Animal, Wildlife and Grassland Sciences

Permanent URI for this community

http://hdl.handle.net/11660/91

Browse

Now showing 1 - 20 of 105

Open Access
Alternative management systems to increase beef production under extensive conditions
(University of the Free State, 2016-06) Grobler, Susanna Maria; Scholtz, M. M.; Greyling, J. P. C.; Neser, F. W. C.
South Africa is still a net importer of beef. Therefore, by increasing off take in the beef sector, South Africa can move towards self-sufficiency. With fertility being regarded as one of the main components influencing total beef herd efficiency, it is essential that the quoted calving percentage of 62% in the commercial beef sector of South Africa must be improved. If the long calving seasons can be shortened and the calving percentage increased, more and heavier calves with a more uniform age can be weaned. Cows that calve early also have a better chance of conceiving in the next breeding season and are generally seen as the more fertile animals Development, production and quality of replacement heifers is a crucial component in the extensive beef production system. In general, beef heifers are managed to calve for the first time at three years of age, but in some cases mating of heifers at one year of age have been advocated. All extensive beef production systems in South Africa are dependent on natural veld and it is well documented that veld condition have a huge influence on a number of beef production parameters. Studies conducted on natural veld have concentrated mainly on aspects that affect herd efficiency, including calving percentage, pre-weaning growth and supplementation of cows and calves. However, none of the studies focused on the reproduction performance of beef cattle mated naturally after synchronization, heifer age at breeding and effect of grazing system on veld condition. The aim of the study was to evaluate: the effect of estrous synchronization followed by natural mating on the calving percentage and calving distribution of multiparous beef cows and heifers; effect of breeding heifers at either 14 months or 26 months of age and the evaluation of a high utilized grazing system and controlled selective grazing on veld condition and animal performance. The effects of climate on cow-calf production characteristics over time was also evaluated. The study was conducted from 2009 to 2015 at the Roodeplaat experimental farm (REF) of the ARC-Animal Production Institute (25°34’11.27’’S; 28°22’05.36’’E) on 900 ha of natural rangeland described as Sourish Mixed Bushveld. The experimental herd (n=92) was divided in four sub-herds consisting of 23 cows each at the beginning of the project in 2009. It was ensured that the four sub-herds were as uniform as possible at the beginning of the project e.g. age, weight, previous number of calves. Within each sub-herd, 50% of the cows and heifers were synchronized prior to the commencement of the breeding season. Two sub-herds were subjected to high utilized grazing and two sub-herds were subjected to controlled selective grazing. The two grazing systems were related to the use of 30% or 60% of the available grass dry matter. Half the heifers were mated at 14 months and the other half at 26 months. Results from this study indicated that calving percentage and body condition score did not differ significantly (P=0.54) between cows that was either synchronized or not synchronized followed by natural mating. However, estrous synchronization prior to natural mating did influence the average days to conception with synchronized cows calving earlier, except for 2012 in the calving season. Over the six-year project period 15% more cows from the synchronized group conceived within 293 days after the onset of the breeding season. Calves from the synchronized cows weaned on average 5kg heavier than the cows that were not synchronized although this difference was not significant. Conception rates of heifers mated at 26 months were significantly (P<0.05) higher than heifers mated at 14 months of age. It would seem that it may be more viable to breed Bonsmara heifers in an extensive production system in the Sourish Mixed Bushveld region at 26 months of age for the first time. Synchronization of 14 month old heifers did not improve conception rate over 14 month old heifers bred naturally. However, the calving percentage of synchronized heifers bred at 26 months was 6% higher than the non-synchronized heifers. Almost no veld condition change was recorded except for veld condition scores for both controlled selective grazing and high utilization grazing. In addition, the results indicate a tendency that high utilization grazing improved veld condition score and grass species composition over that of controlled selective grazing, but the duration of the study is too short to make a definite conclusion on the effect of grazing strategy on veld condition. It was also shown that grazing strategy did not have a significant influence on cow weight and calf growth over the six-year period, indicating that both grazing strategies are sustainable in the Sourish Mixed Bushveld if carrying capacity is adhered to. With the significant differences between years (P ≤ 0.05) for calving percentage, cow weight at calving, cow weight at weaning, calf birth weight, calf weaning weight and body condition score over the six-year observation period, the effect of seasonal temperature, relative humidity and rainfall is elucidated. Forward stepwise regression procedures were performed to determine what climatic data were involved in cow and calf weight at birth and weaning as well as calving percentage. In spite of the high standard errors (which were probably due to the small sample size), maximum relative humidity one month prior to the start of the breeding season, made a major contribution to explain calving percentage and minimum temperature within the last month of the 3 month breeding season, had a low negative correlation with calving percentage. It can be speculated that high humidity in the study region (Sourish Mixed Bushveld) is an indication of warm and wet conditions, negatively impacting cow and bull comfort, leading to lower conception rates. The negative correlation between minimum temperature within the last month of the breeding season and calving percentage may indicate that the cows were unable to cool down at night during the warmer summer months of the year, leading to lower conception rates and resorptions. The researcher acknowledge that the available herd size may be a limitation and that a bigger herd or sub-herds’ size combined with bigger land size could benefit the project outcome, possibly resulting in more significant differences and/or enhanced interpretation of results.
Open Access
Animal performance and utilization of opuntia-based diets by sheep
(University of the Free State, 2008-05) Einkamerer, Ockert Bernard; de Waal, H. O.
English: Incremental levels of sun-dried and coarsely ground cactus pear (Opuntia ficus-indica var.Algerian) cladodes were used to substitute part of the lucerne hay in balanced diets and fed to 28 Dorper wethers. The extent to which sun-dried and coarsely ground Opuntia cladodes can be incorporated in balanced sheep diets without effecting sheep performance was investigated over a period of 70 days. The three treatment diets (T0, T24 and T36) used in this study comprised respectively (air-dry basis) 0, 240 and 360 g/kg sun-dried, coarsely ground Opuntia; 660, 410 and 285 g/kg coarsely ground lucerne hay; 300 g/kg yellow maize meal; 0, 10 and 15 g/kg feed grade urea; and 40 g/kg molasses meal. The dry matter intake (DMI) varied little between diets but the apparent digestibility increased [P<0.05; 71.4% (T0) vs. 75.6% (T36)]. The average daily gain (ADG) of the wethers decreased slightly as Opuntia inclusion increased. This suggests that the overall effects of the diets on the performance of the wethers were small. As the inclusion level of Opuntia increased in the diets, the water intake of the wethers also increased (P<0.05; T0 vs. T36), while urine excretion showed little increase (P>0.05). The faeces DM excreted remained the same for all diets, but with the higher levels of Opuntia inclusion the DM content of the faeces excreted visibly decreased considerably. It is suggested that the mucilage ingested via the Opuntia and present in the digestive tract of the wethers may have interacted with the water fraction in the digesta, rendering some of the water unavailable for absorption. Hence, the wethers were compelled to drink more water to compensate for this extra water loss via the faeces. The wetter faeces were assumed to be the result of diarrhoea by some researchers, but the wet faeces lacked the customary foul smell associated with diarrhoea. Opuntia inclusion in the diets had no effect on carcass characteristics of the wethers (weight, fat thickness, surface area of musculus longissimus dorsi and relative tissue coefficients). This suggests that the effect of Opuntia in the treatment diets on the carcass weight and quality of the wethers were small. From these results, it seems that, irrespective of the dietary treatment, adequate nutrients for sheep maintenance and production was supplied by the diets. Sun-dried and ground Opuntia cladodes can be seen as an alternative feed supplement in semi-arid and arid regions of most countries that can be included in sheep maintenance or production diets without any detrimental effects on animal performance or carcass quality. It is recommended that research should focus on the formulation of Opuntia-based production diets with a high energy content, to be used in feedlots. The effect of mucilage on the wetter faeces excreted by sheep 61 on Opuntia-based diets and what happens in the alimentary canal also needs further investigation.
