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Hough D.,Stellenbosch University | Cloete S.W.P.,Stellenbosch University | Cloete S.W.P.,Institute for Animal Production Elsenburg | Storbeck K.,Stellenbosch University | And 2 more authors.
Journal of Animal Science | Year: 2013

In commercial production systems, the full expression of the genetic potential of an animal is limited by its intrinsic and extrinsic environment. It is therefore necessary to include robustness as a breeding goal because robustness is defined as the ability of an animal to express a high production potential in a wide variety of environmental conditions. The ability of mammals to produce sufficient cortisol on stimulation of the hypothalamic-pituitary-adrenal (HPA) axis is vital in its adaptation to stress. The biosynthesis of cortisol is dependent on the enzymatic activity of the microsomal enzyme, cytochrome P450 17α-hydroxylase/17,20- lyase (CYP17). Two isoforms for sheep (Ovis aries) CYP17, previously identified in 2 independent studies, differ by 2 nucleotides, resulting in 2 AA differences (Ser210Gly and Tyr464Asn). The present study investigates the effect of these differences on cortisol production as a function of the HPA axis activity by comparing the catalytic activities of these isoforms. The activities of the CYP17 isoforms were compared by expressing the enzymes in vitro. The kinetic constants, Vmax and Km, which were determined for pregnenolone and progesterone (in the absence of cytochrome b5), showed no significant difference (P > 0.05) between the CYP17 isoforms. In contrast, a time course of the metabolism of pregnenolone, 17-hydroxypregnenolone, and progesterone, assayed in the presence and absence of ovine cytochrome b5 overexpression, showed significant differences (P < 0.05) between the isoforms. Wild-type 1 CYP17 (WT1, GenBank accession number L40335) yielded more cortisol precursors than wild-type 2 (WT2, GenBank accession number AF251388). Sitedirected mutagenesis indicated that a tyrosine residue at position 464 of WT1 increased the 17α-hydroxylation of progesterone compared with an asparagine residue at that position of WT2. In a subsequent insulin-induced hypoglycemic stress test, the presence of WT1 resulted in a greater cortisol output from the sheep adrenal than the presence of WT2, as homozygous WT1/WT1 sheep produced more cortisol than heterozygous WT1/WT2 sheep. The SNP located within the WT1 allele may therefore have a potential application in marker-assisted selection of sheep exhibiting a greater release of cortisol from the adrenal gland in response to stressors. © 2013 American Society of Animal Science. All rights reserved.


Scholtz A.J.,Institute for Animal Production Elsenburg | Scholtz A.J.,University of the Free State | Cloete S.W.P.,Institute for Animal Production Elsenburg | Cloete S.W.P.,Stellenbosch University | And 3 more authors.
Animal Production Science | Year: 2010

Divergent selection resulted in Merino lines that differ markedly for reproduction. These lines were selected from the same base population from 1986 to 2009. Selection was initially based on maternal ranking values for reproduction in both ewe and ram progeny. The maternal ranking scores were augmented by breeding values from a single-trait repeatability model since 2003. The site and severity of flystrike were recorded for mature breeding ewes in the flock from 2007 to 2009. The following details were captured: animal number, site of the strike (body or breech) and the severity of the strike (1 ≤ mild to 5 ≤ severe). Breech strikes amounted to 92.1% of all strikes and this trend was consistent across years. High-line ewes were less likely (P 0.05) than low-line ewes to be suffering from breech strike. Ewes that suffered from breech strike during a reference year were more likely to be struck again during subsequent years, when compared with contemporaries not affected by breech strike in the reference year. When breech strike and body strike were assessed in a joint preliminary analysis, it seemed that body strike was generally more severe when diagnosed than breech strike. It was concluded that Merino sheep selected for improved reproduction for 20 years were less likely to be affected by breech strike than contemporaries selected for low reproduction. © CSIRO 2010.


