Thompson A J, Smith Z K F, Corbin M J, Harper L B, Johnson B J
J Anim Sci. 2016 Dec;94(12):5341-5349. doi: 10.2527/jas.2016-0841.
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.
选用192头阉牛（体重=354±23.5千克），采用随机区组设计，评估离子载体和盐酸莱克多巴胺（RH）添加策略对生产性能和胴体特性的影响。将12个圈舍，每个圈舍4头阉牛，分配到以下各处理组：不添加任何物质的对照组（CON）、添加或不添加RH的丙酸拉沙洛西（12.1毫克/千克干物质）（分别为LPRH和LP），以及添加RH的莫能菌素钠（36.4毫克/千克干物质）（MSRH）。阉牛饲养151天，其中各处理组在最后32天按300毫克/（头·天）的剂量投喂RH（Actogain；硕腾公司，美国新泽西州弗洛勒姆帕克）。在此期间，LPRH处理组不再投喂拉沙洛西，因为尚未批准联合投喂。屠宰时，由训练有素的人员收集胴体数据，随后对腰大肌进行分析，采用沃纳-布拉茨勒剪切力（WBSF）评估嫩度。在添加RH之前，LP和LPRH的平均日增重（ADG）（P≤0.02）和料重比（G:F）（P<0.01）均高于CON，而MSRH处于中间水平。在最后32天，与所有其他处理组相比，MSRH改善了料重比（P≤0.02），且与未添加RH的对照组相比，ADG有增加趋势（P=0.05）。未添加RH的LP处理组阉牛在第151天的体重显著高于CON组（P=0.02），而两种添加RH的处理组均有提高末重的趋势（P≤0.09）。在整个饲养期，离子载体提高了ADG（P≤0.03）和料重比（P<0.01），尽管在最后32天，添加LP的阉牛干物质采食量高于两种添加RH的处理组（P≤0.01），但在151天的试验期内，各处理组的采食量相似。未添加RH的LP处理组阉牛的胴体重高于CON组（P=0.04），前者的热胴体重平均比后者多12千克。添加RH使MSRH处理组阉牛的腰大肌面积增加（P=0.03），且使接受LPRH处理的阉牛腰大肌面积有增加趋势（P=0.07）。宰后7天，MSRH处理组阉牛的背最长肌牛排的WBSF值高于CON组（P=0.04），宰后28天，其WBSF值高于LPRH处理组的牛排（P=0.03）。其他胴体指标和WBSF测量结果在各处理组间相似。本研究结果表明：不添加RH的LP添加处理可能产生与β-激动剂给药相似的生产性能和胴体反应。这些结果还表明，在整个饲养期，饲喂LP的阉牛的生产性能和胴体特性与饲喂莫能菌素的阉牛相似。
