A review of bloat in feedlot cattle.

Improvements in feedlot management practices and the use of various feed additives have reduced, but not eliminated, the occurrence of bloat in feedlot cattle. Feedlot bloat reduces the profitability of production by compromising animal performance and more directly by causing fatalities. In feedlots, bloat is associated with the ingestion of large amounts of rapidly fermented cereal grain and destabilization of the microbial populations of the rumen. An abundance of rapidly fermented carbohydrate allows acid-tolerant bacteria (e.g., Streptococcus bovis and Lactobacillus spp.) to proliferate and produce excessive quantities of fermentation acids. As a result, ruminal pH becomes exceedingly low, and this impairs rumen motility. Further, the excessive production of mucopolysaccharide or "slime" increases the viscosity of ruminal fluid and stabilizes the foam implicated in frothy feedlot bloat. Although protocols have been developed to treat feedlot bloat, the most profitable approach is to use management strategies to reduce its likelihood. Amount of roughage, grain processing techniques, selection of cereal grain (e.g., corn, barley, and wheat), dietary adaptation periods, and various additives (e.g., ionophores) can influence the occurrence of bloat in feedlot cattle. Successful management of these factors depends on a thorough understanding of the behavioral, dietary, and microbial events that precipitate bloat in feedlot cattle.