Supplementation of growing bulls grazing Panicum maximum cv. Coloniao increases average daily gain and does not impact subsequent performance in feedlot phase

ABSTRACT To evaluate the influence of supplementation strategies on the average daily gain (ADG) of cattle in a rotational grazing system of Guinea grass (Panicum maximum cv. Coloniao) pastures during the rainy season. It was further evaluated the residual effects in the feedlot finishing phase. Seventy-five 8 month-old crossbred bull calves averaging 200.1 ± 2.5 kg of body weight (BW) were stratified and grouped in three into 25 blocks according to BW, and then randomly assigned to one of three supplementation treatments: control (no supplement), energy supplement [65 g crude protein (CP)/kg dry matter (DM)] or protein supplement (200 g CP/kg DM) both fed as 6 g/kg BW. All animals composed a single herd and were separated daily according to treatment groups for supplementation. After the grazing phase, all animals were moved to a feedlot and received the same diet up until slaughter. Guinea grass was subjected to rotational stocking with pre- and post-grazing heights of 76 and 43 cm, respectively. Energy and protein supplements provided similar ADG (P > 0.05; 0.94 kg/day) which was greater than for non-supplemented animals during the grazing phase (P ≤ 0.05; 0.74 kg/day), but there was no difference in the subsequent feedlot phase (P > 0.05; 1.45 kg/day). The protein supplement had no incremental effects over the energy supplement on ADG and carcass traits of growing crossbreed bulls during the grazing phase, indicating that either source could be used, and that an energy supplement would lead to more efficient nutrient use coming from the grass.