Análise de dados com medidas ultrassonográficas repetidas em bovinos de corte

Abstract

Brazil is a country that has high animal productivity, and beef cattle is one of the segments of production that most demand technologies, which are now applied to improve the quality of beef produced and meet the most demanding consumers. Therefore, the experiment aimed to analyze data from repeated ultrasound measurements in beef cattle. Data from entire Nellore males from a commercial herd were used. From each individual, at weaning (210 days) to yearling (550 days) and pre-slaughter (660 days), repeated measurements of weight and ultrasound (loin eye area - AOL, marbling - MAR and of subcutaneous fat – EGS). Models were adjusted having as explanatory variables year of birth, ultrasound measurements and classes for the response variables (weight, AOL, MAR and EGS), which were dichotomized. The SAS software MIXED procedure was used to adjust the models. With the inclusion of the dichotomized variable in the model, an interaction of the classes with the measures was observed, with a significant effect of the classes ("high" and "low"), indicating that throughout the evaluated period there is no change in the classification of the averages of the formed groups. Thus, the formation of dichotomous classes and the maintenance of the classification of groups throughout the measurements indicate that ultrasound measurements at weaning can be an alternative for early selection of animals.