Effect of feedlot management system on response to ractopamine-HCl in yearling steers.

Two experiments evaluated the effects of conventional and natural feedlot management systems (MS) on ractopamine-HCl (RAC) response in yearling steers. Feedlot performance, carcass characteristics, skeletal muscle gene expression, and circulating IGF-I concentrations were measured. The conventional system included a combined trenbolone acetate and estradiol implant, Revalor-S (IMP), as well as monensin-tylosin feed additives (IA). Treatments were arranged in a 2 x 2 factorial and included: 1) natural (NAT): no IMP-no IA, no RAC; 2) natural plus (NAT+): no IMP-no IA, RAC; 3) conventional (CON): IMP-IA, no RAC; and 4) conventional plus (CON+): IMP-IA, RAC. In Exp. 1, one hundred twenty crossbred steers (initial BW = 400 +/- 26 kg) were allotted randomly to treatment in a randomized complete block design (BW was blocking criteria); pen was the experimental unit. In Exp. 2, twenty-four individually fed crossbred steers (initial BW = 452 +/- 25 kg) were used in a randomized complete block design (BW was blocking criteria) and assigned to the same treatments as Exp. 1, with 6 steers/treatment. In Exp. 2, serum was harvested on d 0 and 31 and within the 28-d RAC feeding period, at d 0, 14, and 28. Longissimus biopsy samples were taken on d 0, 14, and 28 of the RAC feeding period for mRNA analysis of beta-adrenergic receptors and steady-state IGF-I mRNA. In Exp. 1, ADG, G:F, final BW, and HCW were greatest for CON+ (P < 0.01). During the final 37 d, RAC increased ADG (P = 0.05) and increased overall G:F (P = 0.02). Marbling score was reduced (P = 0.02), and yield grade was improved with RAC (P = 0.02), but RAC did not affect dressing percentage (P = 0.96) or HCW (P = 0.31). In Exp. 2, MS x RAC interactions were detected in ADG and G:F the last 28 d, overall ADG and overall G:F, final BW, and HCW (P < 0.01). Dressing percentage, yield grade, and marbling score were not altered by MS or RAC (P > 0.10). Circulating IGF-I concentration was increased on d 31 by the conventional MS, and concentration was greater throughout the study than NAT steers (P < 0.01). Circulating IGF-I concentrations were not changed by RAC (P = 0.49). Abundance of beta(1)-AR mRNA tended to increase (P = 0.09) with RAC, but RAC did not affect beta(2)-AR, beta(3)-AR, or IGF-I mRNA (P > 0.40). Management system did not affect beta(1)-AR, beta(2)-AR, beta(3)-AR, or IGF-I mRNA (P > 0.18), yet a trend (P = 0.06) for MS x RAC for beta(2)-AR mRNA was detected. These results indicate that response to RAC is affected by feedlot management practices.

[1]  J. Higgins,et al.  Effects of steroidal implantation and ractopamine-HCl on nitrogen retention, blood metabolites and skeletal muscle gene expression in Holstein steers. , 2007, Journal of animal physiology and animal nutrition.

[2]  B. Johnson,et al.  Response to ractopamine-HCl in heifers is altered by implant strategy across days on feed. , 2007, Journal of animal science.

[3]  J. Carter,et al.  Effect of ractopamine-hydrochloride and trenbolone acetate on longissimus muscle fiber area, diameter, and satellite cell numbers in cull beef cows. , 2007, Journal of animal science.

[4]  J. D. Tatum,et al.  Effects of ractopamine supplementation on growth performance and carcass characteristics of feedlot steers differing in biological type. , 2007, Journal of animal science.

[5]  G. L. Parsons,et al.  Response to ractopamine-hydrogen chloride is similar in yearling steers across days on feed. , 2007, Journal of animal science.

[6]  B. Johnson,et al.  Melengestrol acetate alters muscle cell proliferation in heifers and steers. , 2006, Journal of animal science.

[7]  D. Boggs,et al.  The effect of stage of growth and implant exposure on performance and carcass composition in steers. , 2005, Journal of animal science.

