PSXIII-3 - Effect of Pen Stocking Density on Animal Performance, Social Behavior, and Animal and Pen Dirtiness in Holstein Bulls Fed High-concentrate Diets

Abstract: The aim of this study was to evaluate the effect of pen stocking density on animal performance, social behavior, and animal and pen dirtiness in fattening bulls. Two hundred sixty-three bulls (250 ± 24.7 kg BW, and 193 ± 13.2 d age) were group-housed and fed concentrate and unprocessed straw separately, both ad libitum. Animals were assigned to one of 2 different pen stocking density treatments: 1) LOW (n=112), 14 bulls/pen (5.1 m²/bull and 5 bulls/feeding space); and 2) HIGH (n=151), 19 bulls/pen (3.6 m²/bull and 7 bulls/feeding space). The study lasted 183 d. Pen concentrate intake was recorded daily. Bulls were weighed every 2 wk. Social behaviors (from d 59) and animal and pen dirtiness (from d 120) were recorded every 4 wk. Carcass quality was recorded at the slaughterhouse. Data were analyzed with a mixed effects model. Concentrate intake was not affected by treatment, but ADG (1.57 vs. 1.47 ± 0.027 kg/d) and feed efficiency (0.21 vs. 0.20 ± 0.007 kg/kg) were greater (P≤0.05) in LOW than in HIGH. Carcass quality was similar between treatments, but preslaughter weight (552 vs. 535 ± 4.6 kg) and hot carcass weight (292 vs. 284 ± 2.9 kg) was greater (P<0.01) in LOW than in HIGH. Eating and ruminating were greater (P<0.05) in LOW than in HIGH, and lying was greater (P=0.01, treatment by time interaction) in LOW than in HIGH at d 89 and d 120. Animal dirty score was lesser (P≤0.01) in LOW than in HIGH (0.0 vs. 7.5 ± 1.33 %), and pen dirty scores were lesser (P≤0.01) in LOW than in HIGH in d 120. In conclusion, decreasing pen stocking density by 42 % improves animal growth and efficiency, behaviors indicative of greater welfare and comfort, and cleanliness in fattening bulls.