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Hereditary Variation in Conception Rate of Holstein-Friesian Cattle¹

Departments of Genetics and Dairy Husbandry, University of Wisconsin, Madison

ABSTRACT

Variation in conception rates (based on birth of a live calf from first insemination to a high-fertility service sire) of 1,406 Holstein females was studied at one or two service periods (1,824 records) in 41 artificially inseminated herds. Fertility did not vary significantly between herds.

Conception rates ranged from 43 to 94% in 27 paternal half-sib groups of heifers (P < 0.05 on an average of 23.4 heifers per half-sib group) and from 33 to 91% in 36 paternal half-sib groups of parous cows (P = 0.05 on an average of 22.7 parous cows per half-sib group).

The heritability of conception rate was estimated from intrasire correlations of paternal half-sib groups to be approximately 8.5%.

A comparison of the records of daughters at both service periods from 22 sires showed a trend toward an interaction between sire and parity of daughters (P 0.07).

The value of selection in improving conception rate is discussed.

¹ Paper No. 827 from the Division of Genetics and the Department of Dairy Husbandry. Published with the approval of the Director of the Agricultural Experiment Station. This work was supported in part by a grant from Wisconsin-Minnesota Cooperative Bull Studs.

² Ralston Purina Fellow.