The heritability of milk productivity and reproduction
1998
Saveli, O. | Kaart, T. (Estonian Agricultural Univ., Tartu (Estonia))
In this research the heritabilities of milk, milk fat and protein yields 305-day, milk fat and protein percentage, somatic cells count, calving interval, service, lactation and dry period and number of inseminations were estimated. The animal recording data from Estonia herd, Kehtna herd, Koigi herd and Palva herd were used. The data were analysed with Harvey program and SAS-program using the sire model. The estimates of heritability with two different methods, Henderson's method 3 and REML method, were calculated. The results show, that the biggest influence on the accuracy of heritability has the number of daughters per sire. If we have big data set and enough daughters per sire, then the heritability is quite stable. For example, the Koigi herd has 470 cows and 16 sires and the heritability is the most stable. In Polva herd we have 619 cows and 93 sires - the number of daughters per sire is too small and the variability between sires is big. This caused big heritabilities for milk fat and protein percentage. The differences between Hendersons method 3 and REML method are not essential. It seems too, that the level of production has no influence on the heritability. The heritabilities of calving interval, service and lactation period and number of inseminations are near to zero. This says that there are not genetic influences on these traits. Only the heritability of dry period was somewhat bigger
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