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
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2018-04-18
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Abstract
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.
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Beef cattle, Saccharomyces cerevisiae, yeast, rumen, pH, ionophore, bacteriophage, heat stress