Efeito da ingestão de cromo sobre o ganho de peso e de alguns constituintes sangüineos de bovinos mantidos em pastagens no cerrado

Abstract

With the objective of to evaluate the performance of steers belonging to the groups racial Bos indicus (Nelore) and crossbreed Bos taurus (crossbreed holstein) in intensive grazing, during the dry (DS) and rainy stations (RS), with offer or not of organic chrome (OC) and of artificial shadow, 20 bovine of each racial group were distributed equally among the treatments T1(mineral supplement with inorganic source of chromium, without shadow), T2 (T1 more shadow), T3 (mineral supplement with organic source of chromium, without shadow) and T4 (T3 more shadow), with randomized entirely design experimental in factorial scheme 2x2x2. The weightings and crop of blood of animal happened every 28 days. The appraised sanguine parameters were the leukocytes and the cortisol, glucose, protein, urea, calcium and phosphorus values. Daily the climatic data and the consumption of the mineral supplements were logged. During the DS and RS, Nelores presented larger concentrations of cortisol (7,46 and 4,81 µg/dL), glucose (79,83 and 90,17 mg/dL), urea (27,40 and 32,5 mg/dL) and phosphorus (6,04 and 6,68 mg/dL); in this same period, the bovine suplemented with OC presented larger protein level (7,60 and 7,56 mg/dL) (P< 0,05). The consumption was larger (P< 0,05) for the supplement with OC (159,7 g/UA/day). OC and also the shadow made possible larger earnings in weight (0,189 and 0,194 kg/day, respectively) for the race Nelore in the DS (P< 0,05); in RS, the inorganic chrome (IC) it propitiated larger performance (P< 0,05) to the crossbreed holstein (0,871 kg/day). The association of the OC with shadow guaranteed better results to Nelores (0,250 kg/day) and to the crossbreed holstein (0,240 kg/day) during the RS (P< 0,05). Conclude that the treatment T4 came more efficient, mainly in the DS.