in indigenous and commercial sheep in an extensive environment(University of the Free State, 2019-06) Kao, 'Mamolleloa A.; Van Wyk, J. B.; Cloete, S. W. P.The first part of the study compared a commercial, the Dorper as an arguably adapted commercial breed to the Namaqua Afrikaner as an unselected, indigenous, far-tail breed. The Dorper conclusively outperformed the Namaqua Afrikaner with reference to live weight and growth traits. On the other hand, Namaqua Afrikaner lambs were superior to Dorpers for an adaptive trait like total tick count. Lamb survival was unaffected by breed. When meat traits were considered, it was evident that Dorper lambs outperformed their Namaqua Afrikaner contemporaries for important attributes associated with size and meat yield, namely carcass weight and dressing percentage. Dorper carcasses also attained better grades and were more tender according to instrumental measurements (Warner Brazler equipment). Dorper lambs were fatter than Namaqua Afrikaner lambs, as derived from the backfat thickness at the 13th rib and the rump. While leaner meat would be preferred by health-conscious consumers, it is important to note that, under the conditions of the study, Dorper carcasses were more likely to be in the preferred grades. In the second part of the study, Dorpers were evaluated against the SA Mutton Merino (SAMM; the most numerous dual-purpose breed in South Africa), as well as the reciprocal cross between the two breeds. No conclusive breed differences were found for weight traits, lamb survival, tick counts or meat traits. However, there was a suggestion that lamb survival of Dorpers was higher than that of their SAMM contemporaries (P = 0.08), but significance could not be demonstrated. Crossbred progeny outperformed the midparent value by 6.3% for weaning weight. The corresponding study on meat traits was constrained by low numbers. However, it was evident that the observed heterosis for weaning weight was also present a later growth stage. Direct heterosis estimates amounted to 7.7% for slaughter weight and 7.1% for carcass weight. These estimates were consistent with the literature for the expected level of heterosis for early growth when assessed in fairly divergent sheep breeds. This outcome once again reiterated that crossbreeding may have a definite role to play at the commercial level in the South African sheep industry. Further studies on the comparison of indigenous genetic resources with commercial breeds, as well as crossbreeding studies with the variety of available breeds were recommended.Item Open Access Effect of different cryodiluents on Nguni bull semen viability and in vitro fertilizing capacity(University of the Free State, 2010-11) Mohapi, Maliengoane Rebecca; Lehloenya, K. C.; Greyling, J. P. C.; Nedambale, T. L.This study was aimed at evaluating the effects of different extenders and cryoprotectants on the quality of Nguni bull semen after cryopreservation, and to evaluate the performance of frozen-thawed Nguni bull semen in IVF. The study was conducted at ARC-Animal Improvement Institute in Pretoria, in conjunction with the University of the Free State from April to October 2008. Three Nguni bulls (average age of 5 years) were used, and the semen collected from each bull, twice a week, using an electroejaculator. The semen quality parameters were evaluated prior and post freezing. The parameters evaluated included sperm motility rate and percentage live sperm, semen pH and semen concentration. The semen samples collected were divided into three equal portions following every collection and allocated to three groups - based on the semen extender used. One portion was extended with egg yolk citrate, the other extended with egg yolk Tris, while the other sample was left undiluted and served as a control. Following the addition of the extenders, the semen samples were incubated for a period of 9h. Evaluation of semen quality parameters was done at 3h intervals, within that incubation period of 9 h. The egg yolk Tris extender exhibited a reduction in performance in terms of the sperm motility rate and the percentage live sperm, compared to the egg yolk citrate extender after 6 and 9h of incubation respectively. Thus the diluted semen was not further used in the second experiment. The semen samples extended with the egg yolk citrate diluents were incubated at different temperature regimes (50C and 250C) for a period of 12h, to evaluate the effect of temperature on the sperm quality of the diluted semen. In the second trial, the semen sample that was diluted with egg yolk citrate was further divided into three portions - in order to add three different cryoprotectants, namely glycerol, dimethyl sulfoxide and ethylene glycol. The percentage live sperm and the sperm motility rate of the semen sample following addition of the cryoprotectants were also evaluated after 2h of incubation but prior to freezing. The semen samples were then loaded into 0.5ml semen straws, which were sealed with polyvinyl alcohol. The semen straws were then placed in a programmable freezer for 40 minutes for semen cooling from an initial temperature of 50C, to a temperature of -1300C. After freezing the straws were removed from the programmable freezer and placed in liquid nitrogen vapour in a styro-foam box, for 5 minutes to cool the semen straws from -1300C to -1960C, after which the straws were plunged directly into liquid nitrogen (-1960C) tank, for storage until thawing. A total of 1560 bovine oocytes were retrieved by aspiration from 127 ovaries collected from Strydfontein abattoir in Pretoria. The oocytes were then matured in vitro in bovine maturation media (consisting of TCM 199, FSH, LH and estradiol), for a period of 24h. After 24h of incubation, the matured bovine oocytes with expanded layers of cumulus cells were washed in a BO-IVF solution and fertilized in vitro using frozen-thawed Nguni bull semen from the first trial, while the others were fertilized with fresh Nguni bull semen, used as a control. For IVF, mature oocytes were incubated with semen for 18h. Thereafter, the presumptive zygotes were vortexed in TCM 199 for 90 seconds in order to remove the cumulus cells. After that, the presumptive zygotes from each treatment were randomly allocated into two different culture media namely, KSOM and SOF. The control group, that is the fresh semen group (n=481), 242 zygotes were allocated to KSOM culture media, while 239 zygotes were allocated to SOF culture media containing BSA. The treatment group, that is the frozen-thawed semen (n=559), 280 zygotes were allocated to the KSOM culture media, while 279 zygotes were allocated to SOF- BSA culture media. The presumptive zygotes were then allowed to develop (incubated) for 7 days until reaching the blastocyst stage. On day 2 following IVC (onset of IVC = day 0), cleavage rate was evaluated, the presumptive zygotes at 2-4 cell stage and those at 8 cell stage were evaluated under a contrast microscope and development recorded. Thereafter, on days 2 and 5 of culture the culture media were changed. KSOM-step 1 was changed to KSOM-step 2, while SOF-BSA was changed SOF-FBS. On the 7th day the expanded blastocysts were evaluated and recorded. Extended semen exhibited a significantly (P<0.05) lower sperm concentration, than undiluted semen. The semen pH values were significantly (P<0.05) different at 0 to 3h of incubation between the treatment groups. After a period of 6h of incubation, no significant differences were recorded between the treatment groups, in terms of the semen pH. The semen pH was found to be acidic, however it became neutral after 9h of incubation in the semen sample that was diluted with egg yolk citrate extender and incubated at 50C. The percentage live sperm was similar for semen extended with egg yolk citrate and egg yolk Tris extenders incubated at 50C up to a period of 6h of incubation. Thereafter the percentage live sperm decreased in the semen sample extended with egg yolk Tris diluents, after a period of 9h of incubation (50C). The sperm motility rate was similar between the treatment groups up to 3h of incubation at 50C. After 6 and 9h of incubation (50C), there was a drastic decline in the sperm motility rate of the semen samples extended with an egg yolk Tris extender. The percentage live sperm and pH values differed significantly (P<0.05) following addition of a cryoprotectant. The semen sample in which glycerol was used (75±5.3%) exhibited a significantly (P<0.05) higher sperm survival rate, compared to the semen sample in which ethylene glycol was used (55±8.5%). Semen sample in which glycerol was used as a cryoprotectant (6.6±0.2) exhibited a significantly (P<0.05) higher pH, compared to the semen sample in which dimethyl sulfoxide was used as a cryoprotectant (6.3±0.3). The semen samples diluted at 50C exhibited a significantly (P<0.05) higher sperm concentration immediately following dilution, compared to samples diluted at 250C. The sperm motility rate immediately following dilution was similar between the treatment groups. However, the sperm motility rates at 3, 6, 9 and 12h of incubation were significantly (P<0.05) different (67±10% vs. 55±24%; 60±12% vs. 47±25%; 47±20% vs. 38±25% and 40±20% vs. 28±27%) at 50C and 250C respectively. The percentage live sperm was found to be similar between the treatment groups, up to 9h of incubation. However, after 12h incubation the semen sample incubated at 50C exhibited a significantly (P<0.05) higher percentage live sperm, compared to the sample incubated at 250C (46±21% vs 35±31%). The interaction between incubation temperature and the semen extender used did not affect all the measured sperm quality parameters. In vitro fertilization of cow oocytes with the frozen-thawed bull semen exhibited a significantly (P<0.05) higher percentage of presumptive zygotes at the 2-4 cell stage, compared to the use of fresh semen (32.1±13.0% vs. 24.3±12.8%). IVF with fresh semen (23.2±16.5%) resulted in a significantly (P<0.05) higher percentage of day 7 blastocysts, compared to the use of frozen-thawed semen (14.2±11.9%). Culturing of the presumptive zygotes with KSOM media (23.2±17.5%) exhibited a significantly (P<0.05) higher percentage of day 7 blastocysts, than culturing with SOF media (14.2±10.4%) in vitro. In conclusion, egg yolk citrate proved to be the best extender for diluting Nguni bull semen. Fresh Nguni bull semen diluted with egg yolk citrate can probably be incubated up to a period of 9h at 50C, without any detrimental effect on the percentage live sperm and the sperm motility rate. Nguni bull semen can be best frozen using glycerol as a cryoprotectant. Frozen-thawed Nguni bull semen can be successfully used in IVEP since it resulted in higher percentage of the presumptive zygotes at the 2-4 cell stage and also attained day 7 blastocysts. Frozen-thawed Nguni bull semen can also be used successfully within 60 minutes following thawing incubated at 50C. Nevertheless, fresh Nguni bull semen can still be used successfully for IVF purposes since it resulted in a higher percentage of day 7 blastocysts, compared to frozen-thawed semen. KSOM medium proved to be a better IVC medium for bovine semen than SOF medium in terms of the percentage of day 7 blastocysts obtained.Item Open Access Effect of dietary lipid saturation