Age of dam and sex of calf adjustments and genetic parameters for gestation length in Charolais cattle

摘要: To estimate adjustment factors and genetic parameters for gestation length (GES), AI calving date records (n = 40,356) were extracted from the Canadian Charolais Association field database. The average time to was 285.2 d (SD 4.49 d) ranged 274 296 d. Fixed effects sex of calf, age dam (2, 3, 4, 5 10, ≥11 yr), contemporary group (year birth x herd origin). Variance components estimated using REML 4 animal models 84,332) containing 0 3 random maternal effects. Model 1 (M1) contained only direct 2 (M2) G1 plus with covariance constrained zero, model (M3) G2 without constraint. (M4) extended G3 include a permanent environmental effect. Direct heritability estimates high similar among all (0.61 0.64), low, ranging 0.01 0.09 (M3). Likelihood ratio tests parameter suggested that M4 most appropriate (P < 0.05) model. With M4, phenotypic variance (18.35 ) partitioned into genetic, (h 0.64 ± 0.04, h m 0.07 0.01, r d,m -0.37 0.06, c 0.03 respectively). Linear contrasts used bull calves gestated 1.26 longer 0.02) than heifers, adjustments mature equivalent (5 10 yr old) 1.49 0.01), 0.56 0.33 -0.24 0.14) GES born 2-, 3-, 4-, ≥11-yr-old cows, respectively. Bivariate adjusted 205-d weaning weights, postweaning gain. positively correlated weight (BWT; 0.34 0.04) but negatively BWT (-0.20 0.07). Maternal had negative correlation (-0.15 positive (0.62 Generally, near-zero correlations weights. Results suggest important associations exist BWT, gain less important.