Genetic parameters for growth traits in registered Brahman cattle from Mexico

Abstract

IN ORDER TO ESTIMATE AND REPORT GENETIC PARAMETERS, AN UNIVARIATE ANIMAL MODEL WAS ADJUSTED FOR GROWTH TRAITS ON STANDARD AGES OF REGISTERED MEXICAN BRAHMAN CATTLE. THE TRAITS EVALUATED WERE: BIRTH WEIGHT (BWT), WEANING ADJUSTED TO 205 DAYS (WT205), YEARLING (WT365) AND 550 DAYS OF AGE (WT550). THE ADJUSTED UNIVARIATE ANIMAL MODEL INCLUDED THE RANDOM EFFECT OF SIRE, DAM AND RESIDUAL; FIXED EFFECT OF CONTEMPORARY GROUP (HERD, SEX, YEAR AND BIRTH SEASON), AND LINEAL AND QUADRATIC COVARIABLE OF AGE OF DAM. THE GENETIC PARAMETERS WERE ESTIMATED USING MTDFREML SET OF PROGRAMS. A PREVIOUS LIKELIHOOD RATIO TEST WAS CONDUCTED TO SELECT THE BEST MODEL FOR GENETIC PARAMETER ESTIMATION. THEREFORE, THE REPORTED GENETIC PARAMETERS WERE DIRECT AND MATERNAL HERITABILITIES (H2 D AND H2 M, RESPECTIVELY), GENETIC CORRELATION BETWEEN THEM (RDM), AND PROPORTION OF ENVIRONMENTAL RESIDUAL EFFECTS (E2). PHENOTYPIC MEANS FOR BWT, WT205, WT365 AND WT550, WERE 32.2 ± 1.8, 180.7 ± 32.6, 261.6 ± 57.4, AND 352.2 ± 81.3 KG, RESPECTIVELY. THE GENETIC PARAMETER ESTIMATES OF H2 D AND, H2 M, WERE: FOR BWT OF 0.32 AND 0.16, RESPECTIVELY; FOR WT205 OF 0.22 AND 0.08; FOR WT365 OF 0.25 AND 0.20; AND FOR WT550 OF 0.23 Y 0.13, RESPECTIVELY. THE RDM FOR BWT, WT365 AND WT550 WERE, ""0.86, ""0.83 AND ""0.52, RESPECTIVELY. THE PROPORTION OF ENVIRONMENTAL EFFECTS IN RELATION TO PHENOTYPIC VARIANCE E2 FL UCTUATED FROM 0.70 TO 0.74. THE RESULTS SHOWED MODERATE DIRECT EFFECTS FOR ALL THE TRAITS, POTENTIALLY USEFUL FOR GENETIC PROGRESS. THE MATERNAL EFFECTS WERE, APPARENTLY, MORE IMPORTANT FOR THE TRAITS THAT INCLUDED IN THEIR MODEL THE GENETIC COVARIANCE, FOR WHICH IT SHOULD BE TAKEN WITH CAUTION DUE TO A PROBABLE EFFECT OF THE DATA STRUCTURE EVALUATED.