Effects of Feeding a Moderate-Energy Diet before a High-Energy Finishing Phase in Steers Implanted with Revalor-XS on Performance and Carcass Characteristics

It was hypothesized that sequential delivery of Revalor-IS and Revalor-S, as occurs with Revalor-XS implant, will complement effects of feeding a moderate-energy diet for a short time before finishing. One-hundred ninety crossbred steers (352 kg) were utilized in a generalized randomized block design experiment to determine the effect of a short-term, moderate-energy feeding phase in steers implanted with Revalor-XS on performance and carcass traits. Treatments consisted of feeding a moderate-energy diet for 63 d (within Revalor-IS delivery window) before transitioning to a high-energy diet (MdE; 1.28 Mcal/kg DM) during finishing or feeding a high-energy throughout the feeding period (HiE; 1.41 Mcal/kg DM). Steers were initially blocked by weight and randomly allocated to pens. Pens were randomly allocated to treatments. This resulted in heavier initial BW for MdE steers (356 vs 349 kg). Subsequently, initial BW was used as a covariate instead of weight block. Steers were marketed when they were considered to have > 1.27 cm fat cover as appraised visually. Days on feed during finishing (113 d) or total days on feed (176 d) did not differ (P > 0.10). As expected, daily DMI and total DMI during the first 63 d were greater (P < 0.0001) for steers fed MdE. A trend for greater DMI (P < 0.10) was observed during finishing for steers fed MdE. These differences led to steers fed MdE to have greater daily DMI (P < 0.01) during the entire feeding period. However, these differences were not reflected by total DMI during finishing or the entire feeding period. Total concentrate (defined as 100 – corn silage concentration) intake by cattle fed MdE was lower (P < 0.0001). Rate of gain and feed conversion derived from live final BW or carcass-adjusted final BW were not affected (P > 0.10) by treatment. Because rate of gain was not affected by MdE, BW or final BW (live or carcass-adjusted) was not different (P > 0.10). Carcasses of steers fed MdE had lower marbling scores (P < 0.05). This led to a trend (P < 0.10) for greater incidence of Select and lower incidence of premium Choice carcasses. Feeding a moderate-energy diet during a short time before transitioning to finishing in steers implanted with Revalor-XS led to similar feedlot performance albeit with lower reliance on concentrate feed ingredients. However, this advantage may be offset by reductions in carcass quality.