Association Between SSCP Haplotypes at the Bovine Growth Hormone Gene and Milk Protein Percentage

The bovine Growth Hormone gene (bGH) is an attractive candidate gene for milk production in cattle. Single-strand conformation polymorphisms at bGH were identified and used to define haplotype configurations at this gene in the Israeli Holstein dairy cattle population (Bos taurus) and in the parent animals of the International Bovine Reference Family Panel (a collection of B. taurus and B. indicus crosses). B. taurus and B. indicus haplotypes at the bGH gene differed qualitatively, confirming the previously proposed long evolutionary separation of these cattle subraces. Only a small number of bGH haplotypes were present in the Israel Holstein population. One of the haplotypes, apparently of B. indicus origin, was found to have a highly significant positive effect on milk protein percentage. This illustrates the utility of the haplotype approach for uncovering candidate gene involvement in quantitative genetic variation in agricultural populations. The strong effect of an indicine haplotype in a taurine background raises the possibility that indicine alleles at other candidate genes may comprise a genetic resource for improvement of taurine populations. It is proposed that haplotype analysis may be a useful adjunct to measures of genetic distance for evaluating rare breeds with respect to gene conservation.