monensin and ractopamine

One hundred ninety-two steers (BW = 354 ± 23.5 kg) were used in a randomized block design to evaluate the effects of ionophore and ractopamine hydrochloride (RH) supplementation strategies on performance and carcass characteristics. Twelve pens of 4 steers were assigned to each of the following treatments: unsupplemented control (CON), laidlomycin propionate (12.1 mg/kg DM) with or without RH (LPRH and LP, respectively), and monensin sodium (36.4 mg/kg DM) with RH (MSRH). Steers were fed for 151 d, of which respective treatments received RH (Actogain; Zoetis, Florham Park, NJ) at a rate of 300 mg/(animal · d) for the final 32 d. Laidlomycin was removed from the LPRH treatment during this period, as no combination feeding has been approved. Upon harvest, carcass data were collected by trained personnel, and subsequent analysis of the LM was conducted to estimate tenderness using Warner-Bratzler shear force (WBSF). Prior to RH supplementation, both LP and LPRH had greater ADG ( ≤ 0.02) and G:F ( < 0.01) than CON, whereas MSRH was intermediate. During the final 32 d, MSRH improved G:F ( ≤ 0.02) compared to all other treatments and tended to increase ADG over unsupplemented controls ( = 0.05). Cattle receiving LP without RH had significantly greater BW at d 151 than CON ( = 0.02), whereas both RH treatments tended to improve final BW ( ≤ 0.09). Ionophores improved ADG ( ≤ 0.03) and G:F ( < 0.01) for the entire feeding period, and although LP-supplemented cattle had greater DMI for the final 32 d than both RH treatments ( ≤ 0.01), intakes for the 151-d trial were similar among treatments. Carcass weights were greater ( = 0.04) in cattle fed LP with no RH than CON, where cattle yielded an average of 12 kg more HCW. Ractopamine increased LM area in MSRH-supplemented cattle ( = 0.03) and tended to increase LM area for steers receiving LPRH ( = 0.07). Longissimus steaks of MSRH-supplemented cattle had greater WBSF values than CON ( = 0.04) after 7 d of postmortem aging and greater WBSF values than LPRH steaks after 28 d ( = 0.03). All other carcass and WBSF measurements were similar among treatments. The results of this study indicate that LP supplementation without RH may yield a performance similar to and carcass responses associated with the administration of a β-agonist. These results also suggest that performance and carcass characteristics for cattle fed LP are similar to those of cattle fed monensin throughout the feeding period.

Topics: Adrenergic beta-Agonists; Animal Feed; Animal Nutritional Physiological Phenomena; Animals; Body Composition; Cattle; Diet; Dietary Supplements; Ionophores; Male; Monensin; Phenethylamines; Trimethylsilyl Compounds

The term sustainable has many meanings, but in agriculture it generally refers to some balance between environmental, social, and economic goals. The objective of this project was to quantify inputs and outputs to assess the sustainability implications of 2 feedlot cattle management systems: Never Ever 3 (NE3) and a conventional (CON) system using metabolic modifiers. Angus-cross steers (n=104) were stratified by BW (337 kg ± 17) and randomly assigned to 4 pens per treatment group. The NE3 cattle received no feed additives or implants, whereas CON were implanted with 100 mg of trenbolone acetate and 14 mg of estradiol benzoate on d 1 and 70, and were additionally fed monensin [330 mg/(animal·d)] and tylosin phosphate [90 mg/(animal·d)] in their ration throughout the course of the study, and ractopamine hydrochloride at 254 mg/(animal·d) for the last 29 d on feed. Cattle were shipped on a constant average pen weight basis (596 kg ± 32 BW). The CON cattle had greater ADG (1.81 vs. 1.35 kg, P < 0.01) and were on feed fewer days (146 vs. 188 d, P < 0.01) than the NE3 cattle. No significant differences were observed in HCW (P = 0.072) or dressing percentage (P=0.62) between treatments (P > 0.05); however, CON carcasses averaged larger ribeye area (87 vs. 80 cm(2), P < 0.01), greater Warner-Bratzler shear force measurement (WBSF; 3.46 vs. 3.19 kg, P < 0.01), and smaller USDA marbling score (5.4 vs. 6.2, P < 0.01), and less backfat thickness (1.64 vs. 1.84 cm, P < 0.05) and yield grade (3.38 vs. 3.95, P < 0.01) than NE3 carcasses. Overall, CON cattle consumed 393 kg less DM in the feedlot (1,250 vs. 1,643 kg; P < 0.05). No treatment effects were observed for daily methane (CH(4); P=0.62) or nitrous oxide (N(2)O; P=0.7) emissions per steer. Assuming a constant emission rate on a DMI basis throughout the course of the feedlot trial, CON feedlot management resulted in a 31% decrease in emissions per finished steer compared with NE3 management. Expressing CH(4) emissions on a carbon dioxide equivalent (CO(2)-eq) basis revealed a 1.10-kg CO(2)-eq difference per kilogram BW gain (5.02 kg of NE3 vs. 3.92 kg of CON) between the 2 feedlot management systems. Although the metabolic modifiers resulted in additional costs for the CON treatment group, the cost per kilogram of feedlot BW gain was significantly less ($1.12/kg vs. $1.35/kg; P < 0.05) than NE3. Both production systems satisfied some sustainability criteria, although neither concurrently fulfilled all of the envi

