The objective of this study was to evaluate milk production of primiparous beef cows and growth of calves of two genotypes from birth to weaning. Forty eight Hereford heifers with average age of 3 years grazing only native pastures were used. Sixteen cows were inseminated with Red Angus (Bos taurus) semen and 32 with Nelore (Bos indicus). Effects were calf genotype (GENOT) - Bos taurus x Bos taurus and Bos taurus x Bos indicus, calving season (EPOCN), concentrated in Spring and distributed over three periods: 1S (September), 2O (October) and 3N (November and December), and calf sex (SEXO). Ten measurements of milk production obtained by the indirect method, weighing the calf before and after suckling, were performed at 21 day intervals. Overall average milk production for the entire experimental period was 4.80 ± 0.09 kg/day. No significant differences were observed on milk production for all variables studied. Calf weight gain was significantly affected by EPOCN but not by GENOT or SEXO. It was concluded that milk production of beef cows, under extensive field conditions, was not affected by the GENOT, EPOCN and SEX. Calf growth depended on EPOCN.
calf weight gain; lactation; beef heifers