on layer production and egg quality(University of the Free State, 2012-07) King, Ernest John; De Witt, F. H.; Van der Merwe, H. J.; Hugo, A.English: A study was conducted to investigate the effects of dietary lipid saturation on nutrient digestibility, egg production and egg quality characteristics of laying hens during peak production (≤ 42 weeks of age). Five isoenergetic (12.6 MJ AME/kg DM) and isonitrogenous (170 g CP/kg DM) diets were formulated with a 30 g/kg lipid inclusion level, using a blend (50 / 50) of fish- and linseed oil (control n-3), pure fish oil (polyunsaturated n- 3), sunflower oil (polyunsaturated n-6), high oleic acid (HO) sunflower oil (monounsaturated n-9) and tallow (saturated fatty acid treatment). The blend of fish- and linseed oil blend were used to increase the α-linolenic acid content of the control n-3 diet, while fish oil was used in the polyunsaturated n-3 diet to increase the concentration of eicosopentaenoic- (EPA) and docosahexanoic acid (DHA) fatty acids primarily. Sunflower oil and HO sunflower oil was used to increase the linoleic- and oleic acid in the polyunsaturated n-6 and monounsaturated n-9 diets respectively, whereas tallow was used to increase palmitic- and stearic acid levels in the saturated fatty acid (SFA) treatment. Two hundred, individually caged Hy-Line Silver Brown hens (20 weeks of age) were randomly allocated to the five dietary treatments (n = 40 replicates/treatment) and received the respective experimental diets. During 24, 28, 32, 36 and 40 weeks of age, all eggs produced were recorded, individually weighed and used for analysis of internal and external egg qualities. While feed intake of hens was measured weekly, body weights were determined monthly. Data for the respective collection weeks were pooled for calculation of parameter means during statistical analysis. During the mentioned weeks eggs were evaluated for shell quality and internal egg quality. During week 30 of age, 12 eggs per treatment were also randomly selected for analyses of fatty acid methyl esters (FAME), thiobarbituric acid reactive substances (TBARS) and peroxide value (PV) while another 12 eggs were stored at 4oC for analyses after 28 days. At the end of the study (42 weeks of age) six birds per treatment were used to determine the effects of dietary lipid saturation on nutrient digestibility. Dietary lipid saturation had no effect (P > 0.05) on feed intake as well as most of the nutrient digestibility coefficients, except in the case of crude protein (P < 0.05) and fat (P < 0.0001), whereby the monounsaturated n-9 diet resulted in the highest (P < 0.05) CP digestibility which differs statistically only with that of the polyunsaturated n-6 diet, but not with any of the other dietary treatments. Therefore, no clear influence of dietary lipid saturation on apparent digestibility of CP could be detected. Furthermore, all poly- and monounsaturated diets had a higher fat digestibility (94.2 to 95.6%) than the SFA diet (90.4%). Although both the polyunsaturated n-6 and control n-3 treatments had the lowest (P < 0.01) apparent metabolisable energy (AME) and AME corrected for nitrogen (AMEn) values, no clear trend regarding dietary lipid saturation on nutrient digestibility could be established. Similarly to nutrient digestibility results, dietary lipid saturation resulted in a limited significant response on production parameters tested without any recognisable trends. The SFA treatment resulted in the lowest (P < 0.015) percentage sellable eggs, while feed efficiency (P < 0.001) and percentage eggshell (P < 0.05) was the lowest for the monounsaturated n-9 and polyunsaturated n-6 treatments respectively. Evaluating internal egg qualities, the control n-3 and polyunsaturated n-3 treatments had the lowest (P < 0.0001) egg yolk colour compared to that of the SFA which resulted in the highest colour score. Additionally, the FAME of egg yolk was successfully altered to represent that of the particular dietary treatment without any detrimental effects on the total fat content (P = 0.24), fat free dry matter (P = 0.17) or moisture (P = 0.66) content of egg yolk. The polyunsaturated n-3 treatment was highly effective (P < 0.0001) in increasing the EPA and DHA concentration of egg yolk, whereas a general increase in the dietary n-3 content resulted in a decreased (P < 0.0001) ratio of n-6 / n-3 for both the control n-3 and polyunsaturated n-3 diets. Both the SFA and monounsaturated n-9 treatments resulted in the lowest (P < 0.0001) TBARS for both time periods, whereas the polyunsaturated n-3 treatment resulted in the highest (P < 0.001) TBARS for both fresh and stored eggs (0.27 mg malonaldehyde / kg yolk during both time periods). From the results of the current study it can be concluded that although fat digestion was lower for the SFA treatment, AME values did not differ between treatments. With the exception of the SFA treatment that resulted in less sellable eggs, no influence of lipid saturation on egg production and external egg shell qualities could be detected. The results showed that PUFA n-3 diets could be successfully used to enrich the essential n-3 fatty acids of eggs. However, lipid oxidation stability as well as yolk colour was negatively influenced by an increase in PUFA n-3 type fatty acids.Item Open Access The influence of body mass on production characteristics of broiler breeders(University of the Free State, 2006-05) Phitsane, Pulane Mirriam; Van der Merwe, H. J.; Hayes, J. P.English: A study was conducted to investigate the effect of variation in body weight (BW) of broiler breeder hens at onset of lay (23 weeks of age) on subsequent egg production parameters and eggshell quality (27 to 60 weeks of age). Ross broiler breeder hens (n = 198) reared under restricted feeding were randomly placed in individual cages at 23 weeks of age. Hens were divided into low (LBW), medium (MBW), and high (HBW) body weight groups as follows: 2007 - 2447 g, 2645 - 2777 g and 2975 - 3445 g, respectively. The production parameters were recorded on a three weekly interval during the experimental period. The hens in the HBW group laid eggs that were significantly (P<0.05) heavier than hens in the other two groups during the initial stages of lay (27 to 30 weeks of age). The HBW hens had a statistically (P<0.05) higher egg content in comparison to the other two groups only during the first production interval (week 27 of age). Egg production was not significantly (P>0.05) affected by BW at the onset of lay. HBW hens at the onset of lay resulted in a higher mean egg output (P=0.0071) from the commencement of lay up to 36 weeks of age. HBW hens laid eggs with thicker broad and equator ends than the MBW and LBW hens during the first 10 weeks of lay. No statistical differences (P>0.05) were observed in shell percentage, shell per unit surface area and egg surface area between the different BW groups. BW variation significantly affected shell weight from 27 to 60 weeks of age, as high BW was associated with heavier shell weight. The results suggest that a high BW at the onset of lay plays a positive role on the performance (egg weight, egg output, egg content and eggshell thickness) of laying broiler breeder hens during the initial stages of lay. In a second trial the effect of BW at the onset of lay on calcium retention and excretion of broiler breeder hens during the different stages of lay was investigated. Ninety randomly selected hens from the broiler breeder hens as described in the first paragraph were used in the investigation. The experiment was conducted for a period of 15 weeks (27 to 42 weeks of age). Excreta samples were collected during a 7-day collection period at weeks 27, 33, 36, and 42 of age. The hens in the HBW group excreted a significantly (P<0.05) higher amount of calcium into the eggshells than the LBW and MBW hens with exception of week 27-33 of age; this was related to a higher daily calcium intake by the HBW hens though calcium intake did not differ statistically (P>0.05). No significant differences were observed in calcium retention, faecal calcium excretion and total calcium excretion among the BW groups throughout the 15-week period of the trial. It seems that calcium homeostasis was maintained by the broiler breeder hens irrespective of the BW status at the onset of lay. It was concluded that BW of the hens at the onset of lay as a point of reference for subsequent egg production and eggshell quality is probably not sufficient. Other factors like change in BW grouping over the laying period and energy requirements of the hens may also be important to consider.Item Open Access Characterization and cryopreservation of South African unimproved indigenous goat semen(University of the Free State, 2010-05) Matshaba, Bright; Schwalbach, L. M. J.; Greyling, J. P. C.; Nedambale, T. L.Semen from 7 South African unimproved indigenous bucks that were successfully trained from a group of 10 bucks for semen collection with the aid of an artificial vagina (AV) was characterized and then cryopreserved, using different semen extenders. Semen was collected twice a week and evaluated macroscopically for ejaculate volume and pH immediately after collection. Within 1h of collection, semen was further analysed electronically for sperm concentration. Thin semen smears were stained with eosin/nigrosin and evaluated under a fluorescent microscope for viability (percentage live or dead) and morphology (percentage normal or abnormal). In addition semen samples were evaluated using the computer assisted sperm analysis (CASA) for sperm motility (static, non progressive and progressive), velocities (static, slow, medium, rapid, VCL, VSL and VAP) and linearity (LIN, STR and WOB) parameters using a Sperm Class Analyser® (SCA®). Four different semen extenders, namely: Tris-1.5% yolk, Tris-15% BSA, Ovixcell® and Bioxcell® (IMV, L’Aigle, France) were used to cryopreserve pooled semen samples, with and without 6% glycerol thus making a total of 8 treatments. Immediately after dilution and after thawing, semen samples were compared through the evaluation of viability, morphology, motility, velocity and linearity parameters, using the same methodology used for fresh semen. Semen was then incubated at 37ºC and analysed for motility and velocity parameters after 30 and 60 minutes of incubation. Regarding the fresh semen samples, the South African unimproved indigenous bucks recorded an overall average ejaculate volume of 0.5 ± 0.2 ml, pH of 7.5 ± 0.2 and sperm concentration of 681.7 ± 74.6 x 106 sperm/ml. On average, bucks recorded 79.0 ± 6.3% normal and 76.3 ± 8.2% live sperm cells in the ejaculates. The average percentage of sperm abnormalities on head, mid-piece and tail were 4.2 ± 1.3%, 4.6 ± 1.7%, and 12.1 ± 5.4%, respectively. The overall sperm abnormalities recorded were 1.0 ± 0.8%, 9.5 ± 2.9% and 10.1 ± 3.6% for primary, secondary and tertiary abnormalities, respectively. The mean static, nonprogressively motile (NPM), progressively motile (PM), slow, medium and rapid sperm cells recorded were 30.9 ± 14.7%, 32.1 ± 10.9%, 37.3 ± 10.0%, 4.9 ± 1.7%, 6.0 ± 1.7% and 58.2 ± 14.1%, respectively. Viability of goat sperm following fresh semen dilution with the four different semen extenders was similar, however a reduction of approximately 20% in the