Effect of different dietary energy levels on productive and reproductive traits in Dorper rams
| dc.contributor.advisor | Schwalbach, L. M. J. | |
| dc.contributor.advisor | Greyling, J. P. C. | |
| dc.contributor.advisor | Van der Merwe, H. J. | |
| dc.contributor.author | Bester, Nena | |
| dc.date.accessioned | 2015-10-09T09:18:06Z | |
| dc.date.available | 2015-10-09T09:18:06Z | |
| dc.date.copyright | 2006-05-31 | |
| dc.date.issued | 2008-02-19 | |
| dc.date.submitted | 2006-05-31 | |
| dc.description.abstract | English: A study was conducted to evaluate the effects of different dietary energy levels on the productive (ADG, FCR, body weight, carcass) and reproductive (scrotum, testes, semen) characteristics of young Dorper rams. The study was carried out in two phases at the University of the Free State campus in Bloemfont ein, South Africa. Out of a group of 60 rams, 36 animals that were successfully trained for semen collection with the aid of an artificial vagina (AV), were selected to be part of this study and housed in individual metabolic cages. During phase 1 of this study, 36 (11 to 12 months old) Dorper rams with a mean initial body weight of 42.0 ± 0.52kg were randomly allocated to 3 groups (n=12 per group). Each group was randomly assigned to one of 3 experimental diets (treatments), formulated on a crude protein, degradable protein, calcium and phosphorus equivalent basis. A medium energy (Me) diet was formulated according to the National Research Council standards (NRC) for young growing rams to serve as the control diet. The metabolisable energy (ME) content of this diet (Me) was increased by 15 % for the high energy (He) and decreased by 15% for the low energy (Le) diets respectively. The actual ME levels for the Le, Me, He: were 6.52, 8.09 and 9.39 MJ/kg, respectively. The rams received the diets and fresh water ad libitum during a 127 day trial period and were weighed once a week. Their ADG, FCR and ME/kg weight gain calculated and compared amongst groups. During this trial, a digestibility trial was conducted for 7 days (during week 14 of the trial), using 5 randomly selected animals from each treatment group. The amount of feed offered and consumed by each animal as well as the feaces excreted daily were recorded. The chemical composition of the diets and the feaces (dry matter, energy, crude and degradable protein) were determined. Semen was collected from each ram, every forthnight for 3 consecutive days, with the aid of an AV and evaluated for volume, overall sperm motility, forward progression, sperm concentration, % live sperm and % normal sperm. The semen samples were then diluted (using a one-step dilution method with a cryodiluent containing 5% glycerol), packed in 0.25ml plastic straws, equilibrated for 4 hours and cryoperserved (frozen) in liquid nitrogen vapour (-70 ºC). One week after freezing, the semen was thawed (38 ºC for 30 seconds) and evaluated for the same qualitative parameters as the fresh semen. The results were compared amongst groups for each collection time, using ANOVA for repeated measures analysis procedures of SAS. The energy level of the diet and the collection week as well as their interaction was used as independent variables, while the different semen parameters considered were the dependent variables in the model. When means differed significantly, the Tukey method was used to compare means. At the end of this trial period, 6 rams per group were randomly selected and slaughtered at a commercial abbatoir. After slaughtering the carcass characteristics (cold carcass weight, dressing percentage, carcass grade, shoulder circumference, buttock circumference, backfat thickness, eye muscle area, marbeling and kidney fat) were recorded and compared amongst groups. The scrotum (total weight, skin weight, fat and circumference), testes (volume and weight) and epidydimis (weight and volume) characteristics were also recorded and compared between groups, using ANOVA procedures of SAS. When means differed significantly the Tukey method was used to compare means. From the independent variables considered in the model, only the diet (ME level) had a significant effect on the parameters considered. In general, an increase in dietary energy level resulted in higher growth rates, better feed conversion rates, heavier carcasses, higher dressing percentages and greater fat deposition, both in the carcass, around the kidneys and in the scrotum (particularly in the neck region, over the testicular vascular cone). It seems that the energy requirements recommended by the NRC (1985) are not applicable for early mature Dorper replacement ram lambs, as those in the He group, (real ME level similar to NRC recommendations) deposited