Open Access
Anthropogenic influences on distance traveled and vigilance behavior and stress-related endocrine correlates in free-roaming giraffes
(MDPI, 2021) Scheijen, Ciska P. J.; Van der Merwe, Sean; Ganswindt, Andre; Deacon, Francois
Giraffes are an important tourist attraction, and human presence to wildlife is increasing. This has an impact on an animal’s behavior and its endocrine correlates. Studies on other species show alterations in movement patterns, vigilance, and stress-related hormone levels in the presence of humans. Limited information is available on how anthropogenic activities alter giraffe’s behavior, social structure, and related endocrine parameters. The purpose of this study was to obtain insight into anthropogenic influences on giraffe’s behavior and adrenal activity. We used GPS devices mounted onto giraffes to compare the distance walked in the presence or absence of human observers. We also conducted behavioral observations to assess their vigilance and collected fecal samples to analyze their fecal glucocorticoid metabolite (fGCM) concentrations. Giraffes walked significantly further distances in the presence of humans, but the cumulative time that observers were present decreased the hourly distance walked with an observer present, suggesting that the giraffes were becoming habituated. The number of observers present significantly increased the percentage of time spent on observing an observer as well as the number of unhabituated individuals present in the herd. The percentage of time spent observing a human observer did not decrease with the increase of habituation. Last, fGCM concentrations increased with human presence but decreased when individuals became habituated to human presence. More research is needed to understand the effect of anthropogenic influences in different scenarios (e.g., tourism, vehicles, hunting, etc.).
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.
Open Access
Causes and consequences of fenceline contrasts in Namibian rangeland
(University of the Free State, 2011-02-15) Zimmermann, Ibo; Smit, G. N.
English: This study made use of the opportunity provided by fenceline contrasts in Namibia to measure differences in rangeland and learn from farmers about the inputs and outputs of management on each side of the fence. The 34 measured contrasts were mostly clustered within the Camelthorn and Thornbush Savannas, with three in the Highland and Dwarf shrub Savannas of Namibia. Mean annual rainfall ranges from 235 to 475 mm. Rangeland measurements focussed on well established perennial vegetation to avoid the fluctuating effect of ephemerals. Eight characteristics were measured and significant (P<0.05) differences occurred in at least one of these at each contrast. Two characteristics (distance from sample point to the nearest perennial grass and the species) were combined to determine a rangeland condition index. At 22 of the 34 contrasts the condition index was significantly (P<0.05) higher on one side of the fence. There was no clear method to distinguish between the influences of different management inputs that may have caused the fenceline contrasts. Therefore, subjective judgment was relied upon to identify bush control as the most likely single causative factor at ten contrasts, stocking rate and period of rest at five contrasts each, and stocking density at two contrasts. Management contributed to both causes and consequences of fenceline contrasts. The negative correlation between stocking rate and rangeland condition index was weak (r = −0.2575, P = 0.04, n = 64), suggesting that there may have been more farms where a higher stocking rate was the cause of poorer rangeland than farms where the higher stocking rate was the consequence of better rangeland raising the carrying capacity. The stronger correlation between profit and income (r = 0.9288, P < 0.001, n = 25) than between profit and expenditure (r = 0.0267, P = 0.899, n = 25), suggests that farmers should focus on reducing non-essential expenditure to increase profitability. Game farming can earn high income, but continuous selective grazing by gregarious game animals may lead to poorer rangeland condition. Useful lessons were learnt from the case study of an innovative farmer who adapted his management based upon his keen observations of rangeland dynamics. Many of his interventions were strategically timed in relation to rainfall events. There is much that can be learnt by both scientists and other farmers from the management strategies applied by successful farmers who earn a good profit while sustaining the rangeland.
Open Access
Characterization and cryopreservation of semen of four South African chicken breeds
(University of the Free State, 2009-11) Mosenene, Thatohatsi Madaniel Bernice; Greyling, J. P. C.; Schwalbach, L. M. J.
The aim of the study was to characterize and evaluate the quality of fresh semen of 4 breeds of chicken and the susceptibility of cockerel semen to a cryopreservation protocol, assessed microscopically for sperm motility and morphology and ultimately fertilizing ability following AI. The differences between breeds were determined by comparing the fertilizing ability and hatchability of fresh and frozen-thawed semen. The study was carried out at Glen Agricultural Development Institute and at the University of the Free State. Four chicken breeds, namely the Rhode Island Red, Potchefstroom Koekoek, New Hampshire and White Leghorn, were used. Qualitative characterization of the semen was performed in 28 cockerels (7 per breed). Semen was collected using the massage technique twice a week in the first trial. The eosin-nigrosin staining technique was used to microscopically evaluate the morphology of the sperm from the different breeds. The fresh semen parameters evaluated were ejaculate volume, semen colour, semen pH, sperm concentration, the percentage live and dead sperm, sperm motility and the abnormalities of the sperm. The percentage live and dead sperm, sperm motility and abnormalities were also evaluated for the frozen-thawed cockerel semen. During the second phase of the study, semen was collected 3 times per week from the same cockerels. Semen was frozen using a fast–freezing procedure on dry ice, with 10% DMSO as the cryoprotectant. AI was performed on 4 different breeds of hens (20 hens per breed) (Rhode Island Red, Potchefstroom Koekoek, New Hampshire and White Leghorn), using fresh semen (control) and frozen-thawed semen. During AI of each breed, 10 hens were inseminated with fresh and the remaining 10 hens with frozen-thawed semen. The sperm characteristics of the semen samples of the 4 breeds recorded were ejaculate volume, ranging from 0.3±0.1 to 0.4±0.1ml, semen pH of 7.6±0.4 to 7.7±0.3, sperm motility (scale of 0-5) 2.8±0.8 to 3.1±0.9, estimated sperm motility 58.8±12.5 to 63.8±13.6%, ejaculate concentration (x109 sperm/ml) of 320.4±286.5 to 748.5±475.3, percentage live sperm 75.6±29.1 to 81.5±26.8%, and the percentage dead sperm 18.6±26.8 to 24.4±29.1% respectively, with the percentage normal sperm ranging between 77.3±17.1 and 84.8±9.0%. Head, mid-piece, tail and other sperm abnormalities of the fresh semen of the 4 breeds ranged from 2.9±3.3 to 7.7±9.6%, 7.9±5.2 to 11.0±7.0%, 0.4±0.8 to 1.9±3.0% and 0.6±0.9 to 1.5±1.9%, respectively. Semen samples were frozen in pellet form on a block of dry ice, by pipetting into the indentations on the surface of the ice. The frozen cockerel pellets were thawed following cryopreservation, by being placed into a test tube in a water bath (60°C), and the tube shaken continuously until complete thawing of the pellet. During the time of semen cryopreservation, a decrease in the number of live, morphologically normal sperm, and increase in the percentage dead sperm and sperm with abnormalities were recorded. The freeze-thawing process caused a significant (P<0.05) decrease in the percentage live sperm and the sperm motility, ranging between 37.4±10.4 and 42.3±12.1% and 3.6±0.5 and 3.9±0.3 respectively. A consequent increase in the percentage of dead sperm (between 57.7±12.1 and 62.4±10.8%) was also recorded. The sperm abnormalities regarding sperm head abnormalities ranged between 17.3±3.8 to 22.5±10.3%, the mid-piece abnormalities 7.9±3.8 to 10.4±2.0% and the tail abnormalities between 0.5±0.9 to 2.0±2.4% respectively for the thawed semen. Frozen-thawed semen was thawed in a water-bath 60°C and hens were inseminated twice per week using the frozen-thawed semen, and once a week with fresh semen for a total period of two weeks. Data for the two trials were analyzed using the ANOVA and the Tukey’s Studentized Range (HSD) test for repeated measures (SAS system General Linear Models Procedure). A total of 973 eggs, from all breeds of chicken namely the Rhode Island Red, Potchefstroom Koekoek, New Hampshire and White Leghorn were collected following AI with fresh and frozen semen from individually caged hens. Eggs were collected, incubated and hatched to check if fertile and normal chicks could be produced from frozen-thawed cockerel semen. The difference in fertility and hatchability of the hens of the different breeds were compared and found to be highest in Rhode Island Red, White Leghorn, and Potchefstroom Koekoek respectively and lowest in New Hampshire using fresh semen. When using frozen-thawed semen, the sequence of fertility performance was the White Leghorn, Rhode Island Red, Potchefstroom Koekoek and New Hampshire, respectively. The effect of the numbers of sperm per AI dose on fertility, age at embryonic death, and hatchability of fertile eggs were also evaluated. Low numbers of sperm per AI in the hens resulted in a decrease in the total number of chicks hatched. The lowest fertility rate recorded was in the New Hampshire (2.7%), when using frozen-thawed semen to inseminate the hens. This may be attributed to the low numbers of sperm inseminated per AI dose. Egg hatchability of the fertile eggs was high in the White Leghorn (13.6%), Rhode Island Red (12.8 %), Potchefstroom Koekoek (9.7 %) and low in New Hampshire (2.7%) respectively, which could possibly be attributed to the egg size. Medium sized eggs were preferable for setting, in order to obtain an acceptable hatch, as they generally hatch better than the larger eggs. The results recorded for fertility and hatchability in the control group (fresh semen), was similar to the results recorded by other researchers, showing that the AI method used was acceptable. There still exists a necessity to develop an ideal cryopreservation method (diluent and freezing procedure), which would allow for acceptable long term storage of cockerel semen in liquid nitrogen (-196°C) for future use and export with minimum loss regarding sperm viability and fertilizing capacity.
