Carcass gain, efficiency, quality, and profitability in steers at extended days on feed

Abstract Text: Crossbred steers (n = 114, initial BW = 334; SD = 30 kg) were utilized to evaluate the change in carcass composition throughout the feeding period and the economic profit/loss realized by feeding cattle 0, 22 and 44 days longer than the industry average. Steers were assigned randomly to 1 of 3 pens and stepped up on a common finishing ration 24 d prior to the start of the study. On d 1, cattle were weighed and assigned randomly to 3 serial harvest groups within pen, allowing for 38 steers per harvest (1/3 of each pen). Steers were fed a common finishing ration using the GrowSafe system, allowing for calculation of daily individual feed intake and individual steer to serve as the experimental unit. Carcass ultrasound measurements of LM area, intra-muscular fat percentage, and 12^th rib fat thickness were collected on 76 steers (2 pens) at 1, 78, and 134 days on feed (DOF). Steers were considered industry average when the group assigned to the first slaughter averaged 1.3 cm for 12^th rib fat thickness (142 DOF). The second and third slaughter groups were harvested at 163 and 185 DOF, respectively. Economic assumptions were applied to steers to determine profit/loss per steer when feeding longer DOF. Steer DMI was not different among DOF while live ADG and live G:F decreased linearly (P ≤ 0.04) as steers were fed to longer DOF. However, HCW increased linearly (P < 0.01) from 374 to 410 kg, as steers were fed from 142 to 185 DOF. Steer LM area quadratically increased (P = 0.04) from 89.0 to 93.5 cm² (142 and 163 DOF, respectively) and remained constant for 185 DOF at 92.3 cm². Marbling score numerically increased from 475 to 506 (142 and 185 DOF, respectively) but was not significantly different. Calculated YG and 12^th rib fat thickness increased linearly (P < 0.01) as DOF increased for steers. Total feedlot costs linearly increased (P < 0.01) from $431.33 to $551.14 (142 vs 185 DOF, respectively) while profit per steer tended to increase linearly (P = 0.14) from 142 to 185 DOF ($18.78 vs $79.30, respectively). The increase in profit despite the added total feedlot costs can be attributed to more HCW sold and a potential increase in QG premiums. When comparing economics at current market conditions, steers can be fed for 44 days longer and increase profit even though HCW and YG discounts increase.

Keywords: carcass traits, feeding duration, profit