excessive fat in their body. Despite the significant differences induced by the He on the growth performance, carcass characteristics as well as on the scrotal and testicular characteristics of Dorper rams, no detrimental effects were recorded in their semen quantity, quality and cryotolerance. During the following 90 days (phase 2), the remaining rams (n=6 per group) were further maintained on the Le diet for 90 days. This was done to simulate the situation when over-conditioned (fat) rams bought at auctions are placed on low energy diets (veld). Other objectives of this trial phase were to evaluate if the fat deposits accumulated in the scrota of rams fed on high energy diets are mobilized during subsequent periods of moderate nutritional restriction and if these nutritional restrictions induce any changes on the semen characteristics of rams. During this phase of the trial, semen was collected, with the aid of an AV, every 3 weeks during 2 consecutive days. The semen was evaluated using the same procedures described for phase 1 of this study. The rams were slaughtered at the end of this trial period (90 days) at a commercial abattoir. After slaughtering, the carcass characteristics (cold carcass weight, dressing percentage, carcass grade, shoulder circumference, buttock circumference, backfat thickness, eye muscle area, marbeling and kidney fat), the testicular (volume and weight), the scrotal (weight, circumference, skin weight and fat) and the epididymis characteristics (weight and volume) were also recorded and compared amongst groups. Data was analysed statistically using the same procedures as described for phase 1. The results of this trial clearly indicated that the scrotal fat deposits of rams previously fed on the He diet are mobilized (at least partially) during subsequent periods of moderate dietary energy restrictions without adverse effects on semen quantity and quality. This is the first time that such finding is reported. Further research on the effect of high energy diets on subsequent ram fertility (short and long terms), as well as their reversibility are warranted. Different age groups, feeding regimes and other management practices must also be associated to high energy diets in order to fully evaluate the effect of these common practices on subsequent ram fertility. | en_ZA |
| dc.description.abstract | Afrikaans: Die studie is uitgevoer om die effekte van verskillende energiepeile in diëte op die produksie (GDT, VOV, liggaamsgewig en karkaseienskappe) en reproduksie - (skrotum, testes en semen) eienskappe in jong Dorperramme te bepaal. Die studie is in 2 fases by die Universiteit van die Vrystaat kampus in Bloemfontein, Suid-Afrika uitgevoer. Uit ‘n groep van 60 ramme, is 36 suksesvol afgerig vir semenkolleksie mbv ‘n kunsvagina. Hulle is vir die studie opgeneem en gehuisves in individuele metaboliese hokke. Gedurende fase 1 van die studie is 36 Dorperramme (wat wissel in ouderdom van 11 tot 12 maande) en met ‘n gemiddelde aanvangsliggaamsgewig van 42.0 ± 0.52kg, lukraak aan 3 behandelingsgroepe (n=12 per groep) toegewys. Elke groep het een van 3 eksperimentele diëte, behandelings, (geformuleer op ekwivalente ru-protein, degradeerbare proteïen, kalsium en fosfor basis) ontvang. ‘n Medium-energie (Me) dieet is volgens die NRC-riglyne vir jong, groeiende ramme geformuleer en het as ‘n kontrole dieet gedien. Die metaboliese energie (ME) inhoud van hierdie dieet (Me) is met 15 % verhoog om ‘n hoë-energie (He) dieet daar te stel en met 15 % verminder vir ‘n lae energie (Le) dieet. Die werklike ME vlak vir die Le, Me en He was 6.52, 8.09 en 9.39 MJ/kg onderskeidelik. Die ramme het hierdie diëte en vars water ad libitum vir ‘n 127 dae proefperiode ontvang. Die diere is weekliks geweeg en die GDT, VOV en ME/kg gewigstoename is bepaal en tussen groepe vergelyk. Tydens hierdie tydperk van die proef is ‘n verteerbaarheidsstudie vir ‘n periode van 7 dae gedurende week 14 van die proefperiode uitgevoer, deur 5 diere lukraak van elke behandelingsgroep te kies. Die hoeveelheid voer verskaf en geweier deur elke dier sowel as die faeces uitgeskei, is bepaal. Die chemiese samestelling van die dieet en faeces (ruproteïen, degradeerbare proteïen en energie) is bereken. Semen is mbv ‘n kunsvagina elke 2 weke (3 opeenvolgende dae) gekollekteer vir semenvolume, algehele spermmotiliteit, progressiewe beweging, spermkonsentrasie, % lewendige sperme en % normale sperme geëvalueer. Deur gebruik te maak van ‘n een-stap verdunningsmetode, is die semen met ‘n krioverdunningsmiddel (5 % gliserol) verdun, in 0.25ml plastiese strooitjie verpak en vir 4 ure geëkwilibreer en vervolgens in vloeibare stikstof dampe (-70 ºC) gekriopresiveer. Die semen is ‘n week na