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.
Open Access
Characterization of breed additive and heterosis effects in beef cattle using experimental results
(University of the Free State, 2011-09) Theunissen, Anette; Scholtz, M. M.; MacNeil, M. D.; Neser, F. W. C.
The objective of this study was to infer direct and maternal additive effects and direct and maternal heterosis effects for growth, fitness and carcass traits in beef cattle using least squares means estimated from crossbreeding studies by Els (1988) and De Bruyn (1991). The dataset was formed by recording each least squares mean along with the breed composition, maternal breed composition and direct and maternal heterozygosity. Each trait was analyzed using a single trait fixed effect model which included source of data as a fixed effect and breed composition and heterozygosity as covariates. Breed solutions were relative to the Afrikaner breed. Heterosis results were also obtained for crosses not made. Among breed groups, crossbred calves showed higher average values for almost all traits than purebred calves. The average direct heterosis contributions to weight traits in ten two-breed genotypes, which involved the Afrikaner (A) as dam line and the Simmentaler (S), Brahman (B), Charolais (C) and Herefords (H) as sire lines were 3.5, 7.9, 8.2 and 4.3% for birth weight (BW), weaning weight (WW), 19-month heifer weight (HW) and cow weight at partus (CW) respectively. Similarly, the average maternal heterosis effects for the weight traits in the four A crossbred dam genotypes (BA, CA, HA and SA) were 1.5, 8.8, 4.9 and 2.9% for the growth traits respectively. Due to additive and non-additive effects of C and B purebreds on BW these sires should only be bred to mature cows. For a weaner calf production system, the C genotype had the highest direct breed effect of +64.1 kg or 34.8% for WW. The combined additive effect of the C dam line was however, exceeded by the S dam line (+38.4 kg or +20.9% versus +50.0 kg or +27.2%). The total combined heterosis effect of the CA dam line was +32.5 kg versus the +19.2 kg effect of the SA dam line. The average expected phenotypic values for WW for the SA dam line was thus larger than the CA dam line (233.3 versus 230.7 kg). The maternal heterosis effect of the HA dam was the second largest (+22.1 kg) of the four two-breed combinations of A. The B genotype used in the study did not have a true superior ability to increase the expected WW in the A breed. The direct and maternal heterosis effects of the breed were - 0.5 kg or -0.3% and +22.1 kg or 12.0% respectively. The H breed had the lowest direct breed effects of +24.7 kg or +13.4% on WW out of the four purebred sire lines that were bred to the A dam line and a small negative direct heterosis effect (-0.5 kg or -0.3%). Furthermore, the maternal additive effect was negative (-29.6 kg or -16.1%). The maternal heterosis effect however, was positive (+22.1 kg or +12.0%). The A sire line had the lowest expected phenotypic values for HW and CW (323.9 and 434.3 kg respectively), indicating that these heifers would probably reach puberty earlier and that these cows would be smaller compared to genotypes from S, B, C and H genotypes. On average two-breed genotypes had 48.9 and 40.6 kg expected increase in HW and CW respectively, and an additional 21.9 kg and 20.4 kg for the two traits respectively in threebreed genotypes (backcrossing excluded). The H sire line did not have a true ability to increase expected CW in the A breed. The C genotypes had the lowest average individual heterosis effect of -17.6 kg (-4.0%) on CW of all four sire lines which were involved in the ten different two-breed combinations of the study. However, the CA dam line was responsible for the highest maternal heterosis effect of +54.8 kg or +12.6% out of the four crossbred A dam lines. By utilizing genotypic differences the opportunity for high productivity and profitability can be maximized, especially through cumulative traits such as the calf/cow weight ratio. All crossbred genotypes, except the BA genotype, increased the calf/cow weight ratio. Results indicated that the A breed should constitute 75% of the genetic make up of B and C crossbred genotypes and 25% of H and S crossbred genotypes to maximize calf/cow weight ratios. The HSA, HBA and BSA, genotypes had the largest calf/cow weight ratios of 0.509, 0.506 and 0.495 respectively, mainly due to the large direct heterosis effects of +22.7 (+12.3%), +28.0 (+15.2%) and +36.7 kg (+19.9%) of the HS, HB and BS genotypes for WW respectively. This gives opportunity for direct paternal heterosis to be used in crossbreeding systems with purebred A dams. Alternatively, since the B breed had a true ability to increase the expected BW in the A dam, it is suggested that a specific or rotational crossbreeding system which involves S and A dams that are mated with either H or B (only on mature dams) sires for the production of weaner calves under sweet veld conditions, be used. The data were also used to estimate the additive and non-additive effects for fitness traits in the two- and three-breed crosses. The average direct heterosis contributions were +14.9, +109.1, -162.7, +21.0 and 15.4% respectively for CR, MB, MP, WP and WR for ten two breed genotypes. Similarly, the average maternal heterosis effects in four A crossbred dam genotypes were 0.0, -87.5, +97.7, -1.9 and -7.4% for the fitness traits respectively. The HA genotype had the highest expected F of 83.1% in two-breed genotypes. The direct heterosis contributions in the HA genotype were +21.7, -2.3, -5.8, +28.3 and +30.1% percentage units respectively and the maternal contributions were -8.2, -2.4, +1.6, -6.4 and -11.6 for the traits respectively. The expected phenotypic values for improved traits in the HA and AHA genotypes were 94.9 versus 96.4% for CR, 92.2 versus 96.3% for WP and 83.1 versus 86.8% for WR (MB and MW remained unchanged). Crossbreeding the A dam line with the B sire line resulted in improved expected WR: 66.7 versus 80.2% in BA. Backcrossing the BA genotype decreased WR. This could mainly be explained by the increased expected MW; 3.3% in the A versus 6.0 and 15.6% in the BA and ABA genotypes respectively and the lower expected WR of 72.8 and 74.5% in the ABA and BBA genotypes respectively. While the SA genotype had an improved expected WR of 78.4% compared to the A genotype (66.7%), the WR in the ASA progeny was the lowest of all genotypes (60.4%). The low expected WR of the SA genotype could be explained by the increased expected MB of 5.3 versus 2.2% and MW 5.7 versus 3.3% of the A breed. The poor performance of the SSA genotype could be ascribed to an increase in MB and MW which was 7.3 and 4.3% respectively. The ACA, AHA and BHA genotypes had the highest expected WR of 86.9, 86.8 and 83.0% respectively. A specific crossbreeding combined with a terminal sire system is suggested to increase fertility in the A breed. Rotational systems will not have the same advantage since backcrossing the CA or HA dams to their respective sire lines would decrease the WR to 64.2 and 73.1% respectively. Alternatively, CA, HA or CH crossbred sires could be used on purebred A dams in a specific crossbreeding system. These genotypes had the largest direct heterosis effect on WR of all ten two-breed genotypes (36.5, 30.1 and 30.8% percentage units respectively). In a specific two-breed system the HA genotype would maximize WR. Although the average direct heterosis effects were unfavourable (-2.1 and -13.0 g/day respectively) for feedlot gain (FG) and carcass gain CG), feed conversion ratio (FCR) was -2.3% (a desirable effect). The average maternal heterosis effects for the feedlot traits were undesirable in the four A crossbred dam genotypes (-1.3, -7.4, and +0.9% respectively) for all the traits. Although these average heterosis effects suggest that feedlot traits do not benefit from crossbreeding, selected genotypes offer opportunity to increase feedlot production efficiency. As purebred the A compared less favourably in feedlot traits with Bos taurus breeds. However, it was evident that the A dam in two-breed crossbreeding could outperform the purebred S and Bos taurus crossbred dam lines in most of the these traits. The average direct heterosis contributions to feedlot traits in ten two-breed genotypes for the S, B, C and H as sire lines were -2.1, -13.0 (undesirable) and -2.3% (desirable) for feedlot gain (FG), carcass gain (CG) and feed conversion rate (FCR) respectively. Similarly, the average maternal heterosis effects for the feedlot traits in the four A crossbred dam genotypes were -1.3, -7.4, and +0.9% (undesirable) for FG, CG and FCR respectively. However, the A dam could be utilized in two-way crossbreeding systems with a terminal sire such as the C. The CCA genotype had expected average FG, CG and FCR of 1376.8 g/day, 781.2 g/day and 6.0 kg/kg respectively. Alternatively, the paternal heterosis contributions from BA, HA, SA, BH, BS and HS sire lines were also favourable. The aforementioned genotypes could thus be used as sire lines on purebred A dams to improve feedlot traits. It should however be noted that the data did not take cogniance of the genetic trends in the traits and the effects on heterosis parameters in any of the breeds since the conduction of the crossbreeding experiments. Heterosis units are therefore not directly applicable.
