SEXUALLY DIMORPHIC ENVIRONMENTAL SENSITIVITY IN BEEF CATTLE STUDIED BY PRINCIPAL COMPONENT ANALYSES IN A DEVELOPMENTAL REACTION NORM MODEL

Abstract Text: Selection in heterogeneous environments has had increasing importance since production system definition is linked to economic instability and climatic changes. The aim of this work was to compare environmental sensitivity between sexes and along development. Data were collected in 366 Brazilian herds for the Brazilian Nelore Cattle Breeding Program with 1,110,662 body weights from 408,416 animals. Eight different analyses were applied using a principal component analysis of the cubic polynomial random regression coefficients’ estimates, with a sex-separated developmental reaction norm approach. Results showed different estimated eigenvalues for coefficients of different orders in different sexes. Eigenvalues of level and slope coefficients explained a great majority of the variation of Nelore beef cattle weight in Brazilian production systems, with a distinguished increase of slope coefficient eigenvalue in female analyses along the age axis when compared to male analyses.

Keywords:

environmental sensitivity

principal component analysis

reaction norms

sexual dimorphism