Population genetic analysis of milk performance traits in German Improved White 2nd communication: Genetic parameters of test day records

The objectives of this study were to estimate genetic parameters for milk performance traits of German Improved White using univariate und multivariate test day animal models. The analysis was based on 12,766 test day records of 1,026 German Improved White with 1,713 lactation records distributed over 80 flocks in Lower Saxony, Saxony and Baden-Wuerttemberg. Milk records were sampled between 1988 and 2002. Tested animals were the progeny of 241 sires and 758 does. Heritabilities estimated with a multivariate test day model with fixed regression were h2 = 0.30, 0.24 and 0.20 for milk, fat and protein yield. For fat and protein content and Somatic Cell Score (SCS) heritabilities were h2 = 0.25, 0.14 and 0.06, respectively. The additive genetic correlations between milk yield and fat as well as protein yield of German Improved White were very high and positive (rg = 0.82 bzw. rg = 0.92). On the contrary, the additive genetic correlations among milk yield and milk contents were negative, with rg = –0.32 for milk fat and rg = –0.34 for milk protein. A moderate additive genetic correlation (rg = 0.48) was estimated between fat and protein content. There were no considerable additive genetic correlations between protein yield and protein content as well as between fat yield and protein content (rg = 0.06 and rg = –0.08). Additive genetic correlations between milk, fat or protein yield and SCS were moderate to high and positive whereas additive genetic correlations between fat or protein content and SCS were moderate to high but negative. The genetic parameters estimated from field test records allow to achieve genetic progress in milk performance traits of German Improved White.

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