Simple Indigestion in Ruminants

Almost any dietary factor that can alter the intraruminal environment can cause simple indigestion. The disease is common in hand-fed dairy and beef cattle because of variability in the quality and quantity of their feed. Dairy cattle may suddenly eat excessive quantities of highly palatable feeds such as corn or grass silage; beef cattle may eat excessive quantities of relatively indigestible, poor-quality roughage during winter. During drought, cattle and sheep may be forced to eat large quantities of poor-quality straw, bedding, or grain. Simple indigestion can result from suddenly changing the feed, using spoiled or frozen feeds, introducing urea to a ration, turning cattle onto a lush cereal grain pasture, or introducing feedlot cattle to a high-level grain ration.

Simple indigestion is usually associated with a sudden change in the pH of the ruminal contents, such as a decrease in ruminal pH due to rapid fermentation of ingested carbohydrates or an increase in ruminal pH due to forestomach hypomotility and putrefaction of ingested feed. It can also result from accumulation of excessive quantities of relatively indigestible feed that may physically impair rumen function. Multiple animals are usually simultaneously affected because simple indigestion has a nutritional basis, although the severity of the clinical signs can vary among animals.

Clinical signs depend on the type of animal affected and cause of the disorder. Overfeeding of silage causes anorexia and a moderate drop in milk production in dairy cattle. The rumen is usually full, firm, and doughy; primary contractions are decreased in rate or absent, but secondary contractions may be present although usually decreased in strength. Temperature, pulse, and respiration are normal. The feces are normal to firm in consistency but reduced in amount. Recovery usually is spontaneous within 24–48 hr.

Simple indigestion due to excessive feeding of grain results in anorexia and ruminal hypomotility to atony (stasis). The rumen is not necessarily full and may contain excessive fluid. The feces are usually soft to watery and foul smelling. The mechanism for diarrhea formation is uncertain but is most likely due to increased luminal osmolality as a result of the rapid degradation of ingested carbohydrates. The affected animal is bright and alert and usually begins to eat within 24 hr. A more severe digestive upset due to excessive feeding of grain is described as grain overload (see Grain Overload in Ruminants).

A diagnosis of simple indigestion is based on a history of an abrupt change in the nature or amount of the diet, multiple animals being affected, and most importantly the exclusion of other causes of forestomach dysfunction. The diagnosis is confirmed by collection and examination of ruminal fluid, which may have an abnormal pH (<6 or >7), decrease in the numbers and size of protozoa, or prolonged methylene blue reduction time (a measure of bacterial metabolic activity).

The systemic reaction and painful responses to deep palpation of the xiphoid in traumatic reticuloperitonitis are not seen. The history and the absence of ketonuria help eliminate clinical ketosis from consideration. The possibility of left displaced abomasum usually can be eliminated by simultaneous percussion and auscultation.

Vagal indigestion, abomasal volvulus, and cecocolic volvulus become more readily detectable as they progress. Grain overload is differentiated from simple indigestion by its greater severity and the pronounced fall in the pH of the rumen contents to <5.5.

Treatment is aimed at correcting the suspected dietary factors. Spontaneous recovery is usual when animals are fed a typical ruminant diet. Administration of ~20 L of warm water or saline via a stomach tube, followed by vigorous kneading of the rumen, may help restore rumen function in adult cattle. Magnesium hydroxide PO may be useful when excessive amounts of grain have been ingested, but magnesium hydroxide should only be administered to cattle documented to have low ruminal pH (<6); otherwise, excessive forestomach and systemic alkalinization can result. Purported rumenatorics (eg, nux vomica, ginger, tartar emetic, parasympathomimetics) are not recommended as ancillary treatments. If too much urea (see Nonprotein Nitrogen Poisoning) or protein has been ingested, vinegar (acetic acid) may be administered PO to return rumen pH to the normal range. If the number or activity of ruminal microbes is reduced, administration of 4–8 L of ruminal fluid from a healthy cow will help. (See also Ruminal Fluid Transfer.) Oral or intravenous electrolyte solutions may be needed to correct electrolyte and acid-base abnormalities, particularly in dehydrated cattle.