Abstract The objectives this paper were to estimate genetic parameters genetic phenotypic trends of birth weight (BWT) weights adjusted to 205 (WT205) 365 (WT365) 550 (P550) days of age of beef buffaloes born from 1985 to 2003 in Brazil. For BWT WT205 the model included direct maternal genetic maternal environment as random effects contemporary genetic groups as fixed effects. For WT365 WT550 the same model was used except without direct maternal maternal environmental effects. The genetic phenotypic trends were estimated by regression of means of dependent variables on birth year of animals. Regressions were obtained by using two methodologies: 1) linear regression; 2) non-parametric splined regression. The direct heritability estimates were 0.09 0.45 0.46 0.58 for BWT WT205 WT365 WT550 respectively. The direct genetic trends from linear regression were 0.01 0.23 0.58 1.40 kg per year for PN WT205 WT365 WT550 respectively (P<0.001 for all). Phenotypic trends were strongly positive while genetic trends were consistently positive but small. Genetic parameters indicate potential for increased rate of genetic change with full implementation of genetic improvement programs.
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