19 Heterosis Effects on Pre-Weaning Traits in a Multibreed Beef Cattle Herd in Panama

Abstract The aim of this study was to estimate the influence heterosis and breed percentage on birth weight (BW) weaning (WW) in beef cows a tropical environment. Data from 900 calves 2,843 individuals pedigree, multibreed herd Panama Agricultural Innovation Institute (IDIAP) Gualaca, were used. comprised following genetic groups according their percentage: adapted Brahman (BR), Nellore (Ne), Un define Bos indicus (BI), Guaymi Creole (CR), Senepol (SP) Romosinuano (RS); taurus (BT), Simmental (SM), Angus (A), Red (AR), Limousin (LM), Charolais (CH), Wagyu (Wa), Others (Oth); crossbreeds (cx), Beefmaster (BF), Three cx(F1 x different BT), R1(Backcross BR), R2 (Backcross Composite (combination at least 4 breeds with less than 25% Zebu), Upgrade (87.5% BR 12.5% B1 (62.5% Zebu + 37.5% B2 BT Zebu). A bivariate animal model for BW WW, utilized variance components. Contemporary group defined as year birth. effects sex, season, age dam included categorical fixed effects. Weaning age, degree outcross linear covariates. estimated regression coefficient not significant (P > 0.05), WW 0.072 ± 0.027 kg < 0.05). Lower observed Japanese, B1, while had highest average Heritability found be low (0.14 0.06) moderate (0.26 0.09). proportion variation accounted by maternal permanent environment (0.2 correlation between additive 0.63 0.30, negative, (-0.43 0.37). These results suggested that beneficial but limited effect BW. Additionally, increasing Wa, negatively influenced measurements cattle Panama.