Crecimiento de terneros lactantes y producción lechera de un rebaño de vacas Retinto en la Dehesa

Calves growth and milk production of Retinto beef cows were studied in Southwest of Spain. Data were taken in 1979-80 and 1980-81 at «El Gaitán» ranch located at the San Pedro mountain (Cáceres). Calves were weighed at birth and later from 20 days of age until weaning (~ 7 months) each 35 days, also was estimated milk production by the calf nursing method. Environmental factors considered in the study were: calving season, sex, year, and two-way interactions among these factors, and the linear and quadratic effeets of age of cow, gestation number and age of calf. In the study of calves growth were also considered the linear and quadratic effeets of milk production. Using the stepwise regression technique, the variables which have more influence on calf growth and milk production accumulated at wean- ing have been selected. The nine variables selected for calf growth explain- ed 94.6 % of the variability, being calf age and milk production the most important (R2 = 91.9%); when calf age is excluded from the model, milk production itself explains 77.6 % of the variation on calf growth. Consi- dering milk production as a dependent variable, a group of seven varia- bles explained 72.6 % of the variability of this characteristic, being the suckling days the variable that affects more to this response (R2 = 66.7 %). 174