Open Access
Characterization of rangeland resources and dynamics of the pastoral production systems in the Somali region of eastern Ethiopia
(University of the Free State, 2006-05) Gezahegn, Amaha Kassahun; Snyman, H. A.; Smit, G. N.
The study was conducted in the Somali region of eastern Ethiopia, with an arid to semiarid climate. The study aimed at the characterization of the rangeland resources, assessing the current condition of the rangeland, understanding pastoral perceptions on rangeland degradation and developing drought feeding strategies for livestock. Three experimental sites, representative of the three predominant vegetation types of eastern Ethiopia were selected. They were the arid Asbuli grassland (used as grazing area for large and small ruminants), the arid Aydora open savanna (bush-grassland: entirely used for grazing/browsing by all types of livestock), and the semi-arid Hurso closed savanna (bushland: selected for its importance as browsing for camels and goats). A degradation gradient was identified in each of the three vegetation types, where the botanical composition was surveyed and the rangeland condition assessed. The perceptions of the pastoralist on rangeland degradation were also quantified. The dry matter production of both the herbaceous and woody layer was determined, while the grazing and browsing capacity calculated. Key forage species were identified and the grazing pattern of various livestock species along the degradation gradient studied. The soil seed bank regeneration potential was assessed in a greenhouse experiment and the response of cattle, sheep and goats to a simulated drought, in terms of reduced fodder, was conducted under controlled conditions. The results of the study confirmed the existence of severe rangeland degradation that occurred since 1944 and which was aggravated after the 1974 drought. This contributed to an increase in the number of poor households. The average livestock holding per household declined from 809 Tropical Livestock Units (TLU) before 1974 to 483 TLU after 1974. Livestock holding shifted from a predominance of cattle to small ruminants, which are able to utilize the degraded rangeland more effectively. Camels are now the most important livestock species in terms of milk and meat production, mainly due to their ability to tolerate drought. The abundance of herbaceous plants, basal cover, dry matter production and grazing capacity was found to be higher in the benchmark sites compared to the other rangeland conditions. There was also a corresponding increase in percentage bare ground, soil compaction and soil erosion along the degradation gradients. Over-grazing and overutilization through continuous grazing of the herbaceous layer were identified as the main causes of these differences. Rangeland condition was observed to significantly influence the grazing behaviour of livestock in terms of plant species selection, grazing intensity and intake per animal. When forage sources were adequately available, animals selected fever plant species. As forage resources declined the animals spend more time grazing and more species selected, including less palatable species. The number of bites, intake per bite and intake as a percentage of the animal’s body mass also increased as the rangeland become more degraded. Acacia nubica and A. mellifera were identified as aggressive encroaching species in the Aydora open savanna and Hurso close savanna. The Aydora open savanna experienced extensive encroachment by woody plants with increasing plant densities across the degradation gradient. The Hurso closed savanna experienced an opposite trend where severe deforestation and a loss of valuable browse species occurred, mainly as a results of over cutting of the woody plants for firewood, charcoal making, construction and the clearing of the land for planted crops. The study on the soil seed bank of soil collected along the various degradation gradients showed a high abundance of plant seed present in the soil, confirming the potential of the area for rangeland restoration. As expected the body weight losses of all livestock species in the controlled feeding trial were highly correlated with the reduction in daily dry matter feed. More than 50% of the animals showed pronounced emaciation and physical weakness and 25% of the cattle and goats collapsed and died within ten weeks after the trial started. This explained the large scale mortalities of livestock during prolonged droughts. Drought must be accepted as part of the pastoral life and there should be an adequate early warning system regarding livestock feed availability and strategies of appropriate mitigation strategies. More realistic stocking rates is the obvious solution to the avoidance of stock losses during droughts, but in view of the well established culture of the pastoralists it is highly doubtful if they will be willing to reduce their animal numbers. In conclusion, the experimental results indicated the existence of genetic variability among the various Somali livestock breeds regarding the tolerance to feed shortages and in rates of compensatory growth. This demonstrates the opportunity for improving the genetic composition of the Somali herds through selection.
Open Access
Comparison of genetic and immunological responses to tick infestation between three breeds of sheep in South Africa
(University of the Free State, 2016) Thutwa, Ketshephaone; Van Wyk, J. B.; Cloete, S. W. P.; Dzama, K.
