Frothy bloat in ruminants: Cause, occurrence, and mitigation strategies

Abstract

A number of pasture and feedlot management practices and feed additives have reduced, but not eliminated the occurrence of frothy bloat in cattle. Bloat occurs as a result of complex interactions among the feed, rumen microbial populations and the host. Factors such as soluble protein levels in the feed, rates of feed digestion, bacterial slime production and digesta passage rates, all play a role in the likelihood of bloat. Practices that lower soluble protein levels and retard the rate of feed digestion can reduce the risk of bloat as can grazing alfalfa at advanced stages of maturity. Similarly, processing grain to an optimal particle size, inclusion of ionophores in the diet and allowing a period of adaptation during the transition from forage to grain diets lowers the incidence of feedlot bloat. Pluronic detergents which disperse the stable froth in the rumen can be effective in the treatment and prevention of both pasture and feedlot bloat. The sporadic and unpredictable nature of frothy bloat often makes it unrealistic for preventative measures to be applied to all animals at risk. Genetic engineering of condensed tannin containing, bloat-safe varieties of alfalfa and clover may eliminate the occurrence of bloat in cattle grazing these forages. Understanding the factors that regulate intake and contribute to bacterial slime production could provide additional insight into feedlot bloat. Comparing of the rumen microbial metagenomes and metatrascriptomes of bloated and non-bloated animals should provide a fresh perspective on the role of rumen microbial populations in bloat. The key to the successful prevention of frothy bloat lies in a thorough understanding of the feed, microbial and host factors involved in the condition.