Effects of composite P-K-casein genotypes and P-lactoglobulin genotypes on reproduction traits were estimated for 17059 Finnish Ayrshire (FAy) heifers and 17869 FAy first lactation cows using an animal model. No significant effects of composite P-K-casein genotypes on reproduction traits of Fay heifers were observed. P-lactoglobulin genotypes had statistically significant effect on heifers’ age at first insemination, age at conception and age at calving. Heifers with AA genotype were 3 to 6 days younger at first insemination, conception and calving than heifers with p-lactoglobulin BB genotype. Composite p-K-casein genotypes and P-lactoglobulin genotypes had, in general, no significant effect on reproduction traits of Fay first lactation cows. The effect of composite P-K-casein genotypes on interval between calving and first service in first lactation was statistically significant, but most of the differences between composite P-K-casein genotypes were negligible in this trait. It can be concluded, that milk protein genotypes had no effects on reproduction traits of heifers or first lactation cows, or the effects were small in practice. Thus, the possible selection for milk protein genes would hardly have any noticeable impact on reproduction traits in dairy cows.

O. Ruottinen, T. Ikonen, M. Ojala

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 23: Opening: plenary; technology; transfer; beef cattle; dairy cattle; pigs., , 443–446, 1998
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