percentage live and normal sperm was recorded (5-10 minutes after dilution), when compared to the fresh undiluted pooled semen sample. Similar motility parameters were recorded shortly after fresh semen dilution using the 4 different extenders. A slight decrease of approximately 4% in the extended semen’s sperm motility was observed, when compared to that of fresh undiluted semen. For the sperm velocity parameters, semen extended in Tris-BSA showed significantly higher medium sperm velocity. Following freezing-thawing, a drastic reduction in the percentage live and normal sperm was recorded in all treatments. Bioxcell® without glycerol recorded the highest number of live and normal sperm. The Bioxcell® and Ovixcell® extenders recorded the highest percentage linearity and straightness movement of the sperm. In general, cryopreservation reduced the sperm cell viability and motility parameters. In addition no effect of extender on the morphology of South African unimproved indigenous buck sperm was observed. Sperm motility and velocity results showed that sperm extended in Bioxcell® and Ovixcell® recorded higher values immediately post-thawing, while the Tris-based extenders recorded the highest values after 30 minutes of incubation, before declining rapidly. The South African unimproved indigenous bucks seem to produce a lower semen volume (ejaculate), sperm concentration, and percentage progressively motile sperms, compared to the European, Asian and Boer goat breeds. The results demonstrate that Bioxcell and Ovixcell are suitable extenders to induce high post-thawing viability, motility and velocity of buck sperm.Item Open Access Factors affecting productive life and fertility in Nguni cows(University of the Free State, 2017-07) Ngayo, Mawande; Fair, M. D.; Neser, F. W. C.; Scholtz, M. M.English: The objective of the study was to assess factors that affect productive herd life and fertility in the Nguni cows using different models. The data set was obtained through the SA Stud book Logix information system. Cattle in the data were registered Nguni cows with their pedigree information from three herds reared extensively in three different environments in South Africa. The raw data included animal identity numbers born between 1968 and 2015, with sire, and sire of sire, dam of sire, dams, sire of dam and dam of dam. One herd had 12 788 animal identity records, the second one had 6 929 and the third one had 8 421 identity records. Amongst other important things included in the original data are the birth dates of each animal, culling date, death date, inspection date, registration date, breeder number, owner number and ownership date. Necessary edits were done to prepare data for analysis. The age at first calving and inter-calving period were used as traits to assess productive herd life length. Age at first calving was calculated as the difference between birth date and first calving date in days. The inter-calving period was calculated as the difference between two successive birth dates. First analysis was done for productive herd life on the combined data of all three herds using animal models through ASREML program. For the combined data all effects fitted in the model were significant (P<0.05). The mean obtained for age at first calving (AFC) and inter-calving period (ICP) was 893.5 and 408.4 days, respectively. The minimum and maximum age at first calving (AFC) was 512 and 1 099 days, respectively. The minimum and maximum ICP was 313 and 800 days, respectively. The mean, minimum and maximum number of parities (NP) was 7.2 and 15, respectively. Productive herd life (HL) mean and standard deviation was 2 542 and 1 272 days, respectively, with a minimum and maximum of 655 and 6 088 days, respectively. The variance components were 770.7, 2 7196 and 1 103, respectively for additive genetic effects, phenotypic effects and residual and the heritability (h2) and standard error was 0.028 and 0.04, respectively. The analysis was also carried out on separate herds using ASREML. The mean for AFC in all three separate herds was 848.1, 893.4 and 918.5 for Komga (KM), Perdeberg (PG) and the Vaalharts (VH) herd, respectively. The minimum AFC was 512, 602 and 534 for KM, PG and VH, respectively and the maximum AFC was 1 099 for all three herds. The mean for inter-calving period (ICP) was in the KM, PG and VH herd was 404.5, 403.5 and 404.2, respectively. The minimum AFC was 329, 315 and 313 in the KM, PG and VH herd. The maximum AFC in the KM, PG and VH herd was 701, 655 and 800, respectively. Variance components for the direct additive effects, phenotypic and residual effects were 19 801, 1 508.2 and 1 743.2, respectively in the KM herd. In the PG herd the variance components were 0.1950, 36 339 and 2 731.4, respectively for the direct additive effects, phenotypic and residual effects. The variance components in the VH herd for direct additive, phenotypic and residual effects were 19 048, 582.98 and 1 220.4, respectively. The heritability estimate was 0.08, 0.00 and 0.03, respectively in the KM, PG and VH herd. Age at first calving (AFC) and inter-calving period (ICP1 and ICP2), were used as traits to assess cow fertility using linear multiple trait animal models of ASREML and repeatability model. The inter-calving period was used as the repeated trait in the model. The mean for AFC was 896.8. Minimum and maximum age was 512 and 1 230days, respectively. For the first inter-calving period (ICP1) the mean was 423 days, while the minimum and maximum was 270 and 823 days, respectively. The second inter-calving period (ICP2) obtained a mean of 400.3 days, with minimum and maximum of 275 and 810 days, respectively. Variance components for AFC were 6 476.6, 18 238 and 11 762, respectively, respectively for direct additive effects, phenotypic effects and residual and the heritability was 0.36. ICP1 yielded 1 139.8, 10 691 and 9 551.5, respectively for direct additive effects, phenotypic effects and residual with a heritability estimate of 0.11. For ICP2 1 890.1, 8 520 and 6 630.1, respectively were variance components for direct additive effects, phenotypic effects, residual; with a heritability estimate of 0.22. The correlation estimate between AFC and ICP1 was 0.58, and it was 0.59 between AFC and ICP2. ICP1 and ICP2 had a correlation estimate of 0.12 between them. For the repeatability model, the variance component values for ICP used as the repeated trait were 381, 8 155.8 and 7 774.8, respectively for direct additive effects, phenotypic and residual effects. The heritability and repeatability estimate was 0.05 and 0.22, respectively. The Nguni cow productive herd life was analyzed using the Survival kit V3.12 (Ducrocq & Solkner, 1998) featured models. The Cox model which is the semi-parametric model featured in the Survival kit was used to analyze the Nguni cow data. The Nguni cow herd herd data set analyzed using the Cox model had 1 245 cow records starting from year 1996 to 2015 with parities from one up to the 9th parity. Animal records for cows in the productive herd between the 1st of January 1984 and 31 December 1995 were truncated because of lack of information on the culling or death date. The cow herd was stratified into 3 groups of ages at first calving (18, 24 and 36 months). This likelihood risk ratio results indicated that year, AFC and parity were significant (P<0.05). The model yielded a heritability estimate of 0.02 and a standard error of 0.003. Risk ratios for culling differed for different ages at first calving (18, 24 and 36 months AFC), over the years (from 1996 to 2015) and at different parities (from the 1st to the 9th parity). For 24 months AFC the culling risk ratio was the least compared to 18 and 36 months age at first calving. Heifers that had their first calf at 18 months age were at a 0.061 risk of being culled, whereas the ones that had their first calf at 24 months were at a 0.042 probability of being culled. For heifers that calved for the first time at 36 months age the culling risk ratio was 1.000. In the year 2015 about 250 cows were culled which was more than any other year included in the study. More animals were culled in their 9th (120 cows) and the least number was culled in their first parity (4). Only 4 cows were culled in the group of cows that had their first calf at 18 months, 27 were culled in the group of cows that had their first calf 24 months and 95 were culled in the group that had their first calf at 36 months of age.Item Open Access Feedlot performance of Dorper lambs on Opunti: based diets with different nitrogen sources(University of the Free State, 2009-11) Shiningavamwe, Katrina Lugambo; De Waal, H. O.; Schwalbach, L. M. J.; Els, J.Three feedlot diets were evaluated with Dorper wether lambs at Bergvlug Experimental Farm, Khomas Region, Namibia. Bergvlug is located about 35 km east of Windhoek. The three treatment diets consisted of a conventional feedlot diet (treatment diet T0) and two Opuntia-based treatment diets (T1 and T2) containing different additional nitrogen sources, namely a non-protein nitrogen (NPN; feed grade urea) or natural protein (sunflower oilcake meal). Treatment diet T0 was based on coarsely ground lucerne hay, yellow maize meal, feed grade urea and molasses meal. The Opuntia-based treatment diets (T1 and T2) were reformulated and part of the lucerne was replaced by sun-dried and coarsely ground Opuntia cladodes at levels of 330 or 300 g/kg. In treatment diet T1 additional nitrogen was included as feed grade urea (non-protein nitrogen; NPN) and for treatment diet T2 the additional nitrogen was included as sunflower oilcake meal (a natural protein). The feed intake and water intake, the growth performance and carcass characteristics of the Dorper wether lambs were evaluated in the feedlot. Forty-five newly weaned Dorper wether lambs, weighing on average about 22 kg, were randomly allocated to the three treatment diets. The 15 Dorper wether lambs per treatment diet were further subdivided into three subgroups or replicates of five lambs each. For the duration of the trial the lambs were kept in small pens in a shaded area (open-sided roofed shed). The Dorper wether lambs were fed the treatment diets until a target average slaughter weight of 35 kg per treatment diet was reached. During the feeding period in the feedlot, one replicate of five Dorper wether lambs per treatment diet was moved from the feedlot pens to metabolism cages for a week every third week to determine their individual daily feed and water intake and apparent digestibility of the three treatment diets. The daily urine and faecal excretions were also monitored. Chemical analysis of the three treatment diets used in this study showed that acid-detergent fibre (ADF), neutral-detergent fibre (NDF), organic matter (OM) and gross energy (GE) have decreased with inclusion of sun-dried and coarsely ground Opuntia cladodes, which is ascribed to the lower ADF, NDF, OM and GE content of the Opuntia cladodes. On the other hand, the ash and lipids increased with inclusion of sun-dried and coarsely ground Opuntia cladodes in the treatment diets. The inclusion of sun-dried and coarsely ground Opuntia cladodes at 330 or 300 g/kg in the treatment diets in general had little or no effect on the feed intake and digestibility of the treatment diets