Managing Acidosis in Feedlot Cattle

Abstract

The cattle feeding business in the United States has evolved to an intensively managed system using grains as the primary source of energy. Grain feeding is common throughout the cattle feeding regions of the United States because the cost per unit of energy is often cheaper with grain compared with other feedstuffs available for beef cattle. In addition, grains are easier to store, handle, process, mix and deliver in rations compared with bulky, lower energy forage type feedstuffs. Consumers also prefer the taste and flavor of grain-fed beef compared with other alternatives.

Acidosis is one of the most important nutritional disorders in feedlot cattle today and is caused by a rapid production and absorption of organic acids and endotoxins from the rumen when cattle over consume grain (starch) or sugar in a short period of time. Acidosis is an array of stresses and is not confined to a single symptom such as ruminal pH. The previous definition is a collective term for several associated facets and includes the effects of organic acid production, ruminal pH, salivary flow, rate of passage, starch fermentation, feed intake and others. Ruminal acidosis often leads to metabolic acidosis in feedlot cattle. Acidosis is difficult to measure and diagnose in feedlot cattle. Even in metabolism studies designed to measure the effects of acidosis, it is difficult to research because as ruminal pH declines, cattle adjust by decreasing feed intake and altering their consumption patterns to help diminish the deleterious effects of acidosis.

Acidosis is not one disorder, but a continuum of degrees. Effects of acidosis can be slight as a .25 lb/ day decrease in feed intake, or as severe as the death of an animal. Brent² attributed founder, polioencephalomalcia (PEM) and ruminitis to acidosis in feedlot cattle. Sudden death syndrome, reduced feed intake, reduced absorption, liver abscesses, grain bloat and clostridial infections have been added to the list of acidosis related problems. Acidosis is not the only nutritional disorder that can occur in beef cattle fed high-grain diets, but may be a contributing factor to many of the diagnosed nutritional disorders that are currently observed in feedlot cattle. Many of the management recommendations that feedlot nutritionists make on a daily basis are to reduce the incidence and severity of acidosis. Because acidosis is not simply one disorder we generally separate acidosis into acute or subacute situations. The actual ruminal pH where subacute acidosis becomes acute is difficult to define and probably not very important. Additionally, the actual ruminal pH where an individual animal experiences subacute acidosis may be equally less important because of animal-to-animal variation.