Effects of ractopamine hydrochloride and zilpaterol hydrochloride supplementation on carcass cutability of calf-fed Holstein steers

• Published in: Journal of animal science 2014-01, Vol.92 (1), p.369-375
• Main Authors: Howard, S T, Woerner, D R, Vote, D J, Scanga, J A, Acheson, R J, Chapman, P L, Bryant, T C, Tatum, J D, Belk, K E
• Format: Article
• Language: English
• Subjects: Adrenergic beta-Agonists - administration & dosage; Adrenergic beta-Agonists - metabolism; Animal Feed - analysis; Animals; Body Composition - drug effects; Cattle - physiology; Diet - veterinary; Dietary Supplements - analysis; Drug Implants - administration & dosage; Drug Implants - pharmacology; Estradiol - administration & dosage; Estradiol - analogs & derivatives; Estradiol - pharmacology; Male; Meat - analysis; Muscle, Skeletal - drug effects; Phenethylamines - administration & dosage; Phenethylamines - metabolism; Progesterone - administration & dosage; Progesterone - pharmacology; Trenbolone Acetate - administration & dosage; Trenbolone Acetate - pharmacology; Trimethylsilyl Compounds - administration & dosage; Trimethylsilyl Compounds - metabolism
• ISSN: 1525-3163
• DOI: 10.2527/jas.2013-7104

Effects of ractopamine hydrochloride (RH) and zilpaterol hydrochloride (ZH) on saleable yield of carcass sides from calf-fed Holstein steers were evaluated using steers implanted with a progesterone (100 mg) plus estradiol benzoate (10 mg) implant followed by a terminal trenbolone acetate (200 mg) plus estradiol (40 mg) implant. Steers were blocked by weight into pens (n = 32) randomly assigned to one of four treatments: control, RH fed at 300 mg•steer(-1)/d(-1) (RH 300) or RH fed at 400 mg•steer(-1)/d(-1) (RH 400) the final 31 d of finishing, and ZH fed at 60 to 90 mg•steer(-1)/d(-1) (7.56 g/ton on a 100% DM basis) for 21 d with a 5 d withdrawal before harvest. Eight to nine carcass sides were randomly selected from each pen; carcass sides with excessive hide pulls, fat pulls or bruises were avoided. Cutout data were collected within a commercial facility using plant personnel to fabricate sides at a rate of one every 3 to 4 min into items typically merchandised by the facility. All lean, fat and bone were weighed and summed back to total chilled side weight with a sensitivity of ± 2% to be included in the data set. Compared to controls, β-agonists increased saleable yield of whole-muscle cuts by 0.61%, 0.86% and 1.95% for RH 300, RH 400 and ZH, respectively (P < 0.05). Percent fat was less in carcasses from the ZH treatment compared to controls (P < 0.05); however, this difference was not observed between RH treatments and controls (P > 0.05). Percent bone was less in the ZH treatment due to increased muscle (P < 0.05). The percent of chilled side weight comprised of trimmings was unchanged between treatments, but on a 100% lean basis, RH 400 and ZH increased trim yields (P < 0.05). Analysis of saleable yield by primal showed a fundamental shift in growth and development. Beta-agonists caused a shift in proportion of saleable yield within individual primals, with a greater portion produced from the hindquarter relative to the forequarter, specifically in those muscles of the round (P < 0.05). Beta-agonists increased saleable yield, but these effects were not constant between all major primals. The cutout value gained by packers as a result of β-agonist use may be influenced more by reduced fatness and increased absolute weight if musculature is primarily increased in the lower priced cuts of the carcass.