Comparative study between birth month and weaning weight of purebred Nelore cattle from embryo transfer and artificial insemination in the municipality of Vilhena – RO, Brazil

Productive and reproductive characteristics positively or negatively determine the efficiency of livestock farming. Therefore, it is important to take into account environmental effects that directly affect characteristics of economic interest in animal farming. A classic example is the calf birth period, which has a strong relationship with weaning weight. In view of this, the present project aimed to evaluate the influence of the month of birth on the weaning weight of animals of the Pure Origin (PO) Nelore breed from two farms in the municipality of Jaru, Rondônia. The data were evaluated to find the average of the batch of animals evaluated, spreadsheets containing information on the day of birth and weight of the animals at weaning. The spreadsheets are part of the database of the evaluation programs, National Association of Breeders and Researchers (ANCP) and Zebu Genetic Improvement Program (PMGZ), which were correlated to find factors that influence the performance of the animals. Data from 1,253 animals of the Nelore breed were used. The weight at 210 days of age was evaluated taking into account the months of birth of the animals. The individuals that obtained the best performance at weaning were those born in the months of July, August and September, corresponding to the months of the breeding season of the previous year. From the evaluation it was possible to determine the best month for reproduction of the matrices, and consequently the birth of the calves aiming at better performance of the progenies.