Topics: Air Pollutants; Animal Feed; Animal Nutritional Physiological Phenomena; Animals; Body Composition; Cattle; Diet; Drug Implants; Estradiol; Greenhouse Effect; Growth Substances; Methane; Monensin; Phenethylamines; Trenbolone Acetate; Tylosin

Inclusion of distillers grains (DG) in cattle diets has been shown to increase fecal shedding of Escherichia coli O157:H7. It is hypothesized that altered gut fermentation by DG may be responsible for the positive association. Therefore, feed additives affecting ruminal or hindgut fermentation of DG also may affect fecal shedding of E. coli O157:H7. The objectives of the study were to evaluate effects of monensin (33 or 44 mg/kg of DM), supplemental urea (0, 0.35, or 0.70% of DM), and ractopamine (0 or 200 mg/steer daily administered during the last 42 d of finishing) in a steam-flaked corn grain-based diet containing 30% wet sorghum DG on fecal shedding of E. coli O157:H7. Seven hundred twenty crossbred beef steers, housed in 48 pens (15 steers/pen), were assigned to dietary treatments in a randomized complete block design with a 2 × 3 × 2 factorial treatment arrangement. Fresh pen floor fecal samples (10 per/pen) were collected every 2 wk for 14 wk (July through November) and cultured for E. coli O157:H7. Isolation of E. coli O157:H7 was by selective enrichment of fecal samples in an enrichment broth, immunomagnetic separation, followed by plating onto a selective medium. Samples that yielded sorbitol-negative colonies, which were positive for indole production, O157 antigen agglutination, and contained rfbE, fliC, and stx2 were considered positive for E. coli O157:H7. Fecal prevalence data were analyzed as repeated measures using negative binomial regression to examine effects and interactions of sampling day, urea, monensin, and ractopamine. Mean fecal prevalence of E. coli O157:H7 was 7.6% and ranged from 1.6 to 23.6%. Cattle fed monensin at 44 mg/kg of feed had less (P = 0.05) fecal E. coli O157:H7 prevalence than cattle fed 33 mg/kg (4.3 vs. 6.8%). Although the reason for the reduction is not known, it is likely because of changes in the microbial ecosystem induced by the greater amount of monensin in the hindgut. Supplemental urea at 0.35 or 0.70% had no effect (P = 0.87) on fecal shedding of E. coli O157:H7. Fecal prevalence of E. coli O157:H7 were 5.3, 5.7, and 5.9% for groups fed 0, 0.35, and 0.7% urea, respectively. The inclusion of ractopamine at 0 or 200 mg/(animal•d) had no effect (P = 0.89) on fecal prevalence of E. coli O157:H7 (4.4 vs. 4.0%). Additional research is needed to confirm the reduction in fecal shedding of E. coli O157:H7 in cattle fed monensin at 44 mg/kg of feed compared with cattle fed 33 mg/kg of feed.

Topics: Animal Feed; Animals; Cattle; Diet; Dietary Supplements; Escherichia coli O157; Feces; Growth Substances; Monensin; Phenethylamines; Urea