Cloete J.J.E.,Elsenburg Agricultural Training Institute | Hoffman L.C.,Stellenbosch University | Claasen B.,University of Namibia | Cloete S.W.P.,Institute for Animal Production Elsenburg
Livestock Research for Rural Development | Year: 2012

An investigation on the effect of production system on growth rate, carcass characteristics and carcass composition of Dorper lambs was carried out under South African conditions. The study involved sixty lambs which were divided into two production/feeding groups (feedlot (FL) vs. free-range (FR)) at weaning. Each group consisted of 10 lambs from three gender classes (ewes, rams and castrates). The FL-lambs were fed a commercial pelleted ration while the FR-group grazed natural pastures. The production system x gender interaction indicated that male lambs (castrates and rams) grew twice as fast as ewes under FL-conditions. Gender groups were less pronounced in FR-lambs. FL-lambs produced heavier carcasses, higher dressing percentages and greater carcass fatness levels than FR-lambs. Ram lambs attained heavier slaughter weights and produced heavier carcasses than ewe lambs with castrates being intermediate. Production system did not have an effect on intramuscular lipid concentration, barring a tendency in the Biceps femoris muscle. It was concluded that the FL-diets were generally associated with better lamb growth rates, greater carcass fatness and an improved dressing percentage. Although animal performance was generally improved in the more intensive FL-system, it was also concluded that discerning consumers will likely prefer the more natural (and therefore more ethically acceptable) FR-meat.


Bonato M.,Stellenbosch University | Rybnik P.K.,Polish Academy of Sciences | Malecki I.A.,University of Western Australia | Cornwallis C.K.,University of Oxford | And 2 more authors.
South African Journal of Animal Sciences | Year: 2010

This study is part of an ongoing project on artificial insemination in ostriches. The physical output of neat semen from four ostrich males was investigated and the effect of reconstituting semen with: 1) seminal plasma of the same male (SPS); 2) seminal plasma of another male (SPD), and 3) Dulbecco's Modified Eagles Medium (DMEM). Semen was collected daily from one or two pairs of males using the dummy female method, each pair being replicated twice. Spermatozoa viability in neat semen, SPS, SPD and DMEM was assessed using nigrosin-eosin staining and the proportions of live normal, live abnormal and dead sperm were determined. Semen volume (mean ± SE) was 1.27 ± 0.13 mL, the concentration of spermatozoa 3.68 ± 0.17 x 109 /mL and the number of spermatozoa 4.92 ± 0.64 x 109 /ejaculate. Furthermore, the live normal, live abnormal and dead spermatozoa in the neat semen were 61.2 ± 4.5%, 21.2 ± 2.7% and 17.7 ± 4.3% respectively. The ejaculate volume and the number of dead spermatozoa were not affected by collection time. However, the number of live abnormal spermatozoa increased through the day causing a reduction in live normal spermatozoa. Furthermore, re-suspending spermatozoa in DMEM reduced the number of live normal (31.4 ± 4.6%) and live abnormal spermatozoa (11.0 ± 2.7%) and increased the number of dead spermatozoa (57.6 ± 4.4%). In contrast, numbers of live spermatozoa were higher when suspended in seminal plasma and similar in SPS (53.9 ± 4.6%) and SPD (50.7 ± 4.6%). These are the first crucial steps to determining the optimum semen collection time and to improving the viability of diluted spermatozoa. © South African Society for Animal Science.


Cloete S.W.P.,Stellenbosch University | Cloete S.W.P.,Institute for Animal Production Elsenburg | Brand T.S.,Stellenbosch University | Brand T.S.,Institute for Animal Production Elsenburg | And 8 more authors.
World's Poultry Science Journal | Year: 2012

This paper summarises research on farmed ratites and their industries over the past 100 years. Commercial ratite products include meat, skins, feathers and oil. Research on ratites has attempted to enhance the quantity and quality of these products by focusing on the disciplines of breeding and genetics, reproduction and incubation, assisted reproduction, nutrition and animal welfare. Advances in these disciplines are discussed, and directions for future research are provided. © 2012 World's Poultry Science Association.


