Análises multivariadas para medidas de carcaça em tempo real e peso em bovinos Nelore ao sobreano

Abstract

Carcass traits predicted by ultrasonography have been considered in genetic evaluation programs for beef cattle, seeking high quality carcasses, through investment in genetic improvement, nutrition and animal welfare. The present work aimed to evaluate the weight ratios in different ultrasound measurements during the yearling in a beef cattle system in Nellore cattle and the influence of sex on ultrasound measurements. The study was carried out using pedigree and performance information from the Projeto Nelore Birigui herd, using information from calves from the years 2020 and 2021. at 205 days of life. The measurements were: loin eye area, loin eye area for 100 kg of live weight, subcutaneous fat thickness, subcutaneous fat thickness for 100 kg of live weight, rump fat thickness, degree of marbling, width ratio and sirloin height and yearling weight. This information was subjected to cluster and principal component analysis according to the sex of the animals. Male Nellore animals belonging to group 3 were superior for most characteristics compared to the others, except for loin eye area per 100 kg of live weight. However, the females did not present a superior group than the others, since the characteristics of carcass and weight at 450 days were heterogeneous and well distributed among all. With regard to the sex effect, all the characteristics evaluated in the animals were different between male and female animals, except ribeye area for 100 kg of live weight. The characteristics that showed the most moderate and high correlations were subcutaneous fat thickness and loin eye area, thus being able to select them and, consequently, the others will be improved in male and female animals of the Nellore breed. Regarding the principal component analysis, the characteristics most correlated with the first principal component were marbling, subcutaneous fat thickness and subcutaneous fat thickness for 100 kg of live weight. The principal components analysis of the sex effect showed that the first three principal components were responsible for at least 70% of the total variance and the most important characteristics for the first principal component between males and females were the same. However, the characteristics of subcutaneous fat thickness, rump fat thickness and marbling were more correlated with each other and with the others, indicating that the selection for these characteristics will also select superior animals for the others.