Risk for Ruminai Acidosis During Finishing

摘要

Finishing beef cattle are fed highly fermentable diets to provide adequate dietary energy and metabolizable protein supply while maximizing the gain-to-feed ratio. These diets increase the rate and extent of fermentation within the rumen and consequently the rate of acid production. Excessive rates of acid production reduce ruminai pH, and increase osmolality and the concentration of microbial associated molecular patterns; all of which may compromise the integrity of the ruminai and intestinal epithelium. Historically, researchers have used low ruminai pH as the single indicator for ruminai acidosis. As a result, numerous reports suggest that feedlot cattle are at high risk for ruminai acidosis during the transition from a backgrounding to finishing diet and throughout the finishing period. However, when evaluating the prevalence, severity, and risk factors for ruminai acidosis in feedlot cattle under commercial settings, we have reported that under well managed conditions, the prevalence is highbut severity for ruminai acidosis is low during the diet transition period in group fed cattle. That said, our data suggest that the terminal phase of the finishing period may be a time with greater risk potentially due to environmental conditions or thesensitivity of cattle themselves to ruminai acidosis as they experience repeated bouts of excessive ruminai fermentation and increased body fat content. Overall, the severity of ruminai acidosis during finishing is quite low under well-managed conditions. While ruminai pH is relatively easy to measure, conditions related to ruminai acidosis that lead to the secondary disorders observed in finishing cattle (ruminitis, liver abscesses, and laminitis) have eluded researchers. We recently reported that cattle with ruminai and/or liver pathology at slaughter had greater concentrations of circulating acute phase proteins and spent more time with ruminai pH < 5.2 during the finishing period. Thus, our data suggest that a combination of severely depressed lowpH and increased antigen concentration may help predict cattle at risk for secondary disorders arising from ruminai acidosis.