Alternative contemporary group structure to maximize the use of field records: Application to growth traits of composite beef cattle

The objective of the present study was to define an alternative contemporary group structure that would permit an increase in the number of records to be included in genetic evaluations with minimal bias. For this purpose, using different criteria as goodness of fit measured by percentages of squared bias, correlations between predicted and observed records, residual variances, genetic trends, rank correlations, and a practical situation of genetic evaluation, an animal model with standard contemporary group structure was compared with a model with alternative contemporary group structure including weaning management group (WMG) as an additional uncorrelated random effect for postweaning growth traits of composite beef cattle. The present study showed that the inclusion of WMG as a random effect in the statistical model for postweaning growth traits has only a small impact on animal ranking and a small or no impact on the estimation of genetic parameters and genetic trends. On the other hand, this approach leads to an important increase in the number of records available for the prediction of genetic merit with minimal or even no bias. Therefore, the model proposed here can be recommended to overcome problems related to loss of data of model with standard contemporary group structure.