151
Growth, Performance, and Carcass Characteristics of Feedlot Holstein Steers Fed Ractopamine Hydrochloride

Monday, March 12, 2018: 3:45 PM
214 (CenturyLink Convention Center)
Catherine L Haviland, Oklahoma State University, Stillwater, OK
Chris J Richards, Oklahoma State University, Stillwater, OK
Jake A Reed, Oklahoma State University, Stillwater, OK
Maggie E Youngers, Oklahoma State University, Stillwater, OK
Steven T Quanz, Oklahoma State University, Stillwater, OK
Caleb G Lockard, Oklahoma State University, Stillwater, OK
Mariah A. Woolsoncroft, Oklahoma State University, Stillwater, OK
Taylor C Husz, Oklahoma State University, Stillwater, OK
Carla L Goad, Oklahoma State University, Stillwater, OK
Todd A Jackson, Department of Veterinary Clinical Science, Oklahoma State University, Stillwater, OK
D. L. Step, Department of Veterinary Clinical Science, Oklahoma State University, Stillwater, OK
Marilyn Corbin, Zoetis, Florham Park, NJ
Clinton R. Krehbiel, Oklahoma State University, Stillwater, OK
Audio File Recorded Presentation (mp4)
Growth-promoting technologies improve feedlot performance and carcass characteristics of cattle. The objective was to determine the effects of dose and duration of ractopamine hydrochloride (RH; Actogain, Zoetis) on feedlot performance and carcass characteristics when fed to Holstein steers. A randomized complete block design was used with a 3 × 3 factorial arrangement of treatments with three RH doses (0, 300, or 400 mg∙steer-1∙d-1) fed for three durations (28, 35 or 42 d). Holstein steers (n = 855; initial BW = 448 + 37 kg) were blocked by BW (15 blocks) and randomly allocated to 1 of 9 treatment pens approximately 72 d before harvest. Pen weights, chute temperament and animal mobility were determined during the RH feeding period. At harvest, carcass data were collected on all steers, and tenderness was measured on steaks from 3 or 4 randomly selected steers from each pen. Slice shear force (SSF) was determined after steaks were aged for 14 or 21 d. Increasing RH dose linearly increased ADG and G:F (P = 0.002), while BW gain increased linearly with RH dose and duration (P < 0.003). Hot carcass weight (P = 0.02) and LM area (P = 0.001) increased linearly with increasing RH dose. The percentage of carcasses in the USDA Yield Grade 2 category increased (Linear effect, P = 0.008) and percentage USDA Yield Grade 4 carcasses tended (P = 0.08) to decrease when RH increased. After aging steaks for 14 or 21 d, SSF increased linearly (P < 0.002) with increasing RH dose. In the 14-d aged, the percentage of steaks with SSF < 15.3 kg decreased linearly (P < 0.001) while the percentage of steaks with > 20.0 kg SSF increased linearly (P < 0.001) with increasing RH dose. After 21-d aging, there was a tendency (P = 0.06) for a higher percentage of steaks from steers fed RH to have SSF > 20.0 kg, but no difference (P > 0.12) in the percentage of steaks with SSF < 19.9 kg. Final chute temperament (P > 0.45) and animal mobility (P > 0.67) were not affected by feeding RH. Increasing dose of RH fed for 28 to 42 d before harvest increased BW gain, gain efficiency, HCW, and LM area when fed to Holstein steers with no negative effects on behavior or mobility. Percentage of steaks classified as not tender improved when steaks were aged for 21 d.
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