GENETIC-PARAMETERS FOR FEED-INTAKE AND EFFICIENCY IN DRY PREGNANT BEEF-COWS

Genetic parameters of feed efficiency and traits relative to feed effi ciency for dry pregnant beef cows were estimated from data collected f rom 1980 to 1988 at the flora Beef Research Centre, Guelph, Ontario. M easurements of individual feed intake were available for 90 d immediat ely before calving. Estimates of parameters were obtained using deriva tive-free restricted maximum likelihood (DFREML), with an individual-a nimal model with year-season, sex of fetus, parity, breeding system, c ovariate daily backfat change, and genetic and permanent environmental effects. The data included 729 observations, 337 cows, 278 dam-matern al grand dam pairs, and 208 sires of cows. Feed efficiency for pre-cal ving gain of fetus was calculated as pre-calving gain relative to ener gy consumed for maintenance and pregnancy, with adjustment of intake f or weight change by National Research Council (NRC) standards (FE) or by regression analysis (FER). Residual feed consumption was calculated as energy intake minus energy requirements, with requirements estimat ed by NRC standards (RFC) or by regression (RFCR). Heritabilities for Hereford alone and total data, respectively, were 0.03 and 0.16 for da ily metabolizable energy intake (MEI); 0.20 and 0.44 for metabolic bod y weight (MEW); 0.28 and 0.22 for fetal pre-calving average daily gain (PADG); 0.11 and 0.05 for FE; 0.28 and 0.20 for FER; 0.01 and 0.04 fo r RFC; and 0.03 and 0.22 for RFCR. Genetic and phenotypic correlations indicated a positive association of energy intake with pre-calving fe tal gain and weight of cow, although correlations with weight of cow w ere low. Residual feed consumption for the total data was not genetica lly associated with MEI or PADG, moderately associated with MEW, and h ighly negatively associated with FE.