Effects of Stocking Density on Steer Performance and Carcass Characteristics in Bedded Hoop Barns

摘要

Use of bedded hoop barns for feeding cattle has grown in part due to increased regulations regarding open feedlot runoff. In 2010, ISU estimated almost 700 hoop barns in Iowa used for beef cattle and more than 80% were used for cattle feeding. Work in Iowa also has documented that cattle confined in a bedded hoop barn perform similarly to cattle fed in an open feedlot with shelter. The work was done with a stocking density of 50 sq ft per steer in the bedded hoop barn. A hoop barn is a more expensive facility system compared with open lot configurations. Fixed costs per steer (facilities) are partially determined by stocking density. The objective of this study was to determine the effects of increased stocking density on performance and carcass characteristics of steers fed in bedded hoop and bedded open front facilities.The trials were conducted in 2008 to 2011 at the ISU Armstrong Research Farm, Lewis, IA. The hoop barn was stocked with 40, 45 and 50 head per pen resulting in 50, 45 and 40 sq ft per steer, respectively. There was one stocking density per housing type per trial. The diet fed was 45.0% dry corn, 14.8% ground hay, 36.8% modified distillers grains and 3.4% supplement on an as-fed basis. The total diet was approximately 69% dry matter.Cattle growth rate (ADG), feed intake (DMI), feed efficiency (F/G) and mean mud score did not differ based on stocking density (P\u3e0.05). However, the cattle given more square feet numerically had greater feed intake and were more efficient (about 4-5%) than the more densely stocked cattle. This study may not have had enough replications to detect statistically significant differences. Also the mean carcass characteristics (fat cover, rib eye area, marbling score, quality grade and yield grade) did not differ by stocking density (P\u3e0.05).When comparing seasons only, steers fed in summer tended to have heavier market liveweight, heavier carcass weight, required less feed per liveweight and less marbling compared with steers fed in winter (P≤0.10). Also, the summer-fed steers grew faster and gained more liveweight than the winter-fed steers (P\u3c0.005).These results suggest that this study may not have reached the maximum stocking density for feeding beef cattle in a bedded hoop barn. In other words, market cattle can probably be stocked at less square footage per steer than the 40 sq ft per steer used in this study. Observations of farmers with hoop barns suggest that 37 or 35 sq ft per steer may be feasible.Several factors may affect stocking density including genetics or frame size of the cattle and may interact with season. Also, it should be noted that as the density of cattle increases, more management is required, i.e., more bedding, more bunk space, more waterer space and observing individual cattle for health issues becomes more difficult.