Feeding crude glycerin decreases fecal shedding of E. coli O157:H7 in growing cattle

Abstract

Crude glycerin is a byproduct of ethanol production and is used as a carbohydrate source for cattle feed. Glycerin levels in previous studies have ranged from 0 to 20% of diet dry matter, and concentrations of 8% or less generally improve feedlot performance. At even low levels of glycerin, however, the activity of cellulolytic bacteria is depressed, ultimately leading to poorer fiber digestion. This observation suggests that glycerin may affect a specific population of bacteria in the gut. Crude glycerin can account for 8 to 10% of the weight of dried distillers grains with solubles, because it is one of the primary end-products when yeast ferments sugars to produce ethanol. Addition of 25% dried distillers grains with solubles to a feedlot diet increased the prevalence of Escherichia coli O157:H7 in feces of cattle. These observations led us to question whether glycerin might be the component of distillers grains responsible for the increases in prevalence of E. coli O157:H7 that often are observed in cattle fed distillers grains. To address this question, we added glycerin to diets of growing cattle and subsequently evaluated fecal shedding of E. coli O157:H7.