Relationships between Direct and Maternal Effects on Growth in Herefords: II. Partitioning of Covariance between Relatives

Abstract

PREWEANING growth in mammals is influenced by an individual's genotype for growth (direct genetic effects), by the genotype of the dam for maternal characters and by corresponding environmental effects (Willham, 1963). The importance of each effect independently has long been recognized. The nature of joint effects, however, has come under study more recently. Koch and Clark (1955), Hill (1965) and Deese and Koger (1967) reported genetic antagonisms between direct and maternal effects on preweaning growth in beef cattle. Their observations suggest reevaluation of selection procedures to maximize preweaning growth. A high nutritional environment conducive to rapid early growth of the beef heifer has been reported to be associated with poorer subsequent maternal performance evaluated as progeny weaning weight (see Mangus and Brinks, 1971, for review). This observation suggests altered recommendations for management of replacement heifers. The study reported herein examines direct and maternal genetic and environmental effects on preweaning growth in Hereford cattle.