Effects of seven a s2-(3-K-casein haplotypes and individual casein alleles on first lactation milk production traits were estimated for 16 973 Finnish Ayrshire cows by linear multiple regression analysis The haplotypes AA2A, AAjE, AA]B and DA2B were clearly more frequent, whereas haplotypes AAjA, AA2B and AA2E less frequent than expected assuming random combination of casein alleles. Haplotypes AAjA, AA,B and AA,E were strongly associated with low milk and protein yields and high fat-%. Rare haplotype AA2B had a favourable effect on milk and protein yields and AA2A on protein yield. Haplotype AAiB had a strong favourable effect on protein-%. The favourable effect of haplotype AA2B on milk and protein yields and the unfavourable effect of that haplotype on fat-% and protein-% were more pronounced than the cumulative effects of individual as2-, p-, and K-casein alleles on these traits. This indicates that there may be a QTL with alleles closely linked to haplotype AA2B, which have a favourable effect mainly on milk yield, and an unfavourable effect on fat-% and protein-%. 

T. Ikonen, Henk Bovenhuis, M. Ojala, O. Ruottinen

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 25: Lactation; growth and efficiency; meat quality; role of exotic breeds in the tropics; design of village breeding programs; n, , 55–58, 1998
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