by Dorper wether lambs. Exceptions were observed for the intake and apparent digestibility of ADF and NDF as a result of the difference in fibre content of the treatment diets. Similar water intake and urine excretion were observed for Dorper wether lambs fed any one of the treatment diets during the three cage feeding periods. The results of the study confirmed that the feed intake and apparent digestibility of the treatment diets for Dorper wether lambs were not affected by: (1) the inclusion of sun-dried and coarsely ground Opuntia cladodes at 330 and 300 g/kg; or (2) two nitrogen sources used (NPN or natural protein) in the Opuntia-based diets. Considering the results of the Cage Periods 1 to 3, it can be summarised that the daily intake and apparent digestibility of DM and other chemical constituents of the Dorper wether lambs increased as the trial progressed, regardless of the treatment diets. It suggests that the reticulo-rumen of Dorper wether lambs were getting better adapted over time to the diets and consequently digestibility improved. The average daily gain and feed conversion efficiency of Dorper wether lambs fed the Opuntia-based diet supplemented with natural protein were comparable to those fed the conventional feedlot diet. The Dorper wether lambs fed the Opuntia-based diet supplemented with NPN had a lower growth rate than those fed the conventional feedlot diet and the Opuntia-based diet supplemented with natural protein. Thus, although feed conversion efficiency was not significantly (P>0.05) different among treatment diets, Dorper wether lambs fed the conventional diet and the Opuntia-based diet supplemented with natural protein required less feed to gain weight than those fed the Opuntia-based diet supplemented with NPN. This suggests that supplementing an Opuntia-based feedlot diet with a natural protein source will markedly improve feed efficiency and average daily gain of lambs. This may reduce the feeding period required to reach the target slaughter weight and increase the economic benefit associated with the use of sun-dried and coarsely ground Opuntia cladodes in feedlot diets. Most of the carcass characteristics considered were not significantly different (P>0.05) among treatments. It suggests that carcass quality or grading is not markedly affected by inclusion of sun-dried and coarsely ground Opuntia cladodes in feedlot diets (up to 330 or 300 g/kg) for Dorper wether lambs or by the nitrogen source used to balance the diets. The carcasses of the Dorper wether lambs fed the three different treatment diets fetched very similar prices per kg. However, the Dorper wether lambs fed treatment diet T1, the Opuntiabased diet with the inclusion of feed grade urea (an NPN source), did not reach the average target slaughter weight of 35 kg, even after 91 days in the feedlot. Therefore, their lighter carcasses and poorer carcass grading at slaughter fetched a lower total price per carcass. The results of this study, the fourth study under the auspices of the UFS, opened the prospect of formulating affordable Opuntia-based diets for specific application to ruminant species of different ages and production classes. However, more research is needed to evaluate the growth performance, carcass characteristics and profitability of other small stock breeds and ruminant species fed sun-dried and coarsely ground Opuntia cladodes in feedlot diets, balanced with different nitrogen sources.Item Open Access Physical form of maize grain in finishing rations of ram lambs(University of the Free State, 2008-05) Zietsman, Renier; Van der Merwe, H. J.English: The effect of whole (WMG), ground (GMG) and fine (FMG) maize grain in finishing rations for lambs containing 20 and 40% lucerne hay respectively was investigated. Thirty 3-month-old SA Mutton Merino lambs were randomly allocated to 6 treatments of 5 animals each. A digestibility and production study was carried out (60 lambs in total). All lambs were kept in individual pens for the duration of the various studies. The dry matter intake (DMI) of the lambs in the digestibility study consuming the ration with WMG was significantly (P=0.0052) lower than those fed FMG. Processing of maize grain resulted a significant (P<0.05) reduction in the apparent digestibility of dry matter, crude protein, acid detergent fibre and gross energy as well as digestible crude protein and metabolisable energy (ME). In contrast with DMI (P>0.05) the apparent digestibility of dry matter, crude protein and gross energy were significantly (P<0.05) decreased with an increase in roughage level to 40%. Acid detergent fibre digestibility showed no statistical significant (P>0.05) differences between dietary roughage levels. Lucerne hay level did not influence (P>0.05) the ME-content of the finishing rations within a specific physical form. Physical form of maize grain in finishing rations for lambs did not significantly (P>0.05) influence DMI, feed conversion and carcass characteristics. The inclusion of FMG in a finishing ration with 40% lucerne hay resulted in a significant (P=0.0013) lower MEintake. A significantly (P<0.05) poorer weight gain and energy efficiency were observed for lambs fed WMG in the ration. The inclusion of 20 and 40% lucerne hay in finishing rations of lambs did not significantly (P>0.05) influence DMI, ME-intake and weight gain as well as feed and energy efficiency. A higher (P<0.05) carcass weight and dressing percentage occurred when 20% compared to 40% lucerne hay was included in the lamb-finishing ration. It was concluded that the physical form of maize grain in finishing rations has no influence on the performance of lambs. Accordingly no physical form x roughage level (20 to 40% lucerne hay) interaction exists in finishing rations for lambs.Item Open Access Feeding ecology of the greater Kudu (Tragelaphus strepsiceros) in the central Free State(University of the Free State, 2017-02) Butler, Vivian Page; Janecke, B. B.; Smit, G. N.The objective on most wildlife ranches is to accommodate a diversity of wildlife species to satisfy the need for ecotourism, hunting and live sales. However, the small size of many wildlife ranches presents its own unique challenges. One of these is fencing that prevents animals from moving to more favourable areas during times of food shortages. Intensive management is thus required to prevent overstocking that can lead to the deterioration of natural resources or even total habitat destruction in the long term, or alternatively requires the provision of supplementary feed at a high cost over an extended period of time. The feeding habits of herbivores are largely determined by their food preferences and the availability of their preferred food plants, with food considered the most important resource that limits animal populations. It is thus important that an animal’s diet provides all the essential nutrients needed for survival, growth and reproduction. However, the quality and quantity of food available to herbivores can vary considerably from one season to the next or from year to year. A proper management plan is therefore essential for the sustainable utilisation and conservation of the ecosystem on these small fenced wildlife ranches. The main objectives of this study were to determine the diet and food preferences of kudu throughout the seasonal cycle of food availability and how this affected their habitat selection in a relatively small game fenced area in the central Free State. The potential food available to kudu was first determined in each of the identified plant communities and then in the study area as a whole. As kudu are predominantly browsers, only the woody browse (leaves + shoots < 0.5 cm) up to a feeding height of 2.0 m was considered to be available to kudu in the current study. Forbs were not included as they were rarely encountered in the study area, contributing an insignificant proportion of the herbaceous layer. Leaf phenology of woody species was also taken into account in these calculations due to the winter deciduous nature of several woody species in the study area. The diet composition and food preferences of kudu varied according to food quality and availability. Although the kudu population’s annual diet consisted of mostly woody browse, a considerable amount of grass was consumed from November to March. Kudu also changed their diet selection from mostly deciduous woody species during the growing season to mostly evergreen species during the dry season. In addition to this, kudus’ food preferences changed throughout the year due to the timing of leaf emergence and leaf fall in woody species. Although the habitat selection of kudu was affected by food availability, cover also played an important role in determining their habitat preferences. Kudu showed a definite preference for areas with high woody canopy cover throughout the year, often trading food for more cover. Kudu habitat selection also changed markedly between day and night time, with kudu selecting areas dominated by their preferred food items during the day and areas with more cover, but less of their preferred food items at night. The selection of areas predominantly for feeding or resting was further confirmed by the fact that kudu were less active at night, as they travelled shorter distances during the night compared to the day. Topography also became important in the habitat selection of kudu during the coldest part of the year, with kudu escaping the worst cold by moving to the hills, especially at night when temperatures dropped to well below freezing point. Proper habitat analysis thus plays a crucial role in determining the suitability of fenced areas for kudu, as the availability of sufficient cover is just as important as the food available to these animals.Item Open Access The effect of NDF content in finishing diets on performance and meat quality of lambs(University of the Free State, 2016-02) De Klerk, Inalene; Einkamerer, O. B.; Hugo, A.; Greyling, J. P. C.English: A study was conducted to investigate the effect of incrementally increasing NDF levels of finishing diets on apparent digestibility, production performance, FA composition, oxidative stability and tenderness of lamb. The five dietary treatments were formulated to contain a similar nutrient composition, differing only in respect to the NDF content as the primary parameter. The NDF content increased from low roughage (primarily lucerne hay as fibre source) inclusion to a high roughage inclusion rate representing a dose-response trial in the following order: 12.76% (T15), 17.69% (T30), 22.53% (T45), 27.48% (T60) and 32.40% (T75) NDF/kg DM, respectively. No rumen modifiers or buffers were added to the diet. Sixty (60) South African Mutton Merino wether lambs (29.3±1.8 kg) were randomly allocated to the five dietary treatments (n=12 lambs per treatment) and further subdivided into 12 animals per replicate (n=1 lamb per replicate). After dietary adaptation of 10 days all lambs received the experimental diets for the remaining period (51 days). Live weight and feed intake were recorded on a weekly basis. A digestibility study was conducted over a 12-day period (4-day adaptation to the faecal bags followed by an 8-day collection period) where seven lambs (mean 48.11±2.94 kg live weight; total of 35 lambs) were