𝑬𝒏𝒈𝒍𝒊𝒔𝒉 The study investigated genetic parameters and immunological responses to tick infestation in three South African sheep breeds (Namaqua Afrikaner [NA], Dorper and SA Mutton Merino [SAMM]). The study aimed to estimate genetic and crossbreeding parameters for tick count (TC) and weaning weight (WW), to examine the histology of tick attachment and control sites, to select reference genes for normalizing gene expression data in this study, to compare cytokines gene expression at tick attachment and control sites and finally to compare cutaneous hypersensitivity reactions to unfed larvae extracts (ULE) of Rhipicephalus evertsi evertsi between NA, Dorper and SAMM sheep. Genetic parameters for WW and TC were estimated using data of lambs maintained on the Nortier Research Farm from 2010 to 2015. Firstly, data of purebred commercial Dorper and SAMM lambs were combined with data of their reciprocal crosses to assess breed effects and the possible effect of non-additive genetic variation on WW and TC. In the second analysis, data of purebred commercial Dorper lambs were combined with data of the unimproved, indigenous NA and the NA x Dorper cross. In Analysis 1 the coefficient of variations (CV) were 24%, 95% and 50% for WW, untransformed total TC and square root transformed total TC, respectively. Genotype affected WW but not TC. A heterosis estimate of approximately 4% was derived for WW. A single-trait h² estimate for TC was 0.11±0.09. A model analysing across-genotype h² yielded a slightly lower h² estimate of 0.08 ± 0.07. In Analysis 2 the CV were 27% and 55% for WW and square root transformed total TC, respectively. WW and TC were affected by genotype. WW exhibited heterosis amounting to 8.5% while the corresponding value for TC amounted to -23%. The single-trait h² estimate for TC was 0.06±0.05. A model analysing across-genotype h² yielded a substantially higher h² estimate of 0.27±0.07. These results suggest that genetic variation in TC was primarily associated with differences among genetic groups while differences between individual animals within genetic groups were not as important. Heterosis estimates for WW were variable between two analyses, but within ranges reported in the literature. This study established significant variation in TC between sheep genotypes when the indigenous NA breed formed part of the analysis. The NA x Dorper cross resembled the improved Dorper breed for WW but the unimproved, resistant NA for TC and exhibited worthwhile levels of heterosis for both traits. Indigenous ovine genetic resources may be instrumental in providing genetic material for adaptive traits in environments susceptible to high levels of tick infestation. Further research is required to elucidate the role that adapted indigenous ovine genetic resources may play in an integrated tick management strategy under conditions characterised by high levels of tick challenge. A histological study was conducted to assess histological features at tick attachment and control sites in pure breeds. Skin biopsies were examined using routine histological techniques for immunological cell infiltration and skin reactions. Marked variation in immunological responses to tick attachment within and between sheep breeds was observed. There were differences between the attachment and control sites in most of the skin changes (defects) except for four skin defects in the NA. However, all breeds had similar frequencies of skin defects at tick attachment sites. Tick attachment sites were more likely to be infiltrated by cells within as well as across breeds. The NA and SAMM breeds tended to demonstrate greater cellular infiltrations of specific leukocytes at tick attachment sites compared to Dorpers. Basophils, mast cells and eosinophils were increasingly recruited at tick attachment site in NA ewes compared to the Dorper and, occasionally, the SAMM breeds. These results suggest the importance of these cells in sheep resistance to tick infestation. Tick genera influenced the recruitment of neutrophils to tick attachment sites. Tick gender, sampling site as well as tick engorgement level did not affect the number of immunological cells. Further studies should be done with one tick species at a time to better comprehend the species-specific impact of tick attachment to animals belonging to divergent sheep breeds. Five genes (18S, GAPDH, YWHAZ, B2M and SDHA) were tested for their stability. SDHA, YWHAZ and B2M were the most suitable reference genes recommended by geNorm analysis for normalizing gene expression data in sheep skin. These findings will assist in normalizing data in gene expression studies at tick attachment and control sites of the NA, Dorper and SAMM breeds. This study suggested that no reference gene is stably expressed in different experimental conditions. The expression of IL-1β, IL-8, CCL2 and CCL26 was quantified in real-time qPCR. IL-1β and IL-8 were more highly expressed at tick attachment than at control sites. NA ewes expressed IL-1β more at tick attachment sites than Dorpers. The NA breed was also more likely to upregulate the expression of the CCL2, CCL26 and IL-8 genes at tick attachment sites compared to control sites than the other breeds. This indicates that IL-1 β, CCL26 and IL-8 may play a part in resistance or susceptibility of sheep to tick infestation. The differences in expression of the two chemokines between the resistant NA and more susceptible SAMM and Dorper imply that the NA breed could be able to overcome the anti-chemokine activity of tick saliva. ULE of R. evertsi evertsi induced hypersensitivity reactions in all the breeds. The indigenous NA displayed stronger reactions, immediate and delayed, than the commercial breeds. The results suggest that cell-mediated immune responses are invoked to fight against tick infestation in the NA. The hypersensitivity reaction may be used as a phenotypic marker to select animals or breeds that are more resistant to tick infestation. It is well-known that challenge-based research for promoting resistance to pathogens is under scrutiny from an ethical and welfare perspective. The methods employed here could be refined to enable routine evaluation of valuable animals without resorting to more invasive strategies, such as allowing adequate natural challenge to accrue over time in selection candidates. Overall, the component studies reported in the thesis increased the present understanding of ovine tick-host interactions and factors contibuting to breed differences in tick loads. ___________________________________________________________________
Open Access
Crude protein and mineral status of forages grown on Pellic Vertisol of Ginchi, Central Highlands of Ethiopia
(University of the Free State, 2002-11) S/gebreal, Lemma Gizachew; Smit, G. N.
The study was conducted at Ginchi, which is situated in the western Shoa zone of the central Ethiopian highlands. The main aim of the study was to assess the crude protein (CP) and mineral status of feeds produced in the Vertisol area of Ginchi by relating them to pasture management, seasonal and/or soil factors. Aspects of the farming systems that relate to feed resource management, utilization, constraints and opportunities were also investigated. The N and mineral element status of the soil and the feeds were evaluated during the dry and wet seasons of 2001 by analysing samples collected from adjacent 18 year round grazed grassland (YRG) plots, 12 seasonally stock excluded grassland (SSE) plots, 10 tef (Eragrostis tef) and 9 grass pea (Lathyrus sativus) plots, and noug (Guizotia abyssinica) seedcake samples obtained from oil extracting plants. The results of the farming systems study demonstrated a strong inter-dependence between crop and livestock subsystems. Livestock rely on crops for their diets as much as the latter do on livestock for traction power and manure. Stored feed supplies are preferentially fed to working oxen, milking cows and animals intended for sale. The period extending from the late dry season (March-May) up until the mid wet season (July) appeared to be the time when feed shortages were most critical. Smallholders try to cope with the problem through efficient use of SSE, grassland, crop residues and crop weeds. Occasionally they also provide domestic herbivores with locally produced supplemental feeds, common salt, mineral rich soil or mineral water. Soil samples were analysed for particle size class, pH, organic matter (OM), cation exchange capacity (CEC), N, P, Ca, Mg, K, Na, Fe, Mn, Cu and Zn. Most of these soil parameters differ markedly (P<0.05) between the different land use systems. Parameters such as OM and total N in particular were very high in grassland soil in comparison to soil under cropping systems (P<0.01). The results also revealed a substantial across site variation of these soil parameters. For native pastures, the type of pasture management had a considerable influence on floristic composition, herbage CP and mineral concentration. Compared to the YRG grassland the SSE grassland contained a higher proportion of herbaceous species with superior CP and mineral concentrations. The CP and mineral contents of YRG grassland exhibited marked changes with the advance of the season (P
Open Access
Cryopreservation of South African indigenous ram semen
(University of the Free State, 2012-05) Munyai, Pfananani Hendrick; Nedambale, T. L.; Greyling, J. P. C.; Schwalbach, L. M. J.
