The effects of age of dam (IDV) and julian birth date (DJN) on daily weight gain of beef calves from birth to wean were analyzed and correction factors were calculated. Data from 463,971 and 39,220 Nelore and Tabapuã animals were used in the analyses. The IDV, modeled by a polynomial segmented quadratic-quadratic with a knot at seven years and DJN modeled by a polynomial segmented with three quadratic segments and two knots at 185 and 295 days were included in the statistical model. The IDV and DJN had significant effects on daily weight gain of beef calves from birth to wean, and significant difference between breeds was observed for both effects. The best daily weight gain from birth to wean was observed for cows averaging 6 and 9 years for Tabapuã and Nelore breeds, respectively. The best daily weight gain from birth to wean was also observed in the winter for both breeds. Correction factors were calculated for breed, and those for IDV were calculated separately for males and females. The correction factors for DJN were calculated for each season. The calculated correction factors allowed higher precision in the selection of animals by reducing the non genetic effects on the variation of daily weight gain from birth to wean.
beef cattle; Zebu; adjustment factor; segmented polynomial; wean
