ESTÁGIO OBRIGATÓRIO EM SAÚDE PÚBLICA E DEFESA SANITÁRIA E TRABALHO DE CONCLUSÃO DE CURSO: ASSOCIAÇÃO ENTRE CARACTERÍSTICAS DE CARCAÇA E EFICIÊNCIA REPRODUTIVA EM NOVILHAS NELORE.

Abstract

Reproductive efficiency is one of the main determinants of productivity in beef cattle. It is modulated by genetic and nutritional factors that influence the body composition of females and, consequently, reproduction. This study analyzed the relationship between carcass variables and pregnancy rate in Nelore heifers, using ultrasonography as the method for measuring body composition. Data from 659 Nelore females were used, aged between 18 and 36 months, including body weight (kg), ribeye area (REA, cm²), subcutaneous fat thickness (SFT, mm), and rump fat thickness (RFT, mm). Logistic regression models indicated a significant effect of body weight and SFT (p < 0.05) on the probability of pregnancy. There was a negative trend for body weight and a positive trend for SFT. This indicates that lighter animals with greater subcutaneous fat deposition, meeting an early-maturing biotype, have a higher probability of becoming pregnant when compared to animals of the same age. In contrast, REA and RFT did not show a significant effect, suggesting that muscle development, evaluated by REA, and fat deposition in the rump region have a secondary influence on the fertility of females within the age range evaluated in this study. Despite the limitations resulting from the lack of standardization of age and, consequently, physiological condition of the animals in the dataset used, the results demonstrated a relationship between body weight and fat deposition in the carcass with the pregnancy rate. Females, within the age range evaluated, with lower body weight and greater subcutaneous fat deposition tend to present higher pregnancy rates.