Semen was collected from the indigenous Damara, Namaqua Afrikaner, Pedi and Zulu rams. Hundred and twenty eight (128) ejaculates were collected throughout the entire study, with semen being collected twice a week (every Monday and Tuesday) from each ram, using the electro-ejaculator. Ejaculates were collected in graduated test tubes, placed in a thermo flask at 37°C, and transported to the laboratory for evaluation within 1h interval. The raw or fresh undiluted semen was then microscopically evaluated for volume, concentration, pH and sperm motility. The sperm concentration was determined with the aid of a spectrophotometer (Spermacue®) and the semen pH using a pH meter (Microprocessor pH/mV/°C Meter Hanna HI 931401). A Computer Assisted Sperm Analysis (CASA) system was used to evaluate the different sperm motility characteristics. All data were analysed using the statistical GenStat® program. The analysis of variance (ANOVA) was used to test for significant differences between treatments. Characterization of the South African indigenous ram sperm viability (percentage live/dead) of the semen samples was determined, using an eosin/nigrosin stain (60μl eosin/nigrosin and 6μl semen), in a thin smear. All sperm cells were evaluated on the same day of semen collection with the aid of a fluorescent microscope (BX 51TF), using an oil immersion objective (X100 magnification). The live sperm fluoresced green, while the dead cells stained red. The live sperm cells were further categorized as morphologically normal or abnormal. The volume of the indigenous ram ejaculates ranged between 0.4 and 0.9mL. The sperm concentration recorded in this study ranged between 0.9 and 1.3x109 sperm/mL, which are much lower when compared to other studies. The semen pH recorded in this study ranged between 6.5 and 7.3 and the sperm abnormalities ranged between 5.2% and 8.2% – which is regarded as acceptable for fertilization. To test the effect of storage temperatures on the viability of the diluted ram semen stored for different periods of time, the same procedure of semen collection and semen evaluation was followed. After the initial semen evaluation, all semen samples were pooled and diluted equally in an egg yolk citrate extender in the ratio of 1:1(v/v). The pooled semen sample was then divided into two portions, one sample being stored at 5ºC, and the other at 15°C, following storage periods of 3, 6, 9, and 24h respectively. Sperm characteristics were then recorded for each interval of storage. In general the percentage total motile sperm recorded after a 24h period of storage at 15°C was higher (61.2%), compared to that at 3h (51.4%), 6h (50.1%) and 9h (50.6%). From the results of this study it was concluded that diluted ram semen can be successfully stored for 24h at 15°C, retaining sperm motility for the application of AI. When evaluating the effect of glycerol as a cryoprotectant, in the diluted ram semen stored at two temperatures for different periods of time, the same procedure for semen collection and evaluation was followed. After initial evaluation, all semen samples were pooled and diluted equally with an egg yolk citrate extender containing 14% glycerol in the ratio of 1:1 (v/v), resulting in a final glycerol concentration of 7%. The pooled semen sample was then divided into two portions, one sample being stored at 5ºC and the other at 15°C, for periods of 3, 6, 9, and 24h. Sperm characteristics were recorded at each interval of semen storage. Semen stored at 15°C recorded a 48.3% total motile sperm after 3h of storage, but this increased to 50.4% following 24h of storage. The percentage of total motile sperm remained relatively constant at 40% after 3h of storage and 40.8% after 24h in the semen stored at 5°C. The addition of glycerol as a cryoprotectant demonstrated a protective effect on the sperm motility characteristics of sperm stored at both 5°C and 15°C for up to 24h of storage. The effect of different glycerol inclusion levels in the diluent, on the indigenous ram semen characteristics following cryopreservation were evaluated. The same procedure for semen collection was followed and semen was subjected to the initial evaluation comprising sperm concentration, semen pH and sperm motility. After initial evaluation of the ejaculates, the semen samples were diluted with an egg yolk citrate extender (EYC) fraction A (without glycerol), in the ratio of 1:1 (v/v) and cooled over a period of 2h to 5°C. All ram ejaculates were pooled and then divided into 4 portions treatment (groups). The first group was diluted with EYC (fraction A), which served as a control and the other 3 groups with EYC (fraction B) contained 7, 10 or 14% glycerol (GLY) in the ratio of 2:1 (v/v), making final glycerol concentrations of 2.3, 3.3 or 4.7% respectively. The semen samples were equilibrated for 2h and then loaded into 0.25mL semen straws. The straws were frozen in liquid nitrogen (LN2) vapour, whereafter semen straws were plunged into the LN2 (-196°C). The semen straws were thawed 7 days later, in a water bath (37°C) for 30 seconds. The sperm characteristics (motility and velocity) were microscopically evaluated using the Sperm Class Analyzer® (CASA) system. A 10% glycerol inclusion rate recorded a higher percentage of total motile sperm (15.6%), compared to the 7% glycerol (12.8%) and 14% glycerol (8.5%) inclusion levels, although all these differences were not significant. This study demonstrated that an egg yolk- citrate extender containing 10% glycerol can be used to cryopreserve indigenous ram semen effectively, based on the sperm motility characteristics. The low sperm motility results recorded when semen was cryopreserved in an extender containing 14% glycerol also indicated a degree of toxicity of glycerol at high inclusion levels in the semen extender. Regarding the conventional slow cryopreservation (programmable freezer) of ram semen versus semen cryopreservation in liquid nitrogen vapour, the same procedure for semen collection and evaluation was followed. After the initial evaluation of the raw semen samples, all ejaculates were pooled and then diluted using an egg yolk - citrate extender (EYC) fraction A (without glycerol), in the ratio of 1:1(v/v) and cooled over a 2h period at 5°C. After equilibration, the pooled semen sample was further diluted with EYC fraction B, containing 14% glycerol, in a ratio of 2:1(v/v)resulting in a final glycerol concentration of 4.7%. The pooled semen sample was then further equilibrated and loaded into 0.25mL semen straws. Half of the straws were frozen in liquid nitrogen (LN2) vapour and then plunged into the LN2. The other half of the semen straws were frozen with the aid of a programmable freezer. After 7 days, the semen straws were thawed in a water bath at 37°C, for 30 seconds. The sperm characteristics (sperm motility and velocity) were microscopically evaluated using the CASA system. From the findings in this study, it can be concluded that a controlled rate of semen cooling gave superior sperm motility results (15.3±3.0%), compared to semen frozen in LN2 vapour (8.8±0.9%). It should be noted that programmable freezers are costly, when compared to the liquid nitrogen vapour technique. Due to the fact that sperm motility differences recorded were not significant, it is suggested that the freezing of semen on a small scale be done using the LN2 vapour technique, without any significant decrease in sperm motility or possible fertility.
Open Access
The degradable protein requirements of beef cattle consuming winter forage hay from the pure grassveld type
(University of the Free State, 2010-05) Bareki, Mathuto Abigail; Van der Merwe, H. J.; De Brouwer, C. H. M.; Ferreira, A. V.
A trial was conducted to determine the total rumen degradable protein intake (RDPI) required to maximise the digestible organic matter intake (DOMI) of beef cows consuming low quality grass hay from the Northern variation of Cymbopogon-Themeda pasture type (pure grassveld). Thirty five pregnant Afrikaner x Simmentaler crossbred cows (±517.08kg, SD 53.06) were randomly allocated to 5 treatments. Treatments provided the following RDP levels/cow/day 0g, 180g, 360g, 540g and 720g. A RDP source, calcium caseinate (90% crude protein (CP) on dry matter basis and 100% rumen degradable) was used and mixed with molasses based concentrate. The cows had ad lib access to low quality grass hay (2.26% CP, 73.94% neutral detergent fibre). The trial period consisted of 14 days adaptation, 21 days intake study and 7 days digestibility study. No statistical significant (P > 0.05) influence of RDP level on the apparent digestibility of dry matter (DM), organic matter (OM) and neutral detergent fibre (NDF) was detected. The grass DM intake (DMI), DOMI and metabolisable energy intake (MEI) increased in a linear and quadratic manner (P < 0.05) with increasing levels of supplemental RDP. The single broken-line model predicted DOMI/kg BW0.75 with higher accuracy (R2 = 0.45) than the quadratic regression procedure (R2 = 0.07). According to this model 4.03g daily RDPI/kg BW0.75 or 8.07% RDP of DOM was required to maximise DOMI of pregnant beef cows consuming winter grassveld hay. In a second trial the potential to substitute true protein with urea was investigated. Urea replaced 0%, 25%, 50%, 75% and 100% of the natural supplemental RDP. The same procedure as described in the first trial was followed. The increasing proportion of urea did not significantly (P > 0.05) influence the apparent digestibility of DM, OM and NDF. There was a linear increase in grass DMI (P = 0.0355) at increasing levels of urea, with the highest intake observed when urea was used as a sole source of nitrogen (N). DOMI and MEI increased in both linear and a quadratic manner (P < 0.05) with increasing levels of urea. The molar proportions of acetic, propionic and butyric acid were not affected (P < 0.05) by the substitution of urea, while the molar percentages of iso-butyric and iso-valeric acid were significantly decreased (P < 0.0001) with increasing urea levels. Ammonia N increased linearly (P = 0.0426) while the ruminal pH was not affected (P > 0.05) by increasing the proportion of urea. It seems that urea can be the sole RDP source in supplements for pregnant beef cows consuming the low quality grass hay. In the third trial, the influence of replacing natural protein with urea on the performance of beef cows grazing natural winter grassveld was investigated. Pregnant Afrikaner x Simmentaler crossbred cows were randomly allocated to the two treatments. The number of cows per treatment varied between 18 and 28 each year. The trial was executed over four consecutive winter periods from 2003 to 2006. The treatment licks comprised of: 1) 100% supplemental RDP from urea and 2) 50% supplemental RDP from urea and 50% from cottonseed oilcake. Lick provision was controlled to ensure the total RDPI as recommended in the first trial. Increasing the proportion of supplemental RDP from urea did not have a significant (P = 0.9938) effect on the end live mass of the cows. The urea levels did not significantly influence (P > 0.05) weaning mass, corrected weaning mass and average daily gain of the calves. The lack of significant lick treatment effect on live mass, body condition score and performance of the calves suggests that urea can be used as a sole source of RDP.
