Systematic environmental influences and variances due to direct and maternal effects and trends for yearling weight in cattle

Abstract

Pedigree yearling records from 1021 local Tuli calves born at Matopos Research Station were analyzed for non genetic factors, genetic parameers and trends on the yearling weight. It was found that sre year of brth, sex of calf age of dam had sgnfcant effect (p < 0.01) on a growthtrait. The inconsistency of literature estimates indicated the importance o estmation of environmental factors that affect yearling weight within specific experimental herds and environment. Model incorporating both direct and maternal additive genetic effect, covariance and correlations of direct-maternal and permanent environmental maternal effects was adopted for thestudy Directand maternal heritabity estmates of 0.18 ± 0.001 and 0.04 ± 0001 were observed, respectvely. Direct-maternal genetic correlaton was low andposive, 0.07± 0.012. The regression of average direct breeding values on year was almost zero and the regression of average maternal breeding values on year 0.03 kg/yr. Correction of environmental effects was necessary to increase accuracy for selection of yearling weight in local Tuli cattle. Maternal genetic effects should be included in a model of covariance components estimation at 12 months of age.

Keywords: Non genetic, Direct, Maternal trends, Yearling weight, Growth traits, Tuli cattle