Parameters and genetic associations of visual scores and weights in Hereford and Braford breeds

Abstract

Additional traits related to function and adaptation are relevant to the proper design of beef cattle breeding programs in tropical production systems. Data from 83,088 Hereford and Braford animals were used to estimate genetic parameters and correlations of visual scores of limb conformation (LC), racial traits (RT), sexual traits (ST), eye pigmentation (EP), navel size (NS) and weights obtained at weaning (WEAN) and yearling (YEAR). Direct heritability for visual scores attributed at weaning and yearling showed moderate values, being, respectively 0.38±0.02 and 0.25±0.02 (LC), 0.25±0.01 and 0.33±0.02 (RT), 0.36±0.02 and 0.24±0.03 (ST), 0.32±0.01 and 0.31±0.02 (EP) and 0.33±0.02 and 0.39±0.02 (NS). For WEAN and YEAR, direct heritability were of 0.15±0.01 and 0.20±0.02, respectively. Positive genetic correlations were estimated between visual scores and WEAN (ranging from 0.33±0.01 to 0.95±0.01) and YEAR (ranging from 0.24±0.11 to 0.80±0.02). The genetic correlations between the same scores attributed at weaning and yearling showed values above 0.94±0.02. Genetic associations estimated between LC, RT and ST ranging from 0.42±0.10 to 0.99±0.01. The EP showed low to moderate genetic correlations with the other evaluated scores. The NS was positively associated with LC, ST and EP, with values ranged from 0.23±0.03 to 0.55±0.06. According to our results, it is possible to obtain genetic gains in adaptation through selection for the studied scores. In addition, the selection for these traits can be performed only in one age, at weaning or yearling. Selection for higher growth should lead to increases in all scores studied. The correlations between adaptation traits favours the selection of animals that present good limb conformation, which fall under the standards demanded by the breed and with desired sexual aspects, besides good eye pigmentation simultaneously. However, it can lead to a higher incidence of lesions on the prepuce, caused by direct contact with the vegetation, due to increase genetic potential in the navel size.