GENOTYPES OF MILK-PROTEINS AND THEIR EFFE CT ON MILK-PRODUCTION TRAITS

The allelic and genotypic effects of the milk proteins alpha(s1)-Casei n, beta-CN, kappa-Casein and beta-Lactoglobulin on milk production tra its as well as on protein to fat ratio were estimated using informatio n obtained from 1076 cows from the present Black and White population (sample SMR/HF) and 645 cows from the German Black Pied cattle (sample DSR). The results show the same trend in both samples. A positive eff ect of 207 kg and 122 kg milk for A2A2 compared with A1A2 and A1A2 was estimated. The ranking of genotypes in kappa-Casein distinguishes low er in milk yield showing effects for AB>AA>BB with +33>-15>-117kg. Sig nifikant differences of 0.07% fat and 0.06% protein could be proved fo r content traits. The genotype BE of beta-Lactoglobulin showed a posit ive not significant effect of approximately 1.4 kg fat. The effect of beta-Casein genotype A1A1 was significantly better than A1A2 and A2A2 in sample SMR/HF. The beta-Lactoglobulin genotype AA and the A-allele improved not significant the protein to fat ratio as well for content as for yield without appreciable differences in milk yield. The beta-C asein(A2), kappa-Casein(B) and beta-Lactoglobulin(A) additionally impr ove the protein to fat ratio. The estimated genotypic and allelic effe cts of milk proteins on milk production traits are presented.