Beef cattle

Variance component estimation of female fertility traits in Afrikaner cows.

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Abstract

In extensive beef production systems, fertility is a fundamental determinant of profitability. Accurate estimation of genetic parameters is necessary to enhance the accuracy of breeding values and to improve the rate of genetic progress. The objective and aim of the study were to obtain genetic parameters for age at first calving (AFC) and calving interval (CI1,2,3) for Afrikaner cattle. The breed once dominated South Africa's beef industry, however, the population declined over time primarily due to concerns regarding low fertility. Reproduction data was was made available by the Afrikaner Cattle Breeders Society and the ARC (Agricultural Research Council). After editing the dataset consisted of 19 226 cow records spanning from 1975 to 2015. Genetic parameters were estimated using the AIREML procedure with univariate and multivariate models in the BLUPF90 family of programs. Each of the calving intervals (1,2,3) were individually investigated as a separate trait. Reproductive performance of Afrikaner cattle Among the effects tested, Herd-Year-Season was the only effect significantly (P < 0.05) effecting AFC. Two alternative models were fitted, with HYS fitted first as a fixed then as a random effect, the second fitted the data better (0.11 ± 0.017). For calving intervals, the same procedure was followed. Permanent environmental effects were not included in the univariate analyses, as each calving interval was analysed separately. A secondary contemporary group (to account for breeding season and ownership changes) was included as a random effect. For each of the three calving intervals, the model where both HYS's were included as a random effect fitted the data better. The results are consistent with those reported in the literature, with estimates of 0.29 ± 0.02 for CI1, 0.07 ± 0.01 for CI2, and 0.10 ± 0.02 for CI3. Multivariate model estimates were 0.06 ± 0.01 for AFC, 0.07 ± 0.01 for CI1, 0.10 ± 0.014 for CI2, and 0.01 ± 0.0001 for CI3. Genetic correlations varied, ranging from 0.31 ± 0.12 between AFC and CI1 to 0.47 ± 0.10 between CI2 and CI3. The genetic correlation between AFC and CI2 was low (0.09 ± 0.12), the correlation between AFC and CI3 was not significant. Moderate genetic correlations were observed among calving intervals, with estimates of 0.34 ± 0.11 between CI1 and CI2 and 0.42 ± 0.11 between CI1 and CI3. Phenotypic and genetic trends were estimated by regressing phenotypic records and mean EBVs, respectively, on year of birth. The phenotypic trend for AFC showed improvement, however the genetic trend for AFC showed the reverse. Phenotypic and genetic trend for ICP showed virtually no improvement. Phenotypic ICP's improved as cows got older possibly as a result of better adaptation to their production environment.

Keywords: 2026

How to Cite:

Goosen, H., Neser, F., Scholtz, M., Cason, E. & MacNeil, M., (2026) “Variance component estimation of female fertility traits in Afrikaner cows.”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286734. doi: https://doi.org/10.31274/wcgalp.24107

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