|Martinezvelazquez, G. - UNIV. OF NEBRASKA-LINCOLN|
|Gregory, Keith - RETIRED, ARS COLLABORATOR|
|Van Vleck, Lloyd|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 5, 2001
Publication Date: N/A
Technical Abstract: Data from 12 Bos taurus breeds for scrotal circumference (n = 7,277) and age at puberty (n = 7,580) collected at MARC between 1978 and 1991 were used to estimate heritabilities and genetic correlations. Age at puberty (AP) was defined as the age (days) at first detected ovulatory estrus. Scrotal circumference (SC) was measured (cm) in males at about 358 days of age. Final model for SC included fixed effects of breed (B), age of dam (A), year of birth (Y) and all interactions. Age at measurement of SC was included as a covariate (linear and quadratic) in the model. For AP, final model included fixed effects of B, A, Y, month of birth and all inter- actions. Random effects in the model were direct and maternal genetic, maternal permanent environmental, and residual. A two-trait animal model was used to estimate the (co)variance components using a derivative-free REML algorithm. Heritability estimates were .41 (direct) and .07 (maternal) for SC, and .36 (direct) and .04 (maternal) for AP. Genetic correlations between direct and maternal genetic effects (within trait) were -.12 and -.90 for SC and AP, respectively. Genetic correlations between SC and AP were -.16 (direct), -.30 (maternal), -.12 (direct SC with maternal AP), and .13 (direct AP with maternal SC). Phenotypic variance were 5.90 (SC) and 442.90 (AP). Phenotypic covariance was -3.66. Estimates of direct heritability for SC and AP agree with estimates published by other authors. The estimates of genetic correlations between SC and AP suggest a favorable genetic association. The negative genetic correlations between direct and maternal effects (within trait) and estimates of direct and maternal heritability suggest that selection using SC and AP should consider maternal genetic effects.