Avoiding and Treating Grain Overload

Grain overload, also known as “Lactic Acidosis” or “Acute Carbohydrate Engorgement”, is a condition experienced by ruminants such as cattle, sheep and goats. Wild ruminants such as elk and deer appear to be more susceptible to this condition than traditional livestock species.

Acidosis usually occurs when animals have consumed large quantities of cereal grains or other sources of readily fermentable starch, or have had their diet suddenly switched from a high roughage diet to a high concentrate diet. It will usually manifest itself in the herd in one of two ways – an acute case will usually be terminal, while milder cases can be turned around. There is also the possibility that some of the affected animals will be more susceptible to secondary infections.

Acidosis is caused by an increase in lactic acid-producing bacteria in the rumen and the rapid production of lactic acid in both the d- and l- forms (these are the same chemical formula but have different rotational movement). It commonly occurs when there is a sudden change in diet, or when animals gain access to grain in large quantities. However, animals that are maintained on a high energy ration may normally be in a marginal state of acidosis due to the formation of lactic acid by the rumen bacterial flora. Therefore, ingredient changes, poor mixing of grains in the ration, or faulty feeding can produce acute acidosis in your deer.

Treatment must begin as soon as it is realized that an animal has eaten more than a normal amount (as little as half again as much) of grain or other sources of readily fermentable starch. The longer the treatment is delayed, the more difficult it is to reverse the progressive chain of events that will end in death in 2 to 4 days.

The underlying problem is the rapid fermentation of starch in the rumen with the resultant production of lactic acid. The lactic acid is picked up by the blood stream in amounts that are high enough to generally disrupt normal body chemistry. Lactic acid can also pool in joints and heavily worked muscles resulting in severe tendonitis, arthritis and lameness. It has also been suggested, that very acid conditions in the rumen may damage the lining of the mucous membrane, allowing bacterial to enter the blood stream and reach the liver, injuring this organ as well.

Usually the greedy feeders are the first to be affected. Symptoms comprise of staggering and apparent blindness, subnormal or normal body temperatures. This will usually be followed in 24 to 48 hours by recumbency, and finally coma and death. A profuse diarrhea may develop in later stages. Milder cases can recover when the high grain or high concentrate ration is removed, and extra roughage is provided.

The severity of the signs depend largely upon the amount of cereal grains or concentrates eaten. In the first few hours, a full rumen and restlessness may be all that is seen. There are mild cases, that do not progress beyond simple indigestion. However, in severe cases there may be evidence of extreme agitation and some pain (crying and getting up and down). The animal will often stagger and even appear blind. Their appetite will decrease dramatically during the first day as will rumen contractions. The feces may become soft.

The temperature of the deer will become sub-normal unless the animal is exposed to the hot sun. As the lactic acid level in the blood and body fluids increases, circulatory collapse or shock will begin; this will increase the heart rate. Animals with a heart rate of less than 100 are more likely to respond to treatment than those with a heart rate of 120-140 or higher. Respiration rate increases and breathing becomes shallow, diarrhea usually develop and is profuse.

The excess lactic acid in the rumen causes a large amount of fluid to be transported into the rumen. This process dehydrates the body and is detectable by an increase in the hematocrit reading (percentage of red blood cells in the whole body). This dehydration in combination with acidosis can cause circulatory collapse. This is best detected clinically by a paling of the mucous membranes, a fast heart but barely perceptible pulse. The rumen may feel full and doughy; if less grain was consumed, it may feel resilient because of increased fluid and gas. The rumen will have no contractions but one may hear a lot of gas rising through the fluid. Usually after two days the animal will lie down and not voluntarily get up.

The color of the mucous membrane of the eyes (vulva or penal sheath) should be observed early and regularly for evidence that the normal healthy pink is changing to pale pink or to white. If the mucous membranes are becoming pale, and the heart rate is above normal range, or if the animal is becoming depressed, or if it staggers slightly, or is showing evidence of pain, a veterinarian should personally evaluate and treat your animals.

In moderate cases, drenching or dosing 50 grams of magnesium hydroxide or magnesium oxide in a liter of warm water per 70 kg of body weight will work. In more severe cases, where the animal is still standing and the rumen pH is 5 to 6, a large stomach tube may be passed into the rumen. The rumen is washed with 10 to 15 irrigations. Tepid water is pumped in until obvious rumen distension occurs; then the rumen is allowed to empty by gravity. It is not enough to retrieve the water pumped in as any remaining grain must be washed out.

Systemic acidosis is combated with oral or intravenous fluid administration. Five percent sodium bicarbonate is given intravenously for severe acidosis at the rate of 500 ml per 100 lbs of body weight over a period of 30 minutes. This is followed by 1.3% sodium bicarbonate at the rate of 65 ml per lb of body weight over the next 6 to 12 hours. In severe cases, where the animal is down and in shock, the only life-saving procedure may be surgical removal of the grain from the rumen. This is a high-risk procedure, because of the already extremely bad condition of the animal. In cases that progress that far, there is also a high possibility of severe fungal rumenitis developing in 3 to 5 days. The owner should realize that surgery is much more apt to be successful earlier in the course of the disease at a time when conservative treatment still has a chance to work. The owner, with the advice of the veterinarian must decide the degree of acceptable risk.

Under most management systems, grain overload results from an over- consumption of grains or concentrates. It is advisable that rations for your deer should not contain a total cereal grain content higher than 35%. When changing a ration from one manufacturer to another, or even from the same manufacturer, changes should always be made slowly. Generally, it should take you 30 days to change from one feed to another by increasing the level of the new feed by 10% every three days. Always make sure that your animals have access to good quality pasture and forage as well as their regular rations.

By Brett Oliver-Lyons