Genetic parameters for feed intake and efficiency in dry pregnant beef cows
1996
Fan, L.Q. | Wilton, J.W. | Colucci, P.E.
Genetic parameters of feed efficiency and traits relative to feed efficiency for dry pregnant beef cows were estimated from data collected from 1980 to 1988 at the Elora Beef Research Centre, Guelph, Ontario. Measurements of individual feed intake were available for 90 d immediately before calving. Estimates of parameters were obtained using derivative-free restricted maximum likelihood (DFREML), with an individual-animal model with year season, sex of fetus, parity, breeding system, covariate daily backfat change, and genetic and permanent environmental effects. The data included 729 observations, 337 cows, 278 dam-maternal grand dam pairs, and 208 sires of cows. Feed efficiency for pre-calving gain of fetus was calculated as pre-calving gain relative to energy consumed for maintenance and pregnancy, with adjustment of intake for 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 estimated by NRC standards (RFC) or by regression (RFCR). Heritabilities for Hereford alone and total data, respectively, were 0.03 and 0.16 for daily metabolizable energy intake (MEI); 0.20 and 0.44 for metabolic body weight (MBW); 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 for RFC; and 0.03 and 0.22 for RFCR. Genetic and phenotypic correlations indicated a positive association of energy intake with pre-calving fetal gain and weight of cow, although correlations with weight of cow were low. Residual feed consumption for the total data was not genetically associated with MEI or PADG, moderately associated with MBW, and highly negatively associated with FE.
显示更多 [+] 显示较少 [-]