bevriesing ontdooi (38 ºC vir 30 sekondes) en geëvalueer vir dieselfde kwantatiewe kenmerke as vir vars semen. Die resultate is vergelyk tussen groepe vir elke kolleksie deur gebruik te maak van die ANOVA vir herhaalde meting prosedures van SAS. Die energievlak van die dieet sowel as die interaksie van die energievlakke, is as onafhanklike veranderlikes in die model gebruik, terwyl die verskillende semenparameters in ag geneem is ook as onafhanklike veranderlikes. Waar die gemiddeldes betekenisvol verskil het, is die Tukey-metode gebruik om die gemiddeldes te vergelyk. Aan die einde van hierdie proefperiode is 6 ramme per groep gekies en by ‘n kommersiële slagpale geslag. Na slagting is die karkaseienskappe (koue karkasgewig, uitslagpersentasie, karkasgradering, karkasgraad, skoueromtrek, boudomtrek, rugvetdikte, oogspierarea, marmering, niervet en skrotale vet) bepaal en tussen groepe vergelyk. Die volgende eienskappe; skrotum (totale gewig, vel gewig, vet en omtrek); testes (volume en gewig) en epididimis (gewig en volume), is bepaal en tussen groepe vergelyk, deur gebruik te maak van die ANOVA prosedures van SAS. Waar die gemiddeldes betekenisvol verskil het, is die Tukey-metode gebruik om die gemiddeldes te vergelyk. Van die onafhanklike veranderlikes wat in die model in ag geneem is, het slegs dieet (ME vlak) ‘n betekenisvolle effek op die parameters gehad. Oor die algemeen, het ‘n toename in dieët-energievlakke ‘n hoër groeitempo, beide tov die karkas en vetneerlegging om die niere en in die skrotum (veral in die nek area, oor die testikulêre keël), tot gevolg gehad. Dit blyk of die energiebehoeftes wat deur die NRC (1985) voorgestel is nie vir vroegryp Dorper vervangingsramslammers gebruik kan word nie omdat die karkasse van die ramme in die He groep (ware ME vlak dieselfde as NRC se aanbevelings) te veel vet aangesit het. Alhoewel betekenisvolle verskille veroorsaak is deur die He dieet op groeitempo, karkaseienskappe sowel as op skrotale and testikulêre eienskappe van Dorper ramme, is geen betekenisvolle effekte in die semen kwantiteit, kwaliteit en krioperservering waargeneem nie. Tydens die volgende 90 dae (fase 2) is al die oorblywende ramme (n=6 per groep) die Le dieet gevoer. Die rede hiervoor was om die situasie te simuleer waar oorvet ramme gekoop word en op lae energie diëte (veld) geplaas word. ‘n Ander doelwit van die studie was om te bepaal of die vetdeponering wat in die skrota akkumuleer, tydens gemiddelde periodes van voedingbeperkings gemobiliseer word en of hierdie voeding veranderings enige verandering in die semeneienskappe van ramme tot gevolg het . Gedurende hierdie fase is semen mbv ‘n KV, elke 3 weke (oor 2 opeenvolgende dae) gekollekteer. Die semen is geëvalueer deur gebruik te maak van dieselfde prosedures as die wat in fase 1 van dié studie beskryf is. Al die ramme is aan die einde van hierdie proeftydperk by ‘n kommersiële slagpale geslag. Na slagting is die karkaseienskappe (koue karkasmassa, uitslagpersentasie, karkasgradering, skoueromtrek, boudomtrek, rug-vetdikte, oogspierarea, marmering, niervet en skrotale vet) bepaal en tussen groepe vergelyk. Die skrotum (totale gewig, vel gewig, vet en omtrek), testes (volume en gewig) en epididimis eienskappe (gewig en volume) is bepaal en tussen groepe vergelyk. Data is statisties geanaliseer deur gebruik te maak van dieselfde prosedures soos beskryf in fase 1. Resultate in die studie wys duidelik dat die skrotale gedeponeerde vet in ramme wat voorheen ‘n He dieet gevoer is, gedurende opvolgende periodes van gemiddelde energie-beperkings gemobiliseer (of ten minste gedeeltelik) word. Hierdie periodes van middelmatige energiebeperkings het egter geen negatiewe effek op semenkwantiteit en kwaliteit veroorsaak nie. Verdere navorsing oor die effek van hoë-energie diëte op daaropvolgende vrugbaarheid in ramme (kort- en langtermyn), sowel as die omkeerbaarheid van vetneerlegging, is geregverdig. Verskillende oud erdomsgroepe, skaaprasse, periodes van behandeling, voerprogramme and ander bestuurspraktyke geassosieer met hoë-energie diëte om die effek van hierdie algemene praktyke op ram vrugbaarheid ten volle te evalueer, moet ook aandag geniet. | af |
| dc.identifier.uri | http://hdl.handle.net/11660/1342 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Dissertation (M.Sc.Agric. (Animal, Wildlife and Grassland Sciences))--University of the Free State, 2006 | en_ZA |
| dc.subject | Dorper (Sheep) -- Reproduction | en_ZA |
| dc.subject | Dorper (Sheep) -- Breeding | en_ZA |
| dc.subject | Dorper (Sheep) -- Feeding and feeds | en_ZA |
| dc.title | Effect of different dietary energy levels on productive and reproductive traits in Dorper rams | en_ZA |
| dc.type | Dissertation | en_ZA |