Conformation, precocity and musculature visual scores adjustment factors for age of dam at calving, Julian date of birth and age of calf at weaning, in nelore cattle breed

For this study, after editing the data, 87,372 Nelore cattle visual scores of conformation (C), precocity (P) and musculature (M) at weaning were utilized. The aim of this work were to study the effects of age of dam at calving, Julian date of birth and age of calf at weaning on conformation, precocity and musculature visual scores and to estimate adjustment factors for these effects. The model included fixed effects of contemporary group (herd, paddock, year and month of birth, sex and management group at birth and at weaning), and the effects of age of dam at calving (for each sex), Julian date of birth and age of calf at weaning as covariables. A quadratic -quadratic segmented polynomial was utilized for age of dam at calving. For Julian date of birth a segmented polynomial with three quadratic segments was considered, whereas a quadratic ordinary polynomial was used for age of calf at weaning. Every effect included in the model significantly influenced the visual scores. Only including the month or season of birth in the contemporary group definition was not sufficient to adjust for differences in visual scores due to date of birth. For genetic evaluations of animals the visual scores at weaning must be adjusted for age of dam at calving, Julian date of birth and age of calf at weaning.