Genetic analysis of days to calving in Nelore beef cattle

A Nelore population data were analyzed to estimate genetic parameters for days to calving (DC) and verify the possibility of using it as a selection criterion. There were 49 698 calving observations from 36 196 females. Data were analyzed using a single-trait animal model. The fixed effects were contemporary groups, calf sex and age of dam at joining as a covariable. The contemporary groups were composed of farm, year, season and handling group at joining and mating type (a mating group with multiple sires, a mating group with one sire or artificial insemination). The inclusion of permanent environmental effects of animals did not increase the likelihood function significantly. Heritability estimate was 0.090 ± 0.006, indicating that DC is strongly influenced by the environment

Genetic parameters for post-weaning visual scores and reproductive traits in Suffolk sheep

The aim of this study was to estimate the coefficients of heritability and genetic correlations among visual scores (conformation, CPW; precocity, PPW; musculature, MPW) and reproductive traits: age at first lambing (AFL) and scrotal circumference (SC) evaluated at 180 days of age in Suffolk lambs. In the statistical model only the additive genetic effect was considered as random effect. The heritability estimates by univariate analyses for CPW, PPW, MPW, AFL and SC were 0.08, 0.12, 0.09, 0.20 and 0.22, respectively. The genetic correlations among AFL and CPW, PPW, MPW were -0.26, 0.19, and 0.08, respectively. The genetic correlation among SC and CPW, PPW, MPW were, respectively, 0.54, 0.88 and 0.86, and between AFL and SC was 0.26. The direct selection for conformation, precocity and musculature at 180 days of age and age at first lambing will provide slow genetic progress due to low heritability estimates. It is possible to obtain genetic gain in sexual precocity through selection on scrotal circumference in Suffolk rams. The favorable genetic correlation among visual scores and SC and between CPW and AFL, indicated the possibility to gain in genetic progress for reproductive traits through indirect selection of the visual scores in Suffolk sheep