randomly allocated to each treatment (n=7 lambs/treatment). At the end of the production study all lambs were slaughtered. Physical carcass characteristics, muscle and subcutaneous FA composition, meat oxidation (malonaldehyde content), colour stability, as well as meat tenderness were measured. The data was subjected to analysis of variance (PROC ANOVA) of the SAS program, version 9.2 (SAS, 2008). Tukey’s honest significant difference (HSD) test was used to identify significant differences (P <0.05) between treatments. From the results of the present study it is apparent that an incremental increase in the NDF content of lamb finishing diets presented a significant decrease (P <0.05) in DM, OM, NSC, GE, CP and EE digestibilities, as well as ash solubility. In addition, the significant (P <0.05) decrease in digestible OM, NSC and EE dietary content were associated with diet digestibility and resulted in a significant decrease (P <.0001) in ME content following an increased NDF incremental inclusion. A high roughage inclusion in finishing diets for lambs (T75) resulted in a significant (P <0.05) reduction in MEI, ADG, FCR, and therefore cold carcass weight and dressing percentage. Increased dietary NDF content significantly (P <0.05) increased saturated stearic acid, and significantly (P <0.05) decreased monounsaturated oleic and vaccenic acid, polyunsaturated linoleic acid, as well as total PUFA, n-6, n-6:n-3 and PUFA:SFA ratios of both lamb meat and adipose tissue. Apart from the NDF content significantly (P <0.05) affecting the monounsaturated palmitoleic acid (decreased) and polyunsaturated CLA (C18:2c9t11;n-6) content of muscle tissue, as well as total SFA (increased) and MUFA (decreased) content of only adipose tissue, the effect of dietary treatment between lamb deposit sites seem to be similar. Neutral-detergent fibre content did significantly (P <0.05) affect meat colour stability stored for 7 days at 4oC. Neutral-detergent fibre content had no effect (P >0.05) on meat tenderness. These results suggest that the FA profile of lamb can be manipulated by altering the NDF content of the finishing diet. This however did not result, from a human health point of view, in the desirable PUFA:SFA and n-6:n-3 ratios in muscle and subcutaneous lipid tissue. It is proposed that, to increase the total UFA content and its desirable effect on the mentioned ratios of lamb meat, regression equations should be used to establish the optimum response at a given NDF inclusion. Further research attempting to manipulate specific FAs (single or total) or FA ratios of lamb meat via dietary means to meet consumers’ demands need further attention.Item Open Access Quantification of bull sperm traits as measured by CASA and the relationship to pregnancy rate following controlled breeding(University of the Free State, 2017-05) Mphaphathi, Masindi Lottus; Nedambale, T. L.; Greyling, J. P. C.The biological importance of a bull’s contribution through artificial insemination to reproductive efficiency is of great importance because the sperm represents half of the genetic composition of its progeny. Therefore, the main objectives of the current study were: (1) To characterise, compare and evaluate fresh (raw) and frozen-thawed semen of both Bonsmara and Nguni breeds using computer aided sperm analysis (CASA) technology, (2) to compare the oestrous synchronization response and conception rate of Bonsmara, Nguni and Nguni type cows following fixed timed artificial insemination (FTAI) with Bonsmara or Nguni semen, and (3) to find the relationship between cows conception rate (in vivo and in vitro fertilization) and bull sperm motility rate (sperm traits) assessed by CASA technology following insemination regardless of bull breed. Electro ejaculator method was used to collect semen from Bonsmara (n = 4) and Nguni bulls (n = 4). Collected semen samples were evaluated for both macroscopic and microscopic traits.Following semen evaluation, the semen samples were either loaded into 0.25 or 0.5 mL straws and frozen using a programmable freezer. The semen straw was thawed at 37° C and analyzed by a CASA technology. In addition, purchased (from commercial AI center) frozen semen straws of Nguni and Bonsmara breed were also thawed. Sperm characteristics examined included total motility (rapid, medium and slow) progressive and non-progressive motility. Velocity characteristics included curvilinear and straight-line velocity, average path velocity, linearity, straightness, wobble, amplitude of lateral head displacement, beat cross frequency and hyperactive. During in vivo sperm fertility test, 100 Bonsmara, 452 Nguni and 94 Nguni type cows were randomly selected and subjected to oestrous synchronization protocol and FTAI with frozen-thawed assessed semen by CASA before FTAI. Briefly at Day 0, cows were inserted with an intravaginal CIDR® and removed on Day 7. Prostaglandin was then administered on Day 08 and a heat mount detector was placed on the hind quarter of each cow. In vitro sperm fertility test, collected oocytes from slaughterhouse were in vitro matured (n = 360) and in vitro fertilized (1 x 106 sperm/mL) in 100 μL droplets (final volume) of BO-IVF medium per treatment bulls (Bonsmara or Nguni bull). The frozen/thawed semen straws of Bonsmara and Nguni bulls were randomly selected and were used under the same IVF conditions. The microscopic of thawed bulls sperm characteristics were examined by CASA prior to in vitro fertilization. Data was analyzed using ANOVA. Treatment means were compared using the Fisher's protected t-test least significant difference. The average ejaculated semen volume of Bonsmara and Nguni bulls was 4.5 mL and 3.7 mL, respectively. The Bonsmara semen pH was 7.2 to 7.8 and Nguni semen 6.9 to 7.2, with an average value of 7.4 and 7.1 semen pH recorded, respectively. Individual variation ejaculates (raw semen) of the Bonsmara and Nguni bull’s total sperm motility traits (ranged from 86.5 to 93.9 % and 89.5 to 95 %, respectively) were recorded. Sperm cell concentration differed significantly among individual Bonsmara bulls (48.8 × 109 sperm/mL). Most of the ejaculates with live and normal sperm were above 85.3 % and 90.1 % in the Bonsmara and Nguni bulls, respectively. There was a significant difference on oestrous response for the Bonsmara (83.0 %), Nguni (90.8 %) and Nguni type cows (84.0 %), respectively. The Nguni type cows recorded a significant higher pregnancy rate (65.7 %), compared to the Bonsmara (59.0 %) and Nguni (37.1 %) breeds (P < 0.05). The sperm traits (TM, PM and RAP) were found to be positively correlated to conception rate (r = 0.06, 0.03 and 0.08, respectively). There was a significant difference on the average frozen-thawed sperm TM rate of ARC-Bonsmara (92.9 %), ARC-Nguni (92.2 %), CO-Nguni (85.2 %) and CO-Bonsmara (87.7 %). There was a positive correlation (r = 0.52) between oestrous response and pregnancy rate, for both Bonsmara, Nguni and Nguni type cows. There was a minimal fertilization rate following IVF with Bonsmara and Nguni breed bulls sperm. There was significant relationship on sperm TM and fertilization rate for both Bonsmara and Nguni breed. In conclusion, Nguni cows had the highest oestrous response compared to Bonsmara cows; however, the pregnancy rate was lower in Nguni cows. The sperm traits from both Bonsmara and Nguni bulls were found to be related to in vivo conception and in vitro fertilization rate when sperm cells were assessed by CASA technology.Item Open Access Die effek van die vervanging van vismeel met alternatiewe proteïenbronne in diëte van baber (Clarias gariepinus) litlinge(University of the Free State, 2008-05) Booysen, Rohan; De Toit, J. E. J.Afrikaans: Intensiewe visproduksie benodig voere met 'n hoë proteïeninhoud (Hecht, Uys & Britz, 1988). Voer is gewoonlik die grootste veranderlike koste-item in kommersiële produksie en daarom word die winsgewendheid van 'n intensiewe-produksie eenheid grootliks bepaal deur die beskikbaarheid en koste van voerproteïen. Vismeel is tradisioneel die grootste komponent van alle visvoere (Hecht, Uys & Britz, 1988). Die hoë koste van vismeel het gelei tot die soektog na alternatiewe proteïenbronne, veral die wat nie geskik is vir menslike inname nie. In die studie is ondersoek ingestel na die effek van die vervanging van vismeel met alternatiewe proteïenbronne in diëte van (Clarias gariepinus) baberlitlinge. Die volgende plantproteïenbronne is in die studie gebruik nl. sojaboonoliekoekmeel, spirulina, grondboonoliekoekmeel en katoensaadoliekoekmeel. Dit is opgeweeg teen 'n forelproduksierantsoen en 'n visdieet met vismeel as proteïenbron. Die sisteem wat opgestel is, was 'n geslote hersirkuleringseenheid wat uit dertig bakke bestaan. Die sisteem het 'n totale volume van +/- 800 liter water en die vloeitempo van die water in die sisteem was +/- S liter per minuut. Die temperatuur van die water is gehandhaaf op 28 +/- O.SoC.Driehonderd 10-week-oue babertjies is ewekansig verdeel tussen dertig bakke. Vyf bakke is toegedeel aan elke dieet m.a.w. ses rye met vyf bakke elk. Die totale biomassa is weekliks in elke bak geweeg en die voer is dienooreenkomstig aangepas. Die vissies is teen 2% van die totale biomassa gevoer vir die eerste vier weke en teen 3% vir die oorblywende vier weke. Die eksperiment is gestaak na 'n agt weke voerperiode. Wat groei betref is gevind dat die vissies wat die vismeeldieet ontvang het die hoogste gemiddelde massatoename van die ses diëte gehad het alhoewel huloorlewing nie baie goed was nie. Die mortaliteite van die vissies wat die spirulina-dieet ontvang het was egter die laagste van al die diëte. Dit was duidelik uit die studie dat vissies beter gegroei het op die vismeel dieet maar dat die wat die spirulina-dieet ontvang het weer meer bestand was teen strestoestande met gevolglik laer mortaliteite. Daar is dalk 'n moontlikheid om verskillende proteïenbronne te kombineer om optimale groei en weerstand teen strestoestande te bekom en sodoende die gebruik van vismeel as die enigste bron van proteïen in visdiëte te verminder. Verdere navorsing is egter nodig.Item Open Access A plant ecological study of the Rietvlei Nature Reserve, Gauteng Province(University of the Free State, 2004-11) Marais, Riaan; Smit, G. N.; Du Preez, P. J.English: This study was undertaken with the objective to identify and quantify different homogeneous management units on the Rietvlei Nature Reserve to facilitate more effective management as far as grazing utilization, burning and monitoring are concerned. Vegetation units had to be identified and mapped. From the communities different management units could be identified. The study area of 3 870 hectares is a proclaimed nature reserve and is situated southeast of Pretoria in the Gauteng Province. A phytosociological study of the vegetation was done using the Braun-Blanquet method. A total of 184 plots were sampled and classified using the Braun-Blanquet method and TWINSPAN. This study revealed that the vegetation of the Rietvlei Nature Reserve could be divided into six main communities, each with a number of sub-communities and some with variants. The communities identified were: Andropogon schirensis – Aristida congesta Community, Gladiolus crassifolius – Brachiaria serrata Community, Eragrostis chloromelas - Setaria sphacelata