Open Access
The demography and population status of lions (Panthera leo) in the Mana Pools National Park, Zimbabwe
(University of the Free State, 2008-11) Monks, Norman John; De Waal, H. O.
English: Demographics of the lion population in the Mana Pools National Park were studied between 2001 and 2007. No detailed work had previously been carried out on this subject in the park. Demographic data was obtained from six prides, with two prides (Chitake and Jesse) being on the Zambezi Valley floor at the base of the Zambezi Escarpment in the south, and four prides on the Zambezi floodplain in the north. The Zambezi floodplain in the Mana Pools National Park is 95.5 km² in extent and in area comprises 11.2% of the park. Approximately 46% of the adult lion population occurs on the floodplain where approximately 63% of the lion prey base in the park is found. Not all prides could be studied at the same intensity, however, demographic data was obtained for all six prides. The Nyamepi pride on the floodplain was the most intensely studied. A population estimate of 67 adult and sub-adult lions was made for the Mana Pools National Park. Overall density throughout the park was 3.05 lions/100 km². Density ranged from 0.65/100 km² in the escarpment which held 0.3% of the prey species taken by lions to 12.7/100 km² on the floodplain. There were 1.8 adult males to 3.3 adult females and all prides were attended by a male. Mean group size (adults and sub-adults) was 7.8 (range 5-11). The adult and sub-adult age class made up 70.7% of the population and large and small cubs made up 29.3% of the population. Cub survival to one year of age was 66.7%. Females produced their first litter between 43-53 months of age and cohorts of cubs were produced on average every 38.5 months. Pride males had an average tenure with the pride of 33.25 months and sub-adult males dispersed from the pride between 36-57 months with a mean of 39.8 months. Home ranges varied on the floodplain from 28.1 km² to 278 km² and from 50.2 km² to 379.3 km² on the valley floor. The floodplain Nyamepi pride males had a home range two and a half times that of the females. Only the Valley floor lions had differences in dry and wet season home range size (dry season 57.7 km² and wet season 379.3 km²). Demographic variables, when compared to other lion populations in similar habitat in protected areas in Africa, did not differ and the Mana Pools National Park lion population appears to be normal. The Mana Pools National Park is surrounded in the west and east by Safari areas (administered by ZPWLMA) and has no man-made or natural barriers between them. No work was carried out on lions in the surrounding Safari areas but it was found that males frequently made excursions into the Safari areas (one collared male was shot in Chewore Safari area 80 km from the darting site in Mana Pools). Lions also frequently crossed the Zambezi River into the Lower Zambezi National Park, Zambia. It is presumed that there is a two-way movement between the Mana Pools National Park and Safari areas and the Park and the Lower Zambezi National Park, but could not be confirmed in this study. The spotted hyaena population in the Mana Pools National Park was found to be in the low-medium category when compared to other populations in protected areas in Africa (Purchase, 1999). All data accrued during the present study showed that this population do not pose a threat to lion conservation in and around the Mana Pools National Park.
Open Access
Determination of some blood parameters in the African lion (Panthera leo)
(University of the Free State, 2008-11) Erasmus, Heidi Louise; Schwalbach, L. M. J.; De Waal, H. O.
The goal of this study was to generate a database of laboratory results for African lion (Panthera leo) blood to obtain reliable reference ranges to augment what is currently available in literature. Also to investigate the possibility of age and sex having an influence on these reference ranges. The specific objectives of this study were: o to determine reference values for haematological and biochemical blood variables for lions bred in captivity, as a function of age and sex; o to evaluate the Beckman Coulter Ac•T 5diff Haematology Analyzer for lion differential white blood cell analyses; o to determine morphometric measurements and establish reference growth curves (and range reference values) for lions bred and reared in captivity as a function of age and sex; o to determine reference values for some practical and meaningful body measurements and their correlations. This study was conducted on three lion ranches in the Free State province and at the Bloemfontein Zoological Gardens (Bloemfontein Zoo) with captive lions (Panthera leo) of both sexes and ages ranging from three months to nine years. Lions were divided into four age groups according to published literature. Animals were chemically immobilized (darted) with Zoletil® 100 at 4 to 5mg/kg in their holding camps and moved to a shaded place as soon as the drug had taken its full effect. Blood was collected into three different types of blood collection tubes and body measurements were taken. This was all done as fast as possible before the effect of the immobilizing drug could wear off. In some cases it was necessary to give an animal a top-up dose to prevent it from waking up too quickly. Animals were moved back to their holding camps to fully recover from the immobilization. Blood analyses done with the Ac•T 5diff Haematology Analyzer from Beckman Coulter® for haematological parameters was conducted within 30 minutes after blood collection. Blood for biochemistry parameters was centrifuged, serum collected and cryo preserved at -20°C until it could be taken to the laboratory for analyses. Blood smears were made on the lion ranches and Bloemfontein zoo immediately after the analysis with the Ac•T 5diff Haematology Analyzer, fixed and packed for transport to the laboratory. At the laboratory the serum was used for biochemistry analyses, using standard laboratory techniques. Blood smears were stained and examined under a light microscope for the differential white blood cell count by means of the manual-visual method. Results were statistically analyzed to determine reference ranges and the influence of age and sex on these reference range values for the different parameters, were considered. Body measurement were also statistically analyzed to determine correlations between body weight and different other measurements. These correlations were then used to determine if it will be possible in a field situation to use the age and sex of an animal together with a certain body measurement to estimate body weight accurately, if actual weighing was not possible. From these analyses it was concluded that age and sex do have an influence on blood analysis and blood reference ranges for the African lion (Panthera leo). Unfortunately, it differs between parameters and there is not one rule to apply. The conclusion could also be made that body weight could be determined by measuring the head length of an animal. More research is warranted to obtain more data set and establish range reference values that can be validated and used with a high degree of confidence in the lion breeding industry.
Open Access
The development of breeding objectives for Holstein and Jersey cattle in South Africa
(University of the Free State, 2009-11) Banga, Cuthbert Baldwin; Neser, F. W. C.; Garrick, D. J.; van der Westhuizen, J.
A sound breeding objective is the basis for genetic improvement in overall economic merit of animals. Breeding objectives for Holstein and Jersey dairy cattle breeds in South Africa were developed in the current study, using a systematic approach. First, a logical framework with a profit focus was utilised to develop plausible selection goals for the pasture-based and concentrate-fed dairy production systems in South Africa, leading to an exhaustive list of objective traits influencing these goals and subsequently their possible selection criteria. Next, economic values were calculated for those objective traits for which there was adequate bio-economic data, viz.: milk volume, fat yield, protein yield, live weight, longevity, calving interval and somatic cell score. A bioeconomic model, simulating typical South African pasture-based and concentrate-fed herds, was used to calculate economic values by determining changes in profit arising from an independent unit increase in each trait. Alternative payment systems of four major milk buyers in South Africa were used. Relative economic values, standardised to the value of protein, were used to compare the relative importance of traits across breeds, production systems and payment systems. Protein yield, fat yield and longevity consistently had positive economic values and the converse was true for body weight and calving interval. Economic value for volume was positive or negative, depending on whether the payment system paid for it or did not. Economic values were reasonably robust to fluctuations in the cost of feed and price of beef; with the exception of fat, whose value became negative beyond the feed price of ZAR3.50. Protein was, overall, the most important trait, although volume, live weight, longevity and somatic cell score were more important in some situations. Calving interval was the least important trait, its value ranging from 4 to 22% compared to that of protein, probably because the model used underestimated its value. Sire rankings on aggregate EBVs based on these economic values did not differ much across breeds, production systems and payment systems, most rank correlations falling in the range 0.70-0.99. A single breeding objective may therefore be used for both the Holstein and Jersey breeds, across the different production and payment systems. The basis for multiple-trait selection in the major cattle breeds in South Africa has thus been developed. Considerable work, however, needs to be done to enhance this breeding objective as well as facilitate its wide adoption by industry.
