10 Finishing beef cattle under cover reduces heat load and improves efficiency during the summer

Heat-stress in finishing cattle presents a significant risk to efficiency and economic viability. The project objective was to quantify the effects of long-term heat stress when finishing cattle during the summer in the southeastern United States. Forty-five Angus crossbred steers (446±23 kg) were blocked by weight and randomly assigned to environmental finishing treatments including: covered with fan (CWF), covered without fan (CNF), or outside without shade (OUT). For 92 d steers were individually fed a typical feedlot ration. Environmental data were continuously recorded including: black globe temperature (BG), heat load index (HLI), and accumulated heat load units (AHLU). Feed intake was recorded daily, and steers were weighed every 20–25 days. When the first treatment averaged 613-kg all steers were slaughtered, and carcass data were collected. Data were analyzed as a Mixed Model (JMP V13; SAS Inst.) and means were separated (Least Squares Means). Average maximal BG was lower for covered finishing than OUT (P < 0.01) however for HLI CWFCNF>OUT, while G:F was similar (P = 0.22) between CWF and CNF, which were greater (P < 0.01) than OUT. Hot carcass weights were heavier for CWF than OUT (P < 0.01) and CNF was similar to both (P ≥ 0.11). There was no difference for USDA Yield Grade (2.6; P = 0.44), or marbling score (Modest20; P = 0.76). Steers finished under cover were more efficient than steers finished in open dry-lots. The addition of cooling fans further improved steer gains over those that were covered without fans.