Bonato M.,Stellenbosch University | Cornwallis C.K.,Lund University | Malecki I.A.,University of Western Australia | Rybnik-Trzaskowska P.K.,Warsaw University of Life Sciences | And 2 more authors.
Animal Reproduction Science | Year: 2012

As the chemical environment of semen diluents can have a profound effect on sperm quality, we examined the effect of temperature and pH on the motility and viability of sperm in the ostrich. Semen was collected from four males, each male being replicated three times. Ejaculates were diluted and incubated for 10. min at 20. °C and 40. °C in four different buffers, temperature adjusted at pH 6, 7, 8 and 9 respectively. Average path velocity (VAP), curvilinear velocity (VCL), straight-line velocity (VSL), linearity (LIN), beat cross frequency (BCF) and amplitude of lateral displacement (ALH) were then recorded for each sample using CASA. The viability of sperm was assessed using nigrosin-eosin staining. Sperm incubated at 40. °C had higher motility parameters, except for ALH. At 40. °C, VAP, VSL and LIN increased with pH while VCL, BCF and ALH were higher for lower pHs. The viability of sperm was not affected by temperature but decreased at pH values. >. 7. A pH in the neutral range appeared to yield higher quality sperm after in vitro storage at 20. °C. However, the effect of different pH levels and temperatures on sperm longevity needs to be investigated further to develop viable ostrich specific diluents. © 2012 Elsevier B.V..


Zishiri O.T.,Stellenbosch University | Cloete S.W.P.,Stellenbosch University | Cloete S.W.P.,Institute for Animal Production Elsenburg | Olivier J.J.,ARC | Dzama K.,Stellenbosch University
South African Journal of Animal Sciences | Year: 2010

Genetic trends were constructed for early growth traits in the Dormer and Ile de France terminal sire sheep breeds. The traits that were considered were birth weight, pre-weaning weight, weaning weight and post-weaning weight. However, pre-weaning weights were only available for the Ile de France breed and post-weaning weights were only available for the Dormer breed. Regressions of average annual breeding values on birth year indicated significant genetic gains in all early growth traits during the evaluation period. The average predicted direct breeding value of birth weight decreased by 0.055% per annum whereas weaning weight increased by 0.12% per annum and post-weaning weight improved by 0.32% per annum in the Dormer breed. The Ile de France registered an undesirable increase in the predicted direct breeding value of birth weight which amounted to 0.025% per annum. Predicted direct breeding values for pre-weaning weight increased at an annual rate of 0.23% and that of weaning weight by 1.21% per annum. Although adequate genetic variation for substantial genetic progress was available, only modest rates of progress were attained for all the traits in both breeds. The only possible exception was weaning weight in the Ile de France breed, which was improved at > 1% per annum. At least all changes were in the desired direction, barring the direct genetic trend for birth weight in the Ile de France breed. Breeders should be encouraged to record data consistently, as one of the major shortcomings in the data for both breeds were a lack of continuity in the submission of data to the NSIS. More informative analyses ought to be feasible if this requisite is met. © South African Society for Animal Science.


Bonato M.,Stellenbosch University | Rybnik P.K.,University of Western Australia | Malecki I.A.,University of Western Australia | Cornwallis C.K.,University of Oxford | And 2 more authors.
Animal Reproduction Science | Year: 2011

The success of an artificial insemination program in ostriches is highly dependent on the yield of viable semen. We, therefore, tested how semen output is affected by three different collection frequencies: once every 2. d (48. h interval), daily (24. h interval), and twice a day (6. h interval). Ejaculates were collected from seven male ostriches (aged 2-4 years) for 10 consecutive days using the dummy female method. We assessed semen characteristics (sperm motility, volume, concentration, number of sperm per ejaculate and sperm viability) and male libido (the delay between the presentation of the dummy and ejaculation, and the willingness to mount the dummy). The total daily output of semen and the number of sperm were greater at the 6. h collection interval than at the 24. h or 48. h interval while sperm motility and viability were not affected. At the 6. h interval, the number of live normal sperm increased over the treatment period while the number of live abnormal sperm was reduced. Furthermore, the time that males took to mount the dummy and their willingness to copulate with the dummy were unaffected by collection frequency. Across males we observed great individual variation in both semen characteristics and libido suggesting there is the potential to increase the efficiency of semen collection by selecting superior males. These results indicate not only that two collections per day yield maximum semen output and may improve semen viability, but also that quantifying variation between males may help further increase semen collection efficiency. © 2011 Elsevier B.V.


