Avaliação da ocorrência de perdas gestacionais em novilhas Nelore superprecoces : um estudo de levantamento de dados

Abstract

The intensification of cattle production has driven the adoption of reproductive biotechnologies and selection strategies aimed at sexual precocity to reduce age at first calving and improve herd productivity. In this context, super-early heifers represent an important tool for accelerating genetic gain and enhancing reproductive performance. However, pregnancy loss after pregnancy diagnosis remains a major challenge to the reproductive efficiency of these young females. Thus, the objective was to evaluate the frequency of gestational loss after pregnancy confirmation and to verify the association between age, body weight, and body condition score (BCS) with pregnancy outcome in superprecocious Nellore heifers, with an average age of approximately 14 months. A retrospective observational study was conducted using 314 reproductive records. For the analysis of factors associated with pregnancy maintenance, 152 heifers with a positive pregnancy diagnosis were included and allocated into two groups: calved (n = 84) and did not calve (n = 68). Frequencies, means, standard deviations, confidence intervals, and effect sizes were calculated. Means were compared using the independent samples t-test, adopting a significance level of 5%. Among the heifers with confirmed pregnancy, 55.3% calved, whereas 44.7% had no calving record. No significant differences were observed between the groups regarding age (13.99 ± 0.89 vs. 13.92 ± 0.97 months; p = 0.654), body weight (365.00 ± 28.87 vs. 367.92 ± 31.57 kg; p = 0.557), or BCS (3.57 ± 0.13 vs. 3.58 ± 0.13; p = 0.525). Effect sizes were small, indicating low magnitude of the observed differences. Under the conditions of this study, age, body weight, and BCS, when evaluated individually, were not associated with pregnancy loss. The high proportion of heifers without a recorded calving after a positive pregnancy diagnosis highlights the need to verify the consistency of reproductive records and to investigate other factors potentially involved in pregnancy maintenance, including sanitary, nutritional, genetic, environmental, and management-related factors.