Open Access
The development of economic selection indices for the Simmentaler breeds in South Africa
(University of the Free State, 2004-11) Kluyts, Johan Francois; Neser, F. W. C.; Bradfield, M. J.
English: The purpose of the first chapter was to give a short introduction to the study. Although there were exponential increases in knowledge, there are still fields of study where there is little understanding and enormous gaps relating to information. A short history of the development of cattle was presented, with special reference to the Simmentaler breed. The objectives of this study were then stated. These objectives were: the definition of breeding objectives, derivation of economic values and development of economic selection indices for the Simmentaler breed in South Africa. 2. In Chapter 2 the development of breeding objectives and the derivation of economic values were reviewed. There seems to be general consensus that definition of breeding objectives should be the primary step in the design of structured breeding programs. Development of the breeding objective can be described in terms of the following phases: specific ation of the breeding, production and marketing system, identification of sources of income and expense in commercial herds, determination of biological traits that influence income and expense, derivation of economic values, choice of selection criteria, and estimation of phenotypic and genetic parameters. The modeling methods to derive economic values can be divided into simulation, dynamic programming and profit functions. 3. In Chapter 3 the important traits, which should be considered for the development of breeding objectives, as well as the criteria to be included in the selection index were reviewed. Traits were classified as fitness-, production-, product-, input-, type- and behavioural traits. The decision whether or not to include a trait in the breeding objective depends on the relative economic value of the trait, the potential for genetic improvement and the possibility of accurate and cheap measurement. Several traits determine economic efficiency, and the required balance of these traits is likely to differ between different production systems. 4. The purpose of Chapter 4 was the development of a general breeding objective for the Simmentaler breed in Southern Africa as well as the derivation of economic values for beef production traits. Income was partitioned between weaners (steers), surplus heifers and cull cows. Expenses were calculated for all classes and included feed cost, husbandry cost and marketing cost. Economic values for weaning weight (direct), weaning weight (maternal), yearling weight (400 days), final weight (600 days) and mature cow weight were derived as partial derivatives of the profit equation. These values, expressed per genetic standard deviation, in South African Rand per cow, corrected with the discounted gene flow and diffusion coefficient methods (in brackets) are, 25.57 (75.01), 15.21 (47.97), 28.49(83.63), -13.95 (-40.79) and -69.29 (-63.39) respectively. 5. The objectives of Chapter 5 were to expand the Simmentaler breeding objective by inclusion of functional traits and to derive economic values for the functional traits calving rate, days -to-calving, calving-ease (direct) and calving-ease (maternal). It was assumed, for these categorical traits, that there is an unobserved underlying normal distribution of the sum of genetic and environmental values, and that the phenotypic category is defined by threshold values on this distribution. The consequences of a change in fitness included changes in costs, changes in culling rate, number of barren cows and the number of surplus offspring available for sale. Results emphasised the relative importance of fertility. Economic values, expressed per genetic standard deviation in South African Rand per cow, corrected with the discounted gene flow and diffusion coeffic ient methods (in brackets) are, 18.98 (15.27), - 93.82 (- 75.51), 1.08 (1.31) and 1.15 (1.08) for calving rate, days-to-calving, calving-ease (direct) and calving-ease (maternal), respectively. 6. The objectives of Chapter 6 were to expand the Simmentaler breeding objective by the inclusion of product quality traits and to derive economic values for dressing percentage, backfat thickness, tenderness and marbling. A method to derive economic values for these optimum traits was described. It was as sumed, for the categorical traits, that there is an unobserved underlying normal distribution of the sum of genetic and environmental values, and that the phenotypic category is defined by threshold values on this distribution. The consequences of a change in the mean performance of a trait include changes in the number of animals in different quality classes and as a result thereof, changes in the expected value of a carcass. Economic values, expressed per genetic standard deviation in South African Rand per cow, corrected with the discounted gene flow and diffusion coefficient methods (in brackets) are, 20.96 (61.50), 0.39 (1.14), -3.52 (-10.33) and 0.18 ( 0.52) for dressing percentage, backfat thickness, tenderness and marbling respectively. 7. The development of economic selection indices for an integrated Simmentaler production system was described in Chapter 7. The breeding objective was defined in terms of production-, functional- and product quality traits. Criteria included in the total index are birth- and weaning weight (direct and maternal), yearling weight, final weight, mature cow weight, days -to-calving, backfat thickness, tenderness and marbling. The total merit index (IT) for an integrated Simmentaler production system is IT = – 1.65 BWD – 1.99 BWM + 2.28 WWD + 1.76 WWM + 1.48YW – 0.50 FW – 2.02 MCW – 13.21 CD + 4.92 BF – 2.34 T + 12.77 M. The correlation between this index and the breeding objective is 0.987. The economic superiority, over the average progeny, of the progeny from the top 40% of animals selected on their ranking in the total index, is expected to be R116.49.
Open Access
Dietary fibre requirements of feedlot lambs
(University of the Free State, 2008-05) Smith, Pieter Schalk; Van der Merwe, H. J.; Ferreira, A. V.
No abstract available
Open Access
Die doeltreffendheid van proteïen- en energiebenutting deur vleisvarke
(University of the Free State, 1972) Smith, Gerhardus Adam; Van der Westhuizen, A. A.
Abstract not available
Open Access
The dynamics of bush thickening by Acacia mellifera in the Highland Savanna of Namibia
(University of the Free State, 2014) Joubert, David Francois; Smit, G. N.; Hoffman, M. T.
The dynamics of bush thickening by Acacia mellifera in the arid Namibian Highland Savanna was investigated. First, a conceptual state-and-transition model was developed, based on preliminary findings, personal observations and resultant insights. In this model it was proposed that two main states exist, an open, grassy state and a bush-thickened state. Each of these is subdivided into other states. An unstable transitional state with A. mellifera seedlings within the grass sward is a crucial juncture between the grassy and bush thickened state. In the model, the transition to this unstable state occurs after at least two, but more likely three, consecutive years of well above-average annual rainfall through seed production followed by germination and establishment. Only an interruption by fire, which has a high probability of coinciding with this establishment if the grass sward is lightly utilised, prevents a further transition to a bush thickened state. Fire returns the vegetation to a grassy state by causing an almost 100 % mortality of seedlings. If fire is absent through a lack of fuel (overgrazing) or fire is deliberately excluded, the transition to a bush-thickened state is a fait accompli, but may take decades to reach. Transitions from the bush-thickened state to a grassy state require drought and the associated fungal dieback, which accelerates the senescence of mature shrubs. The model proposes that a transition towards the unstable transitional state occurs rarely, due to the rarity of suitable climatic conditions (protracted period of consecutive years of above-average annual rainfall). The mechanisms of two key transitions were tested. Firstly, the transition to an unstable state through the en masse production of seeds followed by the successful establishment of seedlings after a protracted period of well above average rainfall was tested during a nine-year period (late 1998 to early 2007). Secondly, the transition back to an open grassy state during a potential establishment event, through the mortality of seedlings after a fire, was tested experimentally (2008 and 2009). Both of these studies confirmed the predictions of the model and the mechanisms proposed for these transitions. Preliminary evidence suggests that browsing by small herbivores, in particular lagomorphs, thins resultant thickets out through herbivory. Preliminary evidence also suggests that competition between grasses and seedlings does not directly stop the transition to a bush thickened state but may prolong the window of opportunity for a fire to be effective, through reducing the growth rate of seedlings and saplings. The findings are of relevance to management, and thus an expert system for rangeland management, with emphasis on bush thickening, was developed, based largely on the findings of this research. Preliminary historical evidence casts doubt upon the prevailing perception that bush thickening is mostly a phenomenon of the last half century, and, consequently, that bush thickening is the primary cause of the loss of rangeland productivity in the arid rangelands of Namibia during this period. The study suggests that fire in arid savannas is as important as it is in mesic savannas. A general principle could be stated as follows: The importance of the timing of fire in savannas increases with increasing aridity, whilst the importance of the frequency of fire in savannas decreases with increasing aridity.