var sphacelata Community, Eragrostis chloromelas - Cynodon dactylon Community, Setaria verticillata – Phragmites australis Community and Arundinella nepalensis – Eleocharis dregeana Community. The different communities described were used as a basis for the representation of a vegetation map of the reserve and the demarcation of management areas for the Rietvlei Nature Reserve.Item Open Access Evaluation of techniques to determine the production potential of cultivated pastures(University of the Free State, 2009-12) Vermeulen, Sunet; Snyman, H. A.; Botha, P. R.English: For farm managers to utilize their pastures more efficiently, it is essential to estimate both herbage biomass and botanical composition. Therefore, there is a need to estimate herbage biomass and botanical composition of cultivated pastures with simple, accurate and cost-effective methods instead of the more accurate, but time-consuming destructive methods. The objective of this study was to evaluate non-destructive methods for estimating herbage biomass and/or botanical composition on different mixed-species pastoral systems for beef and/or dairy cattle and to identify the method, if any, that would be most accurate in each particular pastoral system. A comparison of the rising plate meter, the comparative yield method and the meter stick was conducted to determine the predictability of these non-destructive methods for estimating herbage biomass. Furthermore, the dry-weight-rank method for determining species composition was compared to hand clippings. The accuracy of the different non-destructive methods for estimating herbage biomass was compared using the coefficient of determination (r2) values between cut material and herbage biomass estimates. The study indicated that the meter stick (r2 = 0.79 – 0.85) provided the most accurate values for the dairy pastoral systems. In the beef pastoral systems the rising plate meter (r2 = 0.76 – 0.83) resulted in the most accurate method, for three out of four of pastoral systems. It was clear that species composition of the stand was an important factor affecting the accuracy of herbage biomass estimates. Based on the results of this study, all of the non-destructive herbage biomass estimation methods tested are suitable for use on both farm-level and pasture studies on larger areas. However, in grazing studies that are conducted on relatively small areas and with a relatively small number of animals, these methods may be less accurate and where accurate herbage biomass is desired, cutting is still recommended. Furthermore, the results indicate that the dry-weight-rank method of analysis is an accurate means of determining the botanical composition of both cultivated dairy and beef pastoral systems. The contribution of 92% and 96% of all species within the dairy and beef pastoral systems, respectively, was estimated within 5% accuracy of the “true/actual” value of species determined by hand clipping. These methods for determining herbage biomass and botanical composition can serve as a useful tool to set stocking rates at levels necessary to balance forage supply and demand in pastures that may have uneven species composition. These measurements are essential to make sure that animals are adequately fed and swards not under- or overgrazed and therefore ensure sustainable animal production.Item Open Access Food-related determinants of Kudu carrying capacity in a semi-arid savanna(University of the Free State, 2001-11) Van der Waal, Cornelis; Smit, G. N.English: A comparative study was conducted in order to investigate the relationship between forage availability and parameters of kudu populations thought to have a bearing on kudu carrying capacity in a semi-arid savanna. This involved eight game-fenced study units. The leaf production and standing crop of woody and forb species were determined. Woody species were classified according to rainfall season acceptance to browsers, the presence and absence of physical deterrents and foliage retention period into the dry season. Ungulate densities were determined during the late dry season of 1999 by helicopter census. The leaf dry mass production below a height of 2 m, the mean browsing height of kudu, ranged from 362 kg ha' to 695 kg ha' (mean = 516 kg ha') between study units. The forb standing crop (dry mass) ranged from 83 kg ha' to 376 kg ha' (mean = 214 kg ha') between study units. Large-scale kudu mortalities were reported in the dry season of 1998 in the study area. Below average rainfall received during the preceding rainfall season probably contributed to these mortalities, which were further aggravated by a prolonged cold spell experienced at the time. The lack of late dry season woody foliage was significantly related to mortalities. Relationships between kudu mortalities and kudu density or study unit size were insignificant. Kudu faecal nitrogen concentration was determined at regular time intervals during the dry season of 1999. This was preceded by a normal rainfall season. Kudu faecal nitrogen concentration declined during the dry season and reached a minimum during the dry hot season (August - October). Kudu faecal nitrogen concentration peaked during the month of November. Mortalities and poor physical condition of kudu populations were linked to low dry hot season kudu faecal nitrogen concentrations. Variation in kudu faecal nitrogen concentration was significantly explained by the availability of woody species' foliage, excluding the contribution of early deciduous species. It is hypothesised that kudu survival is largely dependent on the nutritional status of the animals. Animals with a low nutritional status are more susceptible to diseases and the effect of physical exposure during adverse weather. The nutritional status of kudu populations is apparently dependent on the availability of dry season foliage resources, which is again dependent on the preceding rainy season's rainfall. During droughts, forage resources available during the late dry season, the critical period, are important. During average rainfall years, kudu appear to be less dependent on critical resources, and the availability of dry season resources before the critical period is entered becomes increasingly important. Different strategies to optimise kudu production, given the variation in forage resources between years, are discussed. It is proposed that kudu carrying capacity in semi-arid savanna is based on the availability of forage resources during the dry season, taking into account the effect of rainfall on resource availability/quality.Item Open Access Supplemental degradable protein sources for beef cattle consuming low quality roughage(University of the Free State, 2005-05) Jacobs, Henry Lubbe; Van der Merwe, H. J.; De Brouwer, C. H. M.; Spangenberg, H. P.English: A study was conducted to determine the best natural source of rumen degradable protein (RDP) not provided by urea to maximize the digestible organic matter intake (DOMI) of a SA natural winter pasture hay (3.51% crude protein (CP) and 74, 23% neutral detergent fibre (NDF). The crude protein degradability of natural winter pasture hay (Cymbopogon- Themeda), cotton oilcake, soybean oilcake and sunflower oilcake was determined by means of the in- sacco- technique. These crude protein degradability values were used to formulate three RDP supplements according to current recommendations (4.01g RDP/kg W 0.75) using the three oilcakes respectively. Urea provided 50% of the supplemental RDP. The other feed ingredients were salt, begasse, molasses, feed grade sulphur and trace minerals. Seven steers (217 SD ± 9.91 kg) per treatment randomly divided were used. The experimental period consist of 14 -day's adaptation, 21- days' intake and 7 days collection period (conventional digestibility study). A significant (P< 0.0001) higher apparent digestibility of NDF occurred when the sunflower oilcake supplement was fed to the steers. The apparent digestibility of dry matter (DM), organic matter (OM), CP and gross energy (GE) was however not influenced significantly (P> 0.05) when different oilcakes supplements were fed. Likewise DOMI/kg W 0.75 , rumen volatile fatty acid concentration and rumen pH did not differ significantly (P> 0.05). The ammonia nitrogen (NH3N) concentration of the rumen fluid of steers that consumed the sunflower oilcake supplements were significantly (P< 0.04) lower than that of cotton oilcake. In a second study the optimum ratio of supplemented urea to the most available oilcake (cotton seed) was investigated. Urea replaced: 0%, 25%, 50%, 75% and 100% of the natural supplemental RDP. The same procedure as described in the first study was used. Steers with an average mass of 200 ± 19.96 kg were used. The replacement of natural supplemental RDP with urea did not significantly (P>0.05) influenced the apparent digestibility of DM, CP, NDF and GE. Accordingly DOMI/kg W 0.75did not differ significantly (P>0.05). The highest (P< 0.05) acetate and propionate concentration in rumen fluid of steers was recorded when urea replaced 75% of the natural RDP in the supplement. The highest (P= 0.008) value for isovalerate concentration in rumen fluid was found when 25% of the supplemental degradable protein was from urea. Increasing levels of urea had no affect on either the rumen NH3N concentration (P=0.3508) or pH (P= 0.0810). According to the results of both studies it seems that urea can supply all the supplemental RDP to steers on low quality roughage. From the results it was concluded that further research is needed on the RDP-requirements of ruminants consuming different types of low quality roughages.Item Open Access The influence of tree thinning and subhabitat differentiation on the reproductive dynamics of acacia mellifera subsp. detinens(University of the Free State, 2001-11) Hagos, Mesghena Ghilay; Smit, G. N.The study was conducted in an area described as "Kalahari Thomveld" in the vicinity of the towns of Bray and Pomfret in the North-West Province, where Acacia mel/itera subsp. detinens is the dominant woody species. The soils of the area are deep sand to loamy soils described as Kalahari sand with an extremely low organic matter and mineral element content. The study area consisted six 0.5 ha plots (50 m x 100 m), where the trees were thinned during November 1989 to different densities, ranging from a totally cleared plot (0%) to plots thinned to the equivalent of 10%, 20%, 30%, and 50% of the tree density of a control plot (100%) of about 2 000 tree equivalents (TE) ha-l. The plots were located adjacently on a homogeneous area of 3.0 ha. Treatments were allocated randomly to the plots and not in numerical order. A permanent transect of 20 m x 100 m was established in the center of each plot for phenological observations and harvesting of seeds. The remainders of the experimental plots were used for soil sample collection and to determine seed distribution within the defined subhabitats. The spatial canopies of all rooted live A. mel/itera trees encountered in the fixed transects (5 m x 100 m), located in the middle of each of the experimental plots, were measured and the number of Evapotranspiration Tree Equivalents (ETTE) ha-l calculated, using the BECVOLmodel. Estimates of the browsing capacities were also made from the leaf dry