Performance of beef cows of different genetic groups in natural and cultivated pastures

Resumo

The objective was to assess the performance of 96 pregnant cows of the genetic groups (GG) Charolais (C), Nellore (N), ½ CN and ½ NC, subjected to the following treatments: kept exclusively in natural pastures (NP) throughout the experimental period; kept in cultivated pastures (CP) from July 15 to Setp 15 (CPNP) or from Sept 15 to Nov 15 (NPCP) and the remainder of the experimental period in NP. The weight at the end of the first grazing period (Sept 15) was higher for the CPNP cows than those of the NPCP and NP. The weight at the end of the second period (Nov 15) was 456, 428 and 392 kg respectively for NPCP, CPNP and NP. At calving, the heaviest cows were the CPNP, followed by the NPCP and the NP. At weaning, 90 days postpartum, the heaviest were the NPCP, followed by the CPNP and NP. Nelore cows were less heavy in all evaluations, followed by C, with the F1s' weight higher than the purebreds. The grazing sequences did not affect the percentages of the cows in estrus and pregnancy, but did influence the invervals between calving and first estrus postpartum (ICE). The GG influenced the rate of cows in estrus, pregnant and the ICE which was lower in the F1 (103 days), followed by the C (109 days) and had the largest interval N (119 days). The grazing sequences affect the average daily weight gain (ADG) of calves until weaning at 90 days of age. The GG of the calf affected the ADG at to 210 days.