Avaliação de modelo preditivo da produção de leite de vacas de corte e impactos na eficiência produtiva e reprodutiva durante a lactação

Abstract

Milk production in beef cows is crucial for the development of calves, directly influencing their weight at weaning. Lactation is a physiologically dominant state where changes and adaptations in the metabolism, organs and tissues of cows occur to promote milk synthesis. The objective is to evaluate characteristics related to the lactation of beef cows at strategic moments and potential impacts on productive and reproductive performance. The Aberdeen Angus, Hereford, Charolais and Nelore breeds were studied, with data collected over 11 years. 233 lactating cows, kept on natural pasture, were used to evaluate live weight, pregnancy diagnosis, calf weight and milk production on different days during lactation (21 to 189). Statistical analyses, carried out with SAS®Studio software, included Pearson correlation and multiple regression methods to estimate average daily milk production. The results demonstrated three important collection dates for estimating milk production for the Hereford, Charolais and Nelore breeds, these being days 168, 126 and 63; 168, 105 and 42; 42, 84 and 189 respectively. For milk production and net energy for calf weight gain, they are similar to pregnant and empty cows, that is, milk production does not interfere with reproductive efficiency. Another important result is that the liquid energy of milk is sufficient for calves until the fifth month, but after that, it is necessary to add other foods to continue weight gain.