Modelos hierárquicos bayesianos na estimativa de interação genótipo x ambiente para resistência ao carrapato em bovinos de corte Hereford e Braford via normas de reação

The existence of genetic x environment interaction (GxE) was evaluated based on models with different genetic and residual variance presumptions for tick resistance in Hereford and Braford beef cattle. Seven models were studied: a standard animal model (AM) and six as hierarchical reaction norm models (HRNM). The deviance information criterion (DIC) revealed that the 1-step HRNM with heterogeneous residual variance based on eight subclasses of contemporary group infestation level yielded the best fit to the data. The AM heritability was lower when compared to HRNM in environmental with medium and high tick infestation levels and superior in low infestation level. The GxE was observed by crosses among animals linear reaction norms along the environmental gradient. The HRNM are useful tools to identify GxE in tick resistance of Hereford and Braford beef cattle.