matter estimates. For the study of the phenology, seed harvesting and leaf biomass estimates of individual trees, fifty (50) A. mel/itera trees (10 sample trees/plot) were randomly selected. Only one phenological observation was done at the onset of flowering (August 2000) and all the pods and seed from the marked trees were harvested during late November 2000. Tree thinning brought about ear1yflowering of A. mel/itera in the lower tree density plots, possibly as a result of reduced inter-tree competition. However, the mean seed production over the tree density gradient did not follow a specific trend, and differences were observed between the seed production of individual trees. Significant correlations between ETTE ha" and leaf dry mass (kg ha") and total seed production ha" were established. Although the correlation coefficients were low, there are indications that seed production of individual trees increase with an increase in ETTE tree-land leaf dry mass tree". For the determination of seed mass and seed dimensions ripe A. mellifera seeds were randomly selected from each sample tree (n = 10 and 50, respectively) after which they were weighed and measured. Seeds harvested from the high tree density plot were longer, wider and thicker than those from the lower tree density plots. The average seed dry mass production tree-1 showed no distinct pattern and was not correlated with the tree density, but the total seed dry mass ha-l increased in relation to an increase in tree density. Leaf biomass of the A. mellifera trees per unit area, expressed as ETTE ha" and leaf dry mass ha", was highly correlated with the seed dry mass ha-l . There is no carry over of A. mellifera seed from one season to another and thus no persisting seed bank exists. The percentage of viable fresh A. mellifera seeds was observed to decrease with the increase of the time and exposure to high temperature and moisture fluctuations. For the study of seed distribution within defined subhabitats (stem base area, under canopy spread and open area), six A. mellifera trees in each tree density plot were randomly selected. Small rectangular plastic containers were inserted. in the three subhabitats of all marked trees (in two opposing directions). In all subhabitats a larger number of seeds were blown toward the prevailing wind direction. The number of seeds accumulated in the open subhabitats in both wind directions was also higher in comparison to the canopied subhabitats. A very low, non-significant correlation was observed between ETTE ha-l and seed distribution along the tree density gradient of the three subhabitats. For the assessment of germination potential, 50 normal and 20 bruchid beetle infested seeds were randomly selected from each plot. Germination tests were conducted at the facilities of the Department of Agronomy, UFS, and root and coleoptile lengths and growth rates were also measured. Thinning of A. mellifera trees had no effect on the germination potential of the seeds from the various tree density plots and an extremely high germination potential of the fresh A. mellifera seeds were found. Though some damage was caused, bruchid beetle infested seeds exhibited a low but fast germination rate, possibly due to faster imbibition of moisture. No marked difference in root length and root growth rates were observed between seeds of the various plots. However, seeds harvested from the lower tree density plots developed a higher coleoptile length with a faster coleoptile growth rate than the control (100%) plot. Soil from the canopied and uncanopied subhabitats were analyzed for soil nutrient status in order to evaluate seedling growth. Soils excavated from the canopied subhabitats were more acidic and displayed higher concentrations of P, total Nand organic matter than the uncanopied (open) subhabitat. However, no marked differences in exchangeable cautions were demonstrated between the subhabitats, except Ca that displayed higher concentrations in the canopied subhabitat. No allelopathic effect that inhibits the growth of seedlings was found to be present in soil from the canopied subhabitats of A. mellifera. Marked differences in growth parameters of the seedlings grown in the soils from around the stem base area in comparison to the other two subhabitats were observed. The relatively higher soil nutrient status observed in soils of this subhabitats is considered responsible for this increased growth. In general, A. mellifera seedlings grown in the soil from the lower tree density plots exhibited higher growth rates than those from the control (100%) plot. A denser root system, as reflected by higher total root lengths and root dry mass, was observed in seedlings grown in soil from the low tree density plot and declined linearly in soils collected along the tree density gradient. In general, the subhabitat differentiation had a more pronounced effect on seedling growth than soil differences associated with the tree density gradient.Item Open Access The use of different anabolic agents in gilts(University of the Free State, 1995-07) Dias, Geraldo Paulino; Greyling, J. P. C.; Kotzé, W. F.24 Crossbred gilts (Large White x Landrace) purchased as weaners were randomly allocated to four treatment groups (n = 6) and submitted for an observation period of three phases: Phase I, in which the animals were treated with anabolic agents (nandrolone, clenbuterol, zeranol); Phase 2, could be seen as the anabolic agent clearance period; and Phase 3, in which certain carcass characteristics and meat quality parameters were measured. The trial was aimed to compare the effect of the different anabolic agents zeranol (implants of 36 mg/pig, every three weeks, for 9 weeks), clenbuterol (daily oral dose of 0.5 mg/pig, for 9 weeks) and nandrolone (intramuscularly injected, 50 rng/pig, every ,3 weeks, for a period of 9 weeks), on growth rate parameters, carcass and meat characteristics, visceral organ growth and blood concentrations of urea, glucose, creatinine, oestradiol and the hematocrit. The gilts were individually housed and fed a pig growth diet (16% crude protein) ad libitum, with free access to water. Body weight of all animals were recorded every 48 hours to monitor the average daily gain (ADG) and the growth rate up to the target liveweight of 85 kg. Weekly feed intake was monitored and the feed conversion rate (FCR) determined for the individual animals and the mean of the groups. Backfat thickness (P2) and eye muscle diameter were measured weekly with the aid of a sonar apparatus in all animals, to monitor the deposition of fat and lean muscle. Blood was sampled weekly from 4 specific animals per group for the determination of hematocrit, blood urea, blood glucose, blood creatinine and blood oestradiol concentrations. The clearance rate of the anabolic agents was monitored in the urine sampled every second day from all anabolic agent treated animals following cessation of treatment. At slaughter (85 kg liveweight), several carcass measurements were done. Visceral organ weights were noted and meat quality parameters (water loss, cutting resistance, pH) were determined. Zeranol treatment revealed an improved growth rate (ADG of 727 g/d and 147.3 days to attainment of 85 kg) compared to the control and the other treatment groups. None of the three anabolic agents improved the FCR significantly, although the control showed the lowest mean value (2.76 kg feed/kg liveweight gain). A tenclency for an increase in this parameter was observed over time, in all the groups, the highest mean value being encountered in the group treated with zeranol (3.32 kg feed/kg liveweight gain). Overall average daily feed intake was significantly (P<0.05) greatest in the zeranol treated animals (2.03 kg/cl). Backfat thickness (P2) deposition assessed through ultrasonic measurements, showed no significant differences between the treatments and the control. The diameter of the eye muscle, weekly monitored by the same method, from the P2 site, showed significant (P<0.05) differences - the control having the highest value (4.43 mm/week). The clearance rate of the anabolic agents was faster in clenbuterol treated animals than in the zeranol group, while for nandrolone group this could not be. assessed, because its metabolites in swine are still unknown. Zeranol treated animals had a significantly (P<0.05) improved cold carcass weight and dressing percentage (68.8 kg and 79.8% respectively). Mean values for backfat thickness were generally high in carcasses from zeranol treated animals (PI = 13.5 mm; Pi = 14.8 mm; P3 = 16.6 mm) which leaner carcasses were obtained in the clenbuterol group (PI = 6.7 m; P2 = 7.4 mm; P3 = 8.6 mm). The eye muscle area (physically measured) was significantly (P<0.05) higher in the nandrolone group (34.3 cm2) compared to the Zeranol group (30.6 cm2), but not statistically different from the control and the nandrolone group. Zeranol, clenbuterol and nandrolone treatments did not significantly alter carcass conformation indicators. However, carcass weight was recorded to be positively (P< 0.05) correlated to ham circumference (r = 0.52); chest depth (r = 0.64) and chest diameter (r = 0.56). With the exception of cutting resistance values, in which the zeranol treatment group produced more tender meat (3.74 kg shear force) than the control and the other two treatments, the rest of meat quality parameters measured (muscle pH; cooking loss of water holding capacity) were not affected by the treatment with anabolic agents. No significant differences in the weights of digesta, digestive tract and the visceral organs (liver, kidneys, lungs, heart and spleen) were found following anabolic agent treatment. Suppressed ovary growth (0.6 g of weight) and over-growth of the reproductive tract (134 g uterus weight) and increased size of the vulvas were observed following zeranol implantation of gilts. The reproductive organs from clenbuterol and nandrolone groups were functional and apparently unaffected. The determination of blood urea, blood glucose, blood creatinine and blood oestradiol levels using specific kits to assess the concentrations of the metabolites and hormones generally did not result in definite trends of increases or decreases over time. These determinations could thus not be accurately used as possible indicators of the metabolic status following the use of zeranol, clenbuterol and nandrolone in gilts. It was concluded that the use of clenbuterol and nandrolone in gilts yielded no improvements in the growth parameters. In gilts treated with zeranol, overall growth rate was higher. Ultrasonic measurements of backfat thickness and eye muscle diameter proved to be an inaccurate and unreliable predictor of fat thickness or leanness of the carcass. A longer withdrawal period is necessary after an implantation of pigs with zeranol compared to the rapid clearance realised after an oral dose of clenbuterol. The faster growth rate obtained following the use of zeranol implants is counteracted by higher feed costs of lean meat production and the yield of poorer ratio of lean-to-fat content in the carcass when compared to the clenbuterol and nandrolone treatments. The growth of the digestive tract, liver, heart, kidneys, spleen and lungs were not affected by anabolic agent treatment, and thus the