The use of a cluster analysis in across herd genetic evaluation for beef cattle
To investigate the possibility of a genotype x environment interaction in Bonsmara cattle, a cluster analysis was performed on weaning weight records of 72 811 Bonsmara calves, the progeny of 1 434 sires and 24 186 dams in 35 herds. The following environmental factors were used to classify herds into clusters: solution for herd effects corrected for year-season, sex, age of dam and age at weaning (indicative of the management level in a herd), herd size and average temperature and rainfall. Two different genetic analyses were performed. Breeding values obtained in a univariate analysis were used as basis for comparison to breeding values obtained from a multivariate analysis where weaning weight in each cluster was considered as a separate trait. Direct additive, maternal additive, permanent maternal environment and Herd-Year-Season x Sire (HYSxS) interaction were included as random effects in both analyses. The direct genetic correlations between the clusters varied between 0.51 and 1.00. The low correlation estimates between some of the clusters indicate a possible genotype x environment interaction. Substantial reranking of sires between clusters did occur. However, further research is needed to identify and prioritize variables that can describe the genetics, management and climate of each herd more accurately.
Keywords: Bonsmara cattle, Genotype by environment interaction, weaning weight
South African Journal of Animal Science Vol. 38 (1) 2008: pp. 51-57