Casein polymorphism and relation between milk production traits

The relation between milk yield and fat yield on one side and far percentag e and protein percentage on the other Is partly described Dy strong negativ e correlation coefficients. An influence of casein polymorphism on this tra it relation could be proved. The estimated direct effects of markers and th e results of segregation and linkage analysis are considered in this connec tion. One or more than one QTL exist on chromosome 6 linked to the casein s uper locus that affects yield traits as well as percentage traits. It has b een shown that the casein genotypes (CN) contribute to the correlation betw een yield traits and percentages of protein and fat as well. There are clea r suggestions to different directions of casein genotypic influence for fat yield; protein yield aid percentages of protein and far according to the r esults from estimated direct marker effects and partly also from linkage an alysis. Significant evidence for linkage was obtained regarding fat percent age kappa-casein (LOD score 3.03). The estimated genotypic effects show a p ositive influence of beta-CNA2 and kappa-CNA On milk yield, far yield and p rotein yield and a simultaneous negative effect on fat percentage and prote in percentage.