Wang M.D.,Stellenbosch University | Cloete S.W.P.,Stellenbosch University | Cloete S.W.P.,Institute for Animal Production Elsenburg | Dzama K.,Stellenbosch University | And 3 more authors.
South African Journal of Animal Sciences | Year: 2012

The effects of human imprinting and foster parenting by adult ostriches on the survival and growth performance of ostrich chicks were compared to conventional chick-rearing practices in two separate experiments. In the first experiment, the growth rate and survival of chicks imprinted onto humans were compared with those of chicks reared by adult foster parents (n = 100 for both groups). Survival is expressed as proportions, while weights were measured in kg. Treatment did not affect chick survival to 3 weeks (0.90 for imprinted chicks vs. 0.89 for foster chicks), or from 4 to 12 weeks (0.86 vs. 0.83, respectively). Chick weight was not significantly different between groups at 4 weeks, but at older ages, those chicks reared by foster parents consistently outperformed imprinted chicks (means ± SEs being 12.8 ± 0.4 vs. 8.2 ± 0.4 kg at 9 weeks, 37.1 ± 0.8 vs. 19.9 ± 0.80 kg at 18 weeks and 46.2 ± 1.1 vs. 28.6 ± 1.2 kg at 22 weeks). In the second experiment, the treatments consisted of a human-imprinted group of chicks and a group subjected to conventional rearing methods (as customary on the research farm). Chick survival to four weeks was significantly higher for imprinted chicks than for conventionally reared chicks (0.97 vs. 0.84), although chick weight was independent of treatment at 4 weeks (6.27 ± 0.16 kg for the imprinted group vs. 6.18 ± 0.17 kg for the conventional group) and at 15 weeks (respectively 16.5 ± 0.68 vs. 15.2 ± 0.70 kg). Overall, chicks reared by foster parents were heavier than human-imprinted chicks, while early survival of imprinted chicks was better than that of chicks reared by conventional handling. Imprinting thus affected survival of ostrich chicks relative to conventional rearing practices. Because most ostrich chicks are reared with conventional methods, the present study indicates that improvements can be made by adopting alternative approaches. Further studies are needed to ascertain how foster parenting and imprinting may be utilized to optimize chick performance, including the long-term consequences of these practices.


Brand T.S.,Institute for Animal Production Elsenburg | Brand T.S.,Nelson Mandela Metropolitan University | Jordaan J.W.,Nelson Mandela Metropolitan University | Bhiya C.S.,Nelson Mandela Metropolitan University | Aucamp B.B.,Institute for Animal Production Elsenburg
British Poultry Science | Year: 2010

1. The effects of different slaughter ages and sex on the yield and quality of economically important end-products of slaughtered ostriches was examined to determine the most economic slaughter age for growing/finishing ostriches. Two batches of 4- and 6-month-old ostriches were assigned to 10 treatment groups and fed ad libitum up to slaughter ages of 8.5, 10.5, 12.5, 14.5 and 16.5 months. Slaughter weight, cold carcase yield, skin surface area, dry skin grade, feather yield and feed intake of ostriches were measured for each age. 2. Cold carcase yields and total feather yields of males were higher than females but yields of other products were similar. 3. Slaughter weight, cold carcase yield, skin surface area, dry skin grade, feather yield and feed intake increased with age with significant differences between most age groups. Cold carcase weight increased by approximately 2.2kg and skin surface area increased by 3.1 dm3 with each additional month of growth but the quality (grade) of skins and the proportion of first grade skins decreased with increasing age. This, together with an increase in feed intake associated with age to slaughtering should be taken into account when determining the optimal slaughter age. 4. The set of biological variables established in this study can be used to determine the most economical slaughter age under varying market conditions. © 2010 British Poultry Science Ltd.

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