Associations between casein haplotypes and milk production traits of Swissbrown cattle

Effects of casein haplotypes and beta-lactoglobulin (LG) genotypes on milk protein fractions and on daughter yield deviations for milk performance tra its were estimated from a daughter design. Offspring of seven Swiss Brown s ires with the haplotypes B-A-B-A and B-A-B-B for alpha(s1)-, alpha(s2)-, be ta-, and kappa-caseins were selected. The milk of daughter groups with pate rnal haplotype B-A-B-A was associated with lower casein content and higher whey protein content compared with B-A-B-B. Because of these contrary effec ts, the true protein content was not affected by the paternal haplotypes. T he effects of maternal haplotypes were significant on true protein and case in content but not on whey protein content. The beta-LG genotypes had highl y significant effects on casein and whey protein content. The effect of bet a-LG BE was positive on casein and negative on whey protein content compare d with beta-LG AA; the effect of beta-LG AB was intermediate. No significan t effects of paternal haplotypes were found for daughter yield deviation on kilograms of milk, fat, and protein or percentages of fat and protein. The effects of the beta-LG genotypes were, independent of the parental haploty pes, close to significant on daughter yield deviation for percentage of pro tein. The beta-LG BE tended to be associated with a higher protein content compared with beta-LG AA. The effects for beta-LG genotypes showed additive gene effects. The analysis of paternal haplotypes within sires revealed a contrary effect of haplotypes for two of the seven sires for casein content . The paternal haplotypes within sire showed, although not significant, tha t haplotypes of the two sires had a contrary effect on daughter yield devia tion for percentage of protein as well.