GENETIC-PARAMETERS FOR FEED-INTAKE AND EFFICIENCY IN LACTATING BEEF-COWS

Genetic parameters of feed intake and efficiency and production traits for lactating beef cows were estimated from data collected from 1980 to 1988 at the flora Beef Research Centre, Guelph, Ontario. Estimates were obtained using restricted maximum likelihood (REML) with an indiv idual animal model with year-season-treatment, sex of calf, parity, br eeding system, covariate daily change of backfat depth and direct gene tic and permanent environmental effects. The data included 1174 observ ations, 511 cows, 369 dam-maternal grand dam pairs and 245 sires of co ws. Feed efficiency for milk was calculated as milk yield relative to energy consumed for milk and maintenance and residual feed consumption as estimated energy intake minus energy requirements as estimated by the National Research Council. Heritabilities for Herefords alone and total data, respectively, were estimated to be 0.02 and 0.11 for cow's daily ME intake (MEI), 0.26 and 0.26 for daily milk yield (DMY), 0.45 and 0.33 for milk fat percentage (MFP), 0.29 and 0.40 for metabolic b ody weight (MEW), 0.21 and 0.10 for calf weaning weight as a proportio n of cow weight at weaning (PPW), 0.18 and 0.11 for feed efficiency fo r milk (FE), and 0.23 and 0.03 for residual feed consumption (RFC). Ge netic correlations of output (DMY) and input (MEI) were 0.31 for Heref ord and 0.75 for the total data. Genetic correlations of RFC with both output (DMY) and input (MEI) were low. Genetically, PPW was positivel y associated with FE and DMY and negatively associated with MEW.