Extended Cow Liveweight Modelling for Beef Cattle Breeding Objectives

Abstract

An extended procedure is described for modelling cow liveweight change over the production year for valuing cow liveweight in breeding objectives. The pattern of change, before and after trait change, is able to be approximated from breeder-described variables for any production system. Examination of seven datasets showed cow liveweight changes systematically over age in many herds and breeds. Analyses showed liveweight loss from pre-calving to mating and cow liveweight at mating both change in proportion to the liveweight of the cow pre-calving. Differences in cow liveweight pre-calving are thus larger than are the differences at mating, which affects feed costs in valuing cow liveweight at mating. Adoption of the procedure will increase the precision with which feed cost is associated with cow liveweight in beef cattle breeding objectives.