Effect of preslaughter feeding and ractopamine hydrochloride supplementation on growth performance, carcass characteristics, and end product quality in market dairy cows

• Published in: Journal of animal science 2009-07, Vol.87 (7), p.2400-2408
• Main Authors: Allen, J.D, Ahola, J.K, Chahine, M, Szasz, J.I, Hunt, C.W, Schneider, C.S, Murdoch, G.K, Hill, R.A
• Format: Article
• Language: English
• Subjects: Adrenergic beta-Agonists - pharmacology; Aging - physiology; animal age; Animal Feed - analysis; Animal Nutritional Physiological Phenomena; Animal productions; Animals; beef; beef quality; Biological and medical sciences; Body Composition - drug effects; body condition; body weight; carcass characteristics; carcass grading; carcass weight; Cattle - growth & development; cow feeding; culling (animals); dairy cows; Dairying; Diet - veterinary; Dietary Supplements; dressing percentage; dry matter intake; feed additives; feed concentrates; feedlots; Female; finishing; food animals; Food industries; Fundamental and applied biological sciences. Psychology; locomotion; marbling; Meat - standards; Meat and meat product industries; meat grades; meat quality; meat tenderness; Muscle, Skeletal - physiology; Phenethylamines - pharmacology; ractopamine hydrochloride; sensory properties; subcutaneous fat; Taste; Terrestrial animal productions; Vertebrates
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2008-1630

An experiment was conducted in market dairy cows to determine the effect of feeding time and ractopamine hydrochloride (RAC) on growth performance, carcass characteristics, and end product quality. In 3 replicates, 9 Holstein cows per replicate (n = 27; 659 ± 25.3 kg initial BW) culled from 3 dairies were randomly assigned to 3 treatments: 1) slaughter immediately (control), 2) feed for 90 d (NoR), or 3) feed for 90 d with RAC (312 mg·cow⁻¹·d⁻¹) for the final 32 d (RAC). On d 0, NoR and RAC cows were placed in individual pens and fed a high concentrate diet (86% concentrate, DM basis) for 90 d before slaughter. All cows were subjectively scored for BCS and locomotion score on d 0, and NoR and RAC cows were evaluated again after 90 d. Individual DMI was recorded daily throughout the trial, and BW was collected every 14 d. Age and age x treatment did not affect (P > 0.05) any of the traits evaluated in this study. When cows fed for 90 d (NoR and RAC combined) were compared with nonfed controls, fed cows had greater (P < 0.001) final BCS, BW and HCW, lower (P < 0.001) final locomotion score, and greater (P < 0.03) dressing percentage, external fat thickness, and marbling score. Fed cows also tended to have more desirable yield grade (P = 0.08), ribeye area (P = 0.11), fat color (P = 0.09), lean maturity (P = 0.06), and quality grade (P = 0.09) compared with control cows. Warner-Bratzler shear force was not affected (P = 0.23) by feeding. However, a 12-member trained sensory panel revealed that fed cow carcasses had more desirable (P < 0.04) tenderness, juiciness, and overall acceptability than control cow carcasses. Flavor intensity also tended (P = 0.10) to be more desirable for fed vs. control cows. No difference (P > 0.10) in off-flavor was detected among treatments. Finally, there was no effect (P > 0.10) of RAC on growth performance, carcass characteristics, or end product quality. In conclusion, feeding a high concentrate diet for 90 d improved important live animal, carcass, and end product characteristics related to the quality and palatability of beef from market dairy cows; however, no effect of RAC supplementation was observed.