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Predictability of Breeding Efficiency in Dairy Cattle from rheir Previous Conception Rate and from their Heredity¹

University of Nebraska

ABSTRACT

The breeding efficiency from artificial insemination over an eight-year period in the University of Nebraska dairy herd was analyzed. The summer and late summer months required more services per conception than did the months during the other seasons of the year. August was high with 2.24 services per conception and this is highly significant.

Results indicated that it was not possible to predict from the breeding efficiency of the previous year the number of services required for subsequent conceptions. The services required for conception in virgin heifers did not give any indication as to the number of services required for the following conception, for the average number of services required per conception throughout the lifetime of the individual, and no indication as to the number of services required for the first conception in her daughters. An analysis of the breeding histories for the cows sold as sterile showed that their previous breeding records gave no indication that sterility would follow.

Daughter-dam comparisons made for the average number of services required for all conceptions throughout the lifetime of the individual indicated that it is not possible to predict the breeding efficiency of daughters from the breeding records of their dams. However, when the services required per conception were tabulated by cow families, it was found that among twenty families there was one with very low fertility and two with extremely high fertility. Analysis of the breeding records for the daugh-ters of nineteen bulls revealed one with daughters that required a highly significant number of services per conception and another sire that very closely approached this level.

¹ Published with the approval of the Director as Paper No. 375, Journal Series, Nebraska Agricultural Experiment Station.

² Now at Cornell University, Ithaca, New York.