Date of this Version
There are significant differences in weaning weight per cow exposed to breeding among F1 cow breed groups. (See "Characterization of Breeds Representing Diverse Biological Types: Reproduction and Maternal Performance of F1 Cows" elsewhere in this report.) These differences are associated with variation among breeds in reproduction, milk production, and growth rate of progeny. Also, there are significant differences among F1 cows in mature weight. Heavier mature weight is associated with more rapid growth rate of progeny, and heavier weights increase output per cow from the production system when cows are sold. However, it also increases the nutrient requirements per cow for maintenance. Thus, it is important to quantify production inputs as well as outputs in order to characterize genetic variation in efficiency of production. The present study was conducted to estimate feed requirements for maintenance and lactation and to estimate biological efficiency (output/input) differences among F1 cows representing diverse biological types.