|Van Vleck, Lloyd|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/5/2001
Publication Date: N/A
Technical Abstract: Data from 12 Bos taurus breeds for pregnancy rate (P1), calving rate (C1) and weaning rate (W1) at first breeding (n = 7,003), and pregnancy rate (P2), calving rate (C2) and weaning rate (W2) combining second to tenth ages at breeding (n = 15,739) collected at MARC between 1979 and 1990 were used to estimate heritabilities and genetic correlations. Pregnancy (calv- -ing or weaning) rate was one if the female conceived (calved or weaned) a calf given exposure during preceding breeding season and zero, otherwise. Final model for P1, C1 and W1 included fixed effects of breed (B) and year of breeding (Y) subclass. For P2, C2 and W2, the final model included fixed effects of B, Y, age at breeding (yr) and all interactions. Random effects in model were direct and maternal genetic, maternal permanent environmental, and residual. Unadjusted means (SD) were .75 (.43), .71 (.44), .59 (.49), .84 (.35), .81 (.38) and .76 (.42) for P1, C1, W1, P2, C2 2and W2, respectively. A single trait animal model were used to estimate the (co)variance components using a derivative-free REML algorithm. Heritability estimates were .15 (.03) (direct) and .02 (.01) (maternal) for P1, .15 (.03) (direct) and .03 (.01) (maternal) for C1 and .11 (.02) (direct) and .00 (.01) (maternal) for W1. Direct and maternal heritability estimates for P2, C2 and W2 were .00 to .02. Genetic correlations between direct and maternal genetic effects (within trait) were -.83 (.71) and -.68 (.55) for P1 and C1, respectively. Heritability estimates indicate that management is important for these traits, especially after first breeding season. Estimates of genetic correlations and direct and maternal heritability suggest unfavorable genetic associations between direct and maternal genetic effects for P1 and C1.