anabolic effect of zeranol concerning growth characteristics is not through an increased gastrointestinal capacity. The assessment of growth performance and feed utilisation efficiency through blood levels of glucose and urea appear to be time consuming and not always practical. Further investigations regarding blood biochemistry, ideal doses of the anabolic agents, their metabolism and clearance rate in swine, as well as the margin of consumer's safety, is still of crucial importance for the future legal and safe use of anabolic agents in the pig industry. From the results obtained, it would seem that the use of these anabolic agents for the respective treatment periods and doses in gilts are not justified.Item Open Access Evaluation of cryopreservation methods for in vitro produced bovine embryos(University of the Free State, 1999-11) Nedambale, Tshimangadzo Lucky; Greyling, J. P. C.; Rust, J. M.English: The objective of this study was to evaluate four cryopreservation techniques for in vitro produced bovine embryos, and to select the best method for practical application. The cryopreservation methods investigated were three vitrification methods and a slow freezing method. This study was done at the ARC-Animal Improvernent Institute in conjunction with the University of the Orange Free State (Department of Animal Science). Embryos were obtained by the IVM, IVF and IVC of bovine follicular oocytes. A total of 136 early blastocysts, blastocysts and expanded blastocysts were randomly assigned to four different treatment groups. In the conventional slow freezing method, the IVP bovine embryos were first held in ViGro™Holdingplus medium before being transferred to 1.5M ViGro™EG Freezeplus medium (TMT 4). In this technique, the IVP embryos were loaded into 0.25ml straws. The straws containing the embryos were immediately placed into a programmable freezer (CL-863 cryo-chamber) at -6°C. Straws were seeded after a 5 minutes equilibration period. Embryos were initially cooled from -6 "C to -30°C at a rate of 0.3 °C/min. Thereafter, from -30°C to -33°C the rate was changed to 0.1 °C/min. After the target temperature was reached, straws were immediately transferred to liquid nitrogen. Vitrification of IVP bovine embryos was performed according to the following procedures: Embryos were initially placed in 10% EO in ViGro™Holdingplus medium for 5 minutes (Equilibration I), thereafter in 40% EO + 0.3M trehalose in ViOro ™Holdingplus medium for 5 minutes (Equilibration 11), both at room temperature. Embryos were then transferred to vitrification solutions, containing 40% EO (TMT 1); 40% EG + 0.3M trehalose (TMT 2); 40% EG + 0.3M trehalose + 20% PVP (TMT 3) in ViGro TM Holdingplus. Embryos were then loaded into 0.25ml straws, and plunged directly into liquid nitrogen (LN2). The straws were vertically stored in liquid nitrogen (- 196°C) until thawing and evaluation took place. Thawing of embryos within the straws was carried out in a water bath (32 DC). Each straw was placed in a water bath for 30 seconds. The straws were dried, cut and the contents transferred to ViGro ™Holdingplus medium. Recovered embryos were washed twice in fresh ViGro™I-Ioldingplus, and embryos were morphological examined for their viability under a stereo microscope. The viable embryos were cultured in IVC media. Embryo survival was recorded immediately after thawing, 24 hours and 48 hours post-thawing by monitoring the re-expansion of the blastocoel and expansion of the blastocyst. Statistically, there was a significant (P<0.05) difference in survival rate between embryos frozen in TMT 3 (77%), compared to those frozen in TMT 2 (41%), immediately after thawing. There was no significant difference in embryo survival rate for the other treatment groups. At 24 hours post-thawing, there was a significant (P<0.05) difference in survival rate between embryos frozen in TMT 3 (60%), compared to those frozen in TMT 1 (26%). There was also a significant (P<0.05) higher survival rate for embryos frozen in TMT 3 (60%), compared to those frozen in TMT 2 (21%). At 48 hours post-thawing, however, there was no significant difference in survival rate for embryos frozen in all the treatment groups. TMT 3 had the highest survival rates of embryos (37%). The generalized linear model (Bonferroni multiple comparison test) was used to test and predict the embryo survival rate between the treatment groups. The predicted (theoretical) embryo survival rate correlated highly and significantly (P<0.05) higher with the survival rate of embryos frozen in TMT 3. Embryos Frozen in TMT 3 were also predicted to be more likely to survive, compared to the other treatment groups. The results clearly indicate the beneficiary effect of this vitrification method (TMT 3). Vitrification is simple and more cost effective, compared to the slow freezing method (TMT 4), which is time consuming and expensive. Although there was no significant difference 48 hours ostthawing, TMT 3 could be recommended as the method for cryopreservation of IVP bovine embryos. The addition of 0.3M trehalose with 40% EO in the ViGro™Holdingplus medium decreased the survival rates of the IVP bovine embryos. Embryos frozen and thawed in 40% EO in ViGro™Holdingplus had higher survival rates, compared to those frozen/thawed in TMT 2, from immediately after thawing, to 48 hours post-thawing. Perhaps the addition of trehalose in the solution (ViGro™Holdingplus), already containing non-permeating agent (sucrose), increased the concentration of non-permeating agent in the freezing solution. High concentrations of non-permeating agent may be detrimental or toxic to the embryos. The presence of 20% PVP with 0.3M trehalose and 40% EO dramatically increased the survival rate of IVP bovine embryos. The PVP plays some kind of protective role during the freezing and thawing processes. Although the mechanism of protection is not clear, it may be that it prevents water from entering the cells during vitrification and thawing, which in turn prevents intracellular ice formation. Intracellular ice formation is lethal to embryos during thawing. It can be concluded that the combination of 40 % EO + 0.3M trehalose + 20% pyp (TMT 3), used as a vitrification solution, be recommended as suitable method for cryopreservation of IVP bovine embryos. It gave the highest embryo survival rate from immediately after thawing to 48 hours post-thawing. The advantage of this vitrification technique is that it is simple, quick and inexpensive. Additional research is needed to develop an effective cryopreservation method that will reduce the sensitivity problem of in vitro produced embryos. In vitro produced embryos contain lipids that cause them to be more sensitive to freezing, compared to those produced in vivo. The ability of vitrified in vitro produced bovine embryos still needs to be evaluated for their development in utero, in controlled embryo transfer programs.Item Open Access Die invloed van die frekwensie van kragvoervoeding op die benutting van melkbeesrantsoene(University of the Free State, 1989-01) Matthee, Stephanus Willem; Van der Merwe, H. J.; Engels, E. A. N.Afrikaans: In die geval van hoë produserende melkbeeste word groot hoeveelhede kragvoer, by twee geleenthede per dag aan melkkoeie verskaf. Hierdie praktyk mag moontlik met 'n lae rumen-pH na kragvoervoeding, verskuiwings in die rumenmikrobepopulasies, veranderings in eindprodukte van vertering en swakker rantsoenbenutting gepaard gaan. Na aanleiding hiervan is ondersoek ingestel na die invloed van frekwente kragvoervoeding op rantsoenverteerbaarheid, rumenparameters, voerinname, liggaamsveranderings en produksieparameters. Twaalf volwasse Frieskoeie is in twee produksiegroepe (HP-hoë produksie en LP-laer produksie) gestratifiseer. Volgens melkproduksie is kragvoer in twee-, vier- of agt porsies per 24-uur verskaf. Bykomstig is grof gemaalde (25 mm) lusernhooi ad lib. aan proefdiere verskaf. Hierdie prosedure is gedurende vroeë, mid- en laatlaktasie in 'n gebalanseerde omskakelingsproefontwerp uitgevoer. Binne elke laktasiestadium is drie verterings- en innamestudies uitgevoer, waartydens rumenparameters by gefistuleerde koeie (die helfte van die proefkoeie in elke produksiegroep) ook bestudeer is. In teenstelling met LP-koeie het frekwente kragvoervoeding met 'n nie-betekenisvolle (P ≤ 0,05) verhoging in die skynbare verteerbaarheid van droë- en organiese materiaal, ruproteïen en veral vesel by HP-koeie (23,9 kg melk/dag) gepaard gaan. Hierdie geringe verhogings het ten spyte van laer kragvoerkonsentrasie en geringe hoër DM-inname tydens die verteringsproewe voorgekom. Frekwente kragvoervoeding het geen statisties betekenisvolle effek op die gemiddelde daaglikse rumen-pH, variasie in pH oor 24-uur periodes, minimum pH-waardes, tydsduur van pH verlagings, ammoniakkonsentrasie, totale en individuele vetsuurkonsentrasie en asyn- tot propioonsuurverhouding in die rumen uitgeoefen nie. Neigings tot In laer gemiddelde rumen pH (by HP-diere - waarskynlik weens hoër voerinnames) en meer konstante rumen-pH het met frekwente kragvoervoeding voorgekom. Alle proefkoeie het, veral gedurende vroeë- en midlaktasie (30,98 tot 57,40% kragvoerrantsoene) laer rumen pH's getoon. Eweneens het frekwente kragvoervoeding slegs geneig om 'n laer gemiddelde daaglikse ammoniakkonsentrasie te veroorsaak. Tendense soos 'n meer konstante rumenammoniakkonsentrasie en laer ammoniakpieke na kragvoervoeding is in sommige gevalle met frekwente kragvoervoeding gevind. Beide asyn- en propioonsuurproduksie het oor die algemeen 'n geringe styging met frekwente kragvoervoeding getoon. In sommige gevalle is ook nie-betekenisvolle kleiner variasie in totale en individuele vlugtige vetsure en As: Ps-verhouding rondom die daaglikse gemiddeld vanweë frekwente kragvoervoeding waargeneem. In ooreenstemming met verteerbaarheid en rumenparameters het frekwente kragvoervoeding geen statistiese betekenisvolle (P ≤ 0,05) voordeel ten opsigte van die inname van voer- en verteerbare voedingstofinname gelewer nie. 'n Neiging tot verhoogde ruvoerinname, deurdat fisiese en metaboliese innamebeperkings moontlik in In mate opgehef is, het veral by die frekwent gevoerde HP-diere (30 tot 57% kragvoer) voorgekom. 'n Soortgelyke neiging tot verhoogde inname van voedingsbestanddele (DM, OM, RP en NDF) en verteerbare voedingstowwe is by die frekwent gevoerde diere waargeneem. Geen statisties betekenisvolle (p ≤ 0,05) verskille in liggaamsmassaveranderings, melkproduksie en -samestelling (bottervet, proteïen en laktose) het voorgekom nie. Frekwente kragvoervoeding het slegs met 'n geringe verhoging in melkproduksie by die HP-diere gepaard gegaan. Relatief lae bottervetkonsentrasies, waarskynlik weens algemene hoë voerinnames en lae rumen-pH's, het gedurende vroeë- en midlaktasie voorgekom. Verder het frekwent gevoerde diere in die huidige studie geen voordeel bo konvensioneel gevoerde diere in die doeltreffendheid van voer- en ME-benutting vir melkproduksie getoon nie. Samevattend blyk dit volgens die resultate van die huidige ondersoek dat frekwente kragvoervoeding by melkbeeste, inname, rumenomgewing , vcedingstofbenutting en melkproduksie en kwaliteit nie noemenswaardig beïnvloed nie. Hierdie bevindinge geld egter slegs vir die kragvoerpeile (maksimum 57%) wat in die huidige studie toegepas is.