Genetic parameters for growth traits in South African Limousin cattle

Accurate genetic parameters are vital for genetic prediction, selection on breeding values and creation of selection objectives. Consequently, records for birth weight (BW), 200 (WW), 400 (YW) and 600 (FW) day weight were analyzed to obtain heritability estimates. These records originated from Limousin herds with performance data on the South African Limousin Cattle Breeders' Society's database for the period 1980 to 2006. The dataset consisted of 26533 BW, 9756 WW, 6558 YW and 3329 FW records. Log likelihood ratio tests were used to indicate the most suitable model for each trait. Models tested included a herd-year-season by sire interaction (HYSxS) and permanent maternal environmental effect as additional random factors. Single trait analyses yielded direct heritability estimates of 0.09 and 0.19 for BW and WW, respectively while corresponding maternal heritability estimates were 0.05 and 0.12. A strong negative association was found between direct and maternal effects with a genetic correlation of –0.64 and –0.70 for BW and WW, respectively. Direct heritability estimates for YW and FW were 0.16 and 0.24, respectively. Direct genetic correlations of BW with YW and FW were 0.37 and 0.33, respectively. Direct genetic correlations of WW with YW and FW were 0.99 and 0.93, respectively while the correlation between YW and FW was 0.92. Heritability estimates indicate that genetic progress of the above traits will be slower than might be envisaged by some authors, due to lower direct estimates. The strong negative relationship between direct and maternal effects needs to be deliberated when defining selection objectives. Keywords: Limousin cattle; genetic parameters; growth traits South African Journal of Animal Science Vol. 36 (5) 2006: pp.6-

A comparison between single and composite milk samples for the genetic evaluation of milk composition in dairy cattle

A simulation study was carried out to compare the use of single and composite milk samples for the evaluation of milk composition in dairy cattle. The genetic correlation between the two sampling methods was estimated. Results showed a high genetic correlation between the breeding values arrived from composite and single samples. This indicates that the same genes are possibly responsible for both traits, which makes it possible to use a single sample, instead of a composite sample, in predicting breeding values. South African Journal of Animal Science Vol.32(1) 2002: 44-4

Estimates of genetic and environmental (co)variances for live weight and fleece traits in yearling South African Mutton Merino sheep

No Abstract. South African Journal of Animal Science Vol. 34 (1) 2004: pp.37-4

Genetic parameters for growth traits in South African Brahman cattle

Genetic parameters for growth traits in the South African Brahman breed were estimated using ASREML from data records of birth weight (BWT) = 41 509, weaning weight (WWT) = 37 705, yearling weight (YWT) = 22 682 and final weight (FWT) = 13 055 collected between 1985 and 2002. The direct additive contribution to BWT, WWT, YWT and FWT were 0.28, 0.14, 0.14 and 0.18 respectively. The corresponding maternal heritability estimates were 0.11, 0.06, 0.05 and 0.03 respectively. The maternal permanent environmental component due to the dam contributed 3-7% of the total phenotypic variances of the traits under consideration. The corresponding contribution of herd-year-season x sire interaction ranges from 5% to 6%. The genetic correlation between animal effects was -0.36 for BWT. The prospects of improvement of these traits by selection seem possible and contribution of maternal permanent environment due to dam is of considerable importance as maternal effects. South African Journal of Animal Science Supp 2 2004: 44-4

Genetic parameters for growth, reproductive and maternal traits in a multibreed meat sheep population

The genetic parameters for growth, reproductive and maternal traits in a multibreed meat sheep population were estimated by applying the Average Information Restricted Maximum Likelihood method to an animal model. Data from a flock supported by the Programa de Melhoramento Genético de Caprinos e Ovinos de Corte (GENECOC) were used. The traits studied included birth weight (BW), weaning weight (WW), slaughter weight (SW), yearling weight (YW), weight gain from birth to weaning (GBW), weight gain from weaning to slaughter (GWS), weight gain from weaning to yearling (GWY), age at first lambing (AFL), lambing interval (LI), gestation length (GL), lambing date (LD - number of days between the start of breeding season and lambing), litter weight at birth (LWB) and litter weight at weaning (LWW). The direct heritabilities were 0.35, 0.81, 0.65, 0.49, 0.20, 0.15 and 0.39 for BW, WW, SW, YW, GBW, GWS and GWY, respectively, and 0.04, 0.06, 0.10, 0.05, 0.15 and 0.11 for AFL, LI, GL, LD, LWB and LWW, respectively. Positive genetic correlations were observed among body weights. In contrast, there was a negative genetic correlation between GBW and GWS (-0.49) and GBW and GWY (-0.56). Positive genetic correlations were observed between AFL and LI, LI and GL, and LWB and LWW. These results indicate a strong maternal influence in this herd and the presence of sufficient genetic variation to allow mass selection for growth traits. Additive effects were of little importance for reproductive traits, and other strategies are necessary to improve the performance of these animals

Clinical aspects of sentinel node biopsy

Sentinel lymph node (SLN) biopsy requires validation by a backup axillary dissection in a defined series of cases before becoming standard practice, to establish individual and institutional success rates and the frequency of false negative results. At least 90% success in finding the SLN with no more than 5-10% false negative results is a reasonable goal for surgeons and institutions learning the technique. A combination of isotope and dye to map the SLN is probably superior to either method used alone, yet a wide variety of technical variations in the procedure have produced a striking similarity of results. Most breast cancer patients are suitable for SLN biopsy, and the large majority reported to date has had clinical stage T1-2N0 invasive breast cancers. SLN biopsy will play a growing role in patients having prophylactic mastectomy, and in those with 'high-risk' duct carcinoma in situ, microinvasive cancers, T3 disease, and neoadjuvant chemotherapy. SLN biopsy for the first time makes enhanced pathologic analysis of lymph nodes logistically feasible, at once allowing greater staging accuracy and less morbidity than standard methods. Retrospective data suggest that micrometastases identified in this way are prognostically significant, and prospective clinical trials now accruing promise a definitive answer to this issue

Breeding objectives for Holstein cattle in South Africa

Well-defined breeding objectives form the basis of sound genetic improvement programmes. Breeding objectives for Holstein cattle in South Africa were developed in the current study. Economic values were calculated for those economically relevant traits that had adequate bio-economic data, namely milk volume, fat yield, protein yield, liveweight, longevity, calving interval and somatic cell score (SCS). A bio-economic herd model for pasture-based and concentrate-fed systems in South Africa was used to calculate economic values by determining changes in profit arising from an independent unit increase in each trait. Alternative payment systems were used from four major milk buyers in South Africa. Relative economic values, standardized to the value of protein yield, were used to compare the relative importance of traits. Protein yield and longevity consistently had positive economic values and the converse was true for liveweight and calving interval. Economic value for volume was positive or negative, depending on whether the payment system rewarded or ignored volume. Sensitivity analysis showed that economic values were reasonably robust against fluctuations in the cost of feed and price of beef; with the exception of fat yield, whose value became negative when feed price exceeded ZAR 3.50. Generally, protein yield was the most important trait, although volume, longevity and SCS were more important in some situations. Calving interval was the least important trait, its value ranging from 4% to 22% of protein yield, although the model may have underestimated its value. Further work should focus on facilitating the wide adoption of these breeding objectives by industry.Keywords: Butterfat yield, economic value, liveweight, longevity, milk yield, protein yield, relative economic value, somatic cell scor