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Search Results: 1 - 10 of 52 matches for " FWC Neser "
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Genetic parameters for growth traits in South African Limousin cattle
M van Niekerk, FWC Neser
South African Journal of Animal Science , 2006,
Abstract: 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.
The inclusion of herd-year-season by sire interaction in the estimation of genetic parameters in Bonsmara cattle
FWC Neser, KV Konstantinov, GJ Erasmus
South African Journal of Animal Science , 1996,
Abstract: No abstract.
Development of breeding objectives for beef cattle breeding: derivation of economic values: review article
JF Kluyts, FWC Neser, MJ Bradfield
South African Journal of Animal Science , 2003,
Abstract: The purpose of this article is to review the development of breeding objectives in beef cattle breeding and the derivation of economic values. 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: specification of the breeding, production and marketing system, identification of sources of income and expense in commercial herds, determination of biological traits influencing income and expense, derivation of economic values, choice of selection criteria, and estimation of phenotypic and genetic parameters. The modelling methods to derive economic weights can be divided into simulation, dynamic programming and profit functions.
Estimates of genetic and environmental (co)variances for live weight and fleece traits in yearling South African Mutton Merino sheep
SWP Cloete, JB van Wyk, FWC Neser
South African Journal of Animal Science , 2004,
Abstract:
Effect of heat stress on six beef breeds in the Zastron district: The significance of breed, coat colour and coat type
LA Foster, PJ Fourie, FWC Neser
South African Journal of Animal Science , 2010,
Abstract: A study was done to determine which factors had the greatest influence on a heifer’s susceptibility to heat stress. Parameters tested were breed, coat colour, coat score, hide thickness, weight gain, respiration rate and body condition score. The study was conducted in the southeastern Free State. Afrikaner, Bonsmara, Braford, Charolais, Drakensberger and Simmentaler heifers were subjected to a heat tolerance trial. A total of 60 heifers, 10 of each breed were evaluated. Rectal temperature (Tre) was used as a parameter to determine heat stress. The heifers were evaluated on 10 days, at 14:00 during the winter of 2007 and on seventeen days, at 14:00 during the summer of 2007/8 (after 1 h in the sun, no access to shade). In winter a significant difference in rectal temperature Tre between breeds was measured on seven occasions. Phenotypical factors tested for did not affect Tre in winter. In summer significant differences in Tre were measured on 12 occasions between breeds. The following factors had a significant influence on Tre in the following breeds: Afrikaner – hide thickness, Bonsmara – hide thickness, Charolais – coat score.
Genetic parameters for growth traits in South African Brahman cattle
BA Pico, FWC Neser, JB Van Wyk
South African Journal of Animal Science , 2004,
Abstract: 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: 44-46
Genetic parameters for cow weight at calving and at calf weaning in South African Simmental cattle (Short communication)
BJ Crook, FWC Neser, MJ Bradfield
South African Journal of Animal Science , 2010,
Abstract: A study was conducted to compare mature cow weight in the South African Simmental population when defined as the weight of the cow at calving or the weight of the cow at weaning of the calf. Data included in the analysis were 14458 records for cow weight at calving (CWT-C) representing 6534 cows and 18871 records for cow weight at weaning (CWT-W) representing 8395 cows. All cows were born between 1968 and 1996, while all calves were born between 1977 and 1998. The following effects had a significant influence on the traits and were included in the genetic analysis: Cow age in years fitted as a covariate term (linear and quadratic) and contemporary group fitted as a fixed effect. Contemporary group was defined as the unique combination of herd, birth year of calf, month of weighing, breeder-defined management group code for the calf and supplementary feeding code for the cow (for CWT-W). All analyses were done using ASREML, first fitting uni-trait and then bi-variate animal models that made provision for up to four weights per cow. The estimated genetic correlation obtained between the two cow weight traits was 0.95 ± 0.03, with a residual correlation of 0.61 ± 0.02. The heritability estimates for CWT-C and CWT-W from this analysis were 0.29 ± 0.04 and 0.37 ± 0.04, respectively. From a breeding perspective, these results confirm that little benefit is to be gained from weighing cows at calving if cows are to be weighed at weaning. If cow weights are to be recorded for an indication of cow maintenance costs, then weight at weaning is the more reliable and practical measure to record.
A comparison between single and composite milk samples for the genetic evaluation of milk composition in dairy cattle
R Van Dyk, FWC Neser, FH Kanfer
South African Journal of Animal Science , 2002,
Abstract: 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: 44-49
Genetic trends in a South African Mutton Merino nucleus breeding scheme
HQ Gray, FWC Neser, GJ Erasmus, JB van Wyk
South African Journal of Animal Science , 1999,
Abstract:
Preliminary report: Pedigree analysis of the Brangus cattle in South Africa
JW Steyn, FWC Neser, C Hunlun, PC Lubout
South African Journal of Animal Science , 2012,
Abstract: The aim of the study was to investigate some population parameters, including generation interval, inbreeding and effective population size of Brangus cattle in South Africa (SA) to assist in constructing an effective selection programme for the SA Brangus breed. Pedigree analysis can describe the genetic variability and change over time, making it an important tool to be used to assess parameters like generation interval, inbreeding, effective population size and number of animals selected against number born. These traits can be used to make more informed selection decisions in order to maintain a genetically healthy population through a better understanding of the dynamics within the population. A Population Structure- and Pedigree Analysis Report was generated with the PopReport programme from the Institute of Farm Animal Genetics (FLI) with a Brangus datafile containing 65 536 animals. Results were reported for the time period of 1986 to 2008 and the following results were obtained: 3-generation pedigree completeness is at 73.8% for 2008, with an inbreeding coefficient of 1.39% and an annual increase in inbreeding of 0.058%. Weighted generation interval was 5.17 years and the effective population size based on the average inbreeding was 166.7 animals.
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