Repeated measures in the study of growth and ultrasound carcass traits in cross heifers

Yokoo, Marcos Jun-ItiOrtelan, Alex ArceliSarmento, José Lindenberg RochaRosa, Guilherme Jordão de MagalhãesCardoso, Fernando FloresAlbuquerque, Lucia Galvão de

The aim of this paper was to study the development of carcass traits obtained by ultrasound, weight, chest circumference and hip height by longitudinal data of two genetic groups of heifers. These data were analyzed by different structures of residual (co)variance consider homogeneity or heterogeneity of (co)variances to better represent the variability between and within individual observations over the time. The traits were obtained in 60 animals ½ Braunvieh x ¼ Santa Gertrudes x ¼ Nelore and 60 animals ½ Santa Gertrudes x ½ Nelore. The traits were evaluated at intervals of 28 days. The comparison was done with several models, based on the criterion SBC (Schwarz’s Bayesian Criterion) with the goal of identifying structures of residual (co) variance more appropriate to best represent the variation of the measures within individuals. Later, as the animals were measured at different ages, it was evaluated the most appropriate model to regress these traits as a function of age, using ordinary polynomials and verifying the need for different curves for each genetic group. The results indicated that it should consider different structures of residual (co)variance to better represent the variability between and within individual observations. For weight, hip height, chest circumference and longissimus muscle area traits there are differences in the genetic group over the time.(AU)

1. hip height
2. longissimus muscle area
3. circunferência torácica
4. polinômios ordinários
5. chest circumference
6. área de olho de lombo
7. ordinary
8. altura do posterior
9. estrutura de(co)variância
10. covariance structure