CALVING RATE OF COWS UNDER CAATINGA CONDI TIONS AS AFFECTED BY DRY-SEASON SUPPLEMENTARY GRAZING ON BUFFEL-GRASS

The study was designed to evaluate the effects of buffelgrass (Cenchru s ciliaris, L.) dry-season grazing on seasonal liveweight changes and on annual calving rates of native x Zebu cows, raised extensively on c aatinga vegetation. Forty-two mature cows were assigned to two 21-cow treatments: (C) continuous yearlong grazing on caatinga (08 ha/cow), a nd (CB) continuous rainy-season grazing on caatinga and continuous dry -season grazing on buffel-grass paddock (01 ha/cow). The study was car ried out over a three-year period. At the end of the experimental peri od, CB cows were 85.4 kg heavier (P < 0.05) than the C ones. Annual ca lving rate showed by CB cows was significantly higher (P < 0.05) than the rate observed for the C cows. In terms of number of calves born, t he increase showed by CB group reached 56% indicating the depressive e ffect on fertility of C cows, caused by heavy liveweight losses, as a result of prolonged periods of undernutrition.