It was used 17,767 weight records of 4,210 Santa Inês breed lambs aiming to compare random regression models with different structures to model the residual variance in genetic studies of the growth curve. The fixed effects included in the analysis were contemporary group and age of the ewe at lambing. Fixed and random regressions were fitted through Legendry polynomials of orders 4 and 3, respectively. The residual variance was fitted by heterogeneous classes and by functions of variances employing ordinary […]

Records of 7,271 weights of 952 lambs measured from birth up to 196 days of age between 1983 and 2000, available from the Agricultural Research Corporation of Paraiba database, were used to model the average growth curve of Santa Ines sheep. The influence of environmental effects on the estimated parameters of the Brody, Von Bertalanffy, Logistic, Gompertz and Richards functions was evaluated using the NLIN procedure of SAS. The growth curve was well fitted by all models but larger residual […]

Records from an unselected flock of Morada Nova sheep collected over an 11-year period (1981 to 1991) were used to evaluate environmental sources of variation affecting growth traits. The effects of year of birth to yearling (A), sex of lamb (S), type of birth (T), and weigth of ewe at lambing (P) were important sources of variation to explain differences in weigth at birth (PN), weaning (PD), six- months (PM6) and 12 months (PM12) of age. Males were heavier than […]

The objective of this work was to estimate the (co) variance components and direct and maternal heritability of the body weights of sheep of Santa Inês breed. A total of 3,771 lambs weights records of the Santa Inês hair sheep breed, progenies of 114 sires, and 758 ewes were analyzed, obtained from experimental herds of EMBRAPA – SNPA from 1985 to 1995. The covariance components and genetic parameters from additive genetic effects, maternal and permanent environmental effects, as well as […]