A Study of the Inheritance of Breeding Efficiency in the Beltsville Dairy Herd

Abstract

ConclusionsThe results of this investigation indicate that the intraherd repeatability and heritability values of breeding efficiency in dairy cattle are low. When the number of services required for conception, the number of days from first service to conception, or the regularity of the occurrence of estrus are used as measures of breeding efficiency, selection for improvement in breeding efficiency will not be very effective. Dairy cattle breeders can make greater progress in the improvement of the genetic merit of their herds by practicing selection for other traits of economic importance, such as high milk production, which has much higher repeatability and heritability values. Environmental factors that appear to be of relatively minor importance as the causes of variation in breeding performance are age of the cow, season of the year, and time trends. A large body of accurate and complete data, based on a herd where adequate controls are maintained purely for the purpose of investigating breeding performance, is needed in order to obtain a more exact picture of the relative importance of these environmental factors.