Growth, performance, and carcass characteristics of feedlot Holstein steers fed ractopamine hydrochloride.

Autor:	Lockard CL; Department of Animal and Food Science, Oklahoma State University, Stillwater, OK., Richards CJ; Department of Animal and Food Science, Oklahoma State University, Stillwater, OK., Lockard CG; Department of Animal and Food Science, Oklahoma State University, Stillwater, OK., Youngers M; Department of Animal and Food Science, Oklahoma State University, Stillwater, OK., Woolsoncroft MA; Department of Animal and Food Science, Oklahoma State University, Stillwater, OK., Husz TC; Department of Animal and Food Science, Oklahoma State University, Stillwater, OK., Wilson BK; Department of Animal and Food Science, Oklahoma State University, Stillwater, OK., Goad CL; Department of Statistics, Oklahoma State University, Stillwater, OK., Jackson TA; Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK., Step DL; Department of Veterinary Clinical Science, Oklahoma State University, Stillwater, OK., Bernhard BC; Zoetis, Parsippany, NJ., Corbin MJ; Zoetis, Parsippany, NJ., Krehbiel CR; Department of Animal and Food Science, Oklahoma State University, Stillwater, OK.
Jazyk:	angličtina
Zdroj:	Translational animal science [Transl Anim Sci] 2019 Oct 04; Vol. 4 (1), pp. 102-117. Date of Electronic Publication: 2019 Oct 04 (Print Publication: 2020).
DOI:	10.1093/tas/txz157
Abstrakt:	Growth-promoting technologies such as implants, ionophores, and β-agonists improve feedlot performance, efficiency, and carcass characteristics of cattle. The objective of this experiment was to determine the effects of dose and duration of ractopamine hydrochloride (RH) 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 3 RH doses (0, 300, or 400 mg∙steer -1 ∙d -1 ) fed for 3 durations (28, 35, or 42 d). Holstein steers ( n = 855; initial body weight [BW] = 448 ± 37 kg) were blocked by BW and randomly allocated to 1 of 9 pens (15 blocks; 9 dose × duration treatment combinations) approximately 72 d before harvest. Weekly pen weights, chute temperament scores, 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 and slice shear force (SSF) was determined on one steak selected from each side of the carcass after aging for 14 or 21 d. For feedlot performance, carcass characteristics, and SSF, no dose × duration interactions were observed ( P ≥ 0.11). With increasing RH dose, average daily gain (ADG) and gain-to-feed ratio (G:F) increased linearly ( P ≤ 0.01), whereas BW gain increased linearly with RH dose and duration ( P ≤ 0.01). Hot carcass weight ( P = 0.02) and longissimus muscle (LM) area ( P ≤ 0.01) increased linearly with increasing RH dose. The percentage of carcasses in the USDA Yield Grade 2 category increased linearly ( P ≤ 0.01) and percentage of carcasses in the USDA Yield Grade 4 category tended ( P = 0.08) to decrease linearly as RH dose increased. In the 14-d aged steaks, the percentage of steaks with SSF ≤ 15.3 kg decreased linearly ( P ≤ 0.01), whereas the percentage of steaks with ≥20.0 kg SSF increased linearly ( P ≤ 0.01) with increasing RH dose. After 21-d aging, there was a tendency ( P = 0.06) for a greater percentage of steaks from steers fed RH to have SSF ≥ 20.0 kg (2% of total steaks), 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) scores were not affected by feeding RH. Increasing the dose of RH (300 or 400 mg∙steer -1 ∙d -1 ) fed for 28 to 42 d before harvest increased ADG, G:F, hot carcass weight, and LM area when fed to Holstein steers with no negative effects on behavior or mobility. The percentage of steaks classified as not tender improved when steaks were aged for 21 d from steers treated with RH. (© The Author(s) 2019. Published by Oxford University Press on behalf of the American Society of Animal Science.)
Databáze:	MEDLINE
Externí odkaz:	Zobrazit plný text záznamu