摘要
Beef cattle production in the United States is faced with restricted access to previously used feed-grade antibiotics, deemed medically important, under the 2017 Veterinary Feed Directive. Suitable alternatives should be characterized and verified across different feeding scenarios to maintain production efficiency and implementation strategies should be investigated to ensure the best utilization of current technology.
In the first study, continuous versus rotational feeding of two products, monensin and bambermycin, were investigated to determine their effects on volatile fatty acids, potential activity of methane production, and rumen microbial populations of steers. We found no evidence to suggest that rotational feeding schemes were more effective than the continuous feeding of monensin and bambermycin or that rotational regimens delay microbial adaptation.
In the second study, the effects of supplemental yeast (ADY) in the diets of finishing steers were investigated under different environmental temperatures (TN = 18 ± 0.55°C or HS = 35 ± 0.55°C). We concluded that supplementing ADY in the diets of finishing steers improved digestibility, digestible energy, metabolizable energy, and mean ruminal pH under TN conditions, but not under extreme HS conditions, due to depressed intake and energetic demand.
In the third study, we observed the effects of supplementing ADY to feedlot steers (n = 120) fed for 164 days. Final treatment assignments were designated on d 70, followed by a 14 d dietary transition to a finishing diet, resulting in four treatment groups (Balaam’s design: two parallel groups and two cross-over groups). There is evidence to suggest that the addition of ADY in the diets of beef cattle during the dietary transition may aid in ruminal stabilization without affecting growth performance or carcass traits.
A fourth study was initiated to isolate and characterize bacteriophage that target hyper ammonia producing bacteria (HAB) in the rumen. HAB had poor bacterial lawn growth to detect phage plaques. Sequential transfer methods of Félix d'Hérelle are recommended to identify phage presence on these obligately anaerobic bacteria. Naturally occurring antimicrobial substances in environmental samples may have interfering effects. Future phage work should look to high impact bacteria that cause easily measurable losses to truly understand efficacy.
摘要译文
根据2017年的兽医饲料指令，美国面临牛奶的产量面临的限制性获取先前使用的饲料级抗生素。应在不同的喂食方案中对合适的替代方案进行表征和验证，以维持生产效率，并应研究实施策略，以确保最佳利用当前技术。在第一项研究中，研究了两种产物的连续旋转摄食，即Monensin和Bambermycin，以确定它们对挥发性脂肪酸的影响，甲烷产生的潜在活性以及管rembobial的乳头微生物种群。我们没有发现证据表明，旋转喂养方案比Monensin和Bambermycin的连续喂养或旋转方案延迟微生物适应性更有效。在第二项研究中，在不同的环境温度（TN = 18±0.55°C或HS = 35±0.55°C）下研究了补充酵母（ADY）在整理蒸汽饮食中的影响。我们得出的结论是，补充ADY在饮食饮食中的补充可提高消化率，可消化能，可移植能量，可代谢能量和在TN条件下的平均瘤胃pH，但在极端HS条件下，由于摄入量降低和能量性的需求而不是在极端的HS条件下。在第三项研究中，我们观察到将ADY补充为饲喂饲养场（n = 120）的影响164天。最终的治疗分配在D 70上指定，然后在饮食饮食中进行14 d过渡，导致四个治疗组（Balaam的设计：两个平行组和两个交叉组）。有证据表明，在饮食过渡期间，在肉牛饮食中加入ADY可能有助于瘤胃稳定，而不会影响生长表现或car体性状。开始了第四项研究，以分离并表征预噬细胞，该噬菌体靶向瘤胃中产生细菌（HAB）的超含量。HAB的细菌草坪生长较差，可以检测噬菌体斑块。建议使用FélixD'Hérelle的顺序转移方法来确定在这些有义的厌氧细菌上存在噬菌体的存在。环境样品中天然存在的抗菌物质可能具有干扰作用。未来的噬菌体工作应该考虑高影响细菌，从而造成易于测量的损失，以真正了解疗效。
Crossland, Whitney Lynn. Efficacy of Feed-Grade Antibiotics, Antibiotic Alternatives and the Impact of Thermal Stress on the Ruminal Microbiome, Ruminal Fermentation, Feedlot Performance, Feeding Behavior, and Carcass Characteristics of Beef Cattle[D]. US: Texas A&M University, 2018