[8]  J. Drouillard,et al.  Effects of flax supplementation and a combined trenbolone acetate and estradiol implant on circulating insulin-like growth factor-I and muscle insulin-like growth factor-I messenger RNA levels in beef cattle. , 2003, Journal of animal science.

[9]  M. Pampusch,et al.  Time course of changes in growth factor mRNA levels in muscle of steroid-implanted and nonimplanted steers. , 2003, Journal of animal science.

[10]  D. A. Walker,et al.  Niche-Targeted vs Conventional Finishing Programs for Beef Steers , 2003 .

[11]  E. Falkenstein,et al.  Multiple actions of steroid hormones--a focus on rapid, nongenomic effects. , 2000, Pharmacological reviews.

[12]  J. D'mello,et al.  Phenethanolamine repartitioning agents. , 2000 .

[13]  B. Woodward,et al.  Comparison of conventional and organic beef production systems I. feedlot performance and production costs , 1999 .

[14]  B. Woodward,et al.  Comparison of conventional and organic beef production systems II. Carcass characteristics , 1999 .

[15]  A. Dicostanzo,et al.  Activation state of muscle satellite cells isolated from steers implanted with a combined trenbolone acetate and estradiol implant. , 1998, Journal of animal science.

[16]  M. Hathaway,et al.  Stimulation of circulating insulin-like growth factor I (IGF-I) and insulin-like growth factor binding proteins (IGFBP) due to administration of a combined trenbolone acetate and estradiol implant in feedlot cattle. , 1996, Journal of animal science.

[17]  B. Johnson,et al.  Effect of a combined trenbolone acetate and estradiol implant on feedlot performance, carcass characteristics, and carcass composition of feedlot steers. , 1996, Journal of animal science.

[18]  J. Oldham,et al.  The role of insulin-like growth factor I in clenbuterol-stimulated growth in growing lambs. , 1995, Journal of animal science.

[19]  W. Stroup,et al.  Effect of monensin and monensin and tylosin combination on feed intake variation of feedlot steers. , 1995, Journal of animal science.

[20]  J. Craigon,et al.  Influence of diet and β-agonist administration on plasma concentrations of growth hormone and insulin-like growth factor-1 in young steers , 1993, British Journal of Nutrition.

[21]  R. E. Brown,et al.  Trenbolone acetate/estradiol combinations in feedlot steers: dose-response and implant carrier effects. , 1992, Journal of animal science.

[22]  P. Molenaar,et al.  Cimaterol reduces beta-adrenergic receptor density in rat skeletal muscles. , 1992, Journal of animal science.

[23]  A. Moloney,et al.  Effects of cimaterol administration on plasma concentrations of various hormones and metabolites in Friesian steers. , 1991, Domestic animal endocrinology.

[24]  D. Beermann,et al.  Temporal pattern of skeletal muscle changes in lambs fed cimaterol. , 1991, Domestic animal endocrinology.

[25]  D. Hunt,et al.  Use of trenbolone acetate and estradiol in intact and castrate male cattle: effects on growth, serum hormones, and carcass characteristics. , 1991, Journal of animal science.

[26]  M. Miller,et al.  Adipose tissue cellularity and muscle growth in young steers fed the beta-adrenergic agonist clenbuterol for 50 days and after 78 days of withdrawal. , 1990, Journal of animal science.

[27]  J. P. Fontenot,et al.  Implanting trenbolone acetate and estradiol in finishing beef steers , 1989 .

[28]  W. R. Butler,et al.  Cimaterol-induced muscle hypertrophy and altered endocrine status in lambs. , 1987, Journal of animal science.

[29]  D. Young,et al.  Effect of monensin and tylosin on average daily gain, feed efficiency and liver abscess incidence in feedlot cattle. , 1985, Journal of animal science.

[30]  R. H. Dalrymple,et al.  Use of a β-Agonist to Alter Fat and Muscle Deposition in Steers1, 2 , 1984 .

[31]  R. B. Young,et al.  Cellular aspects of muscle growth: myogenic cell proliferation. , 1979, Journal of animal science.

[32]  G. Newton,et al.  Effects of Feeding Monensin in Combination with Zeranol and Testosterone-Estradiol Implants for Growing and Finishing Heifers , 1976 .