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Effects of Persistency and Production on the Genetic Parameters of Milk and Fat Yield in Israeli-Holsteins

Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel

ABSTRACT

Herd-years of Israeli-Holsteins were stratified into three groups by two criteria: 1) mean annualized milk yield [365 (total lactations yield/calving interval)] and 2) mean persistency, estimated as the ratio of daily milk production at the 5th mo postpartum to daily production during the postpartum peak period. The latter was taken as an indication of the relative environmental stress on the cow. Primiand multiparous cows were analyzed separately. Genetic parameters were estimated for annualized milk and fat production at each production and persistency group. Heritabilities increased with a rise in production for both primiparous and multiparous cows, but the effect was greater for multiparous cows. Even though persistency and production were correlated, no clear trends were evident for stratification by persistency; thus, a relationship between stress and heritability was not established. Genetic correlations among stratification groups were between .7 and .9 for persistency and betweeen .6 and .86 for production; thus, sire x environmental interaction was greater for production than for persistency stratification. Production in a given year can be used as a criterion for selecting herds to test progeny of young sires in the following year.

This article has been cited by other articles:

				J. I. Weller, E. Ezra, and G. Leitner Genetic analysis of persistency in the israeli holstein population by the multitrait animal model. J Dairy Sci, July 1, 2006; 89(7): 2738 - 2746. [Abstract] [Full Text] [PDF]