Acidosis - Grain Poisoning

120 Beef Breeder MANUAL

4.5.6. Acidosis - Grain Poisoning

Acidosis, or grain poisoning, is a debilitating nutritional condition that results from the accumulation of large quantities of lactic acid arising from the fermentation of grains that are high in rapidly fermentable carbohydrates. Wheat, triticale, rye, barley and oats are in that order the most likely grains to cause acidosis. It can also occur in high quality diets that are low in efective ibre. Although it is not strictly a disease, it can have signiicant impacts on the herd, particularly where breeding cows and weaner cattle are fed grain diets during winter, calves are fed grain as a weaning supplement, or cattle are fed inishing diets with very high levels of grain. Acidosis commonly occurs when cattle that are not adapted to grain diets are irst given access to the grain. During the fermentation of grain by rumen microorganisms, lactic acid is produced. An excess of lactic acid afects the animal by; • Decreasing the numbers of useful bacteria in the rumen and increasing the amount of acid-producing bacteria causing further build-up of acid in the rumen • Causing rumen contractions to cease • Causing dehydration by drawing luid into the rumen from the tissues and blood • Causing the blood to become more acidic, resulting in heart failure, kidney failure and death • Damaging the rumen wall and enabling fungal or bacterial invasion of the body. This can result in peritonitis or liver abscess even up to a week after grain poisoning • Laminitis; a painful inlammation of the hoof, may occur, resulting in severe lameness. Fortunately, some species of bacteria that are normally resident in the rumen are able to utilise lactic acid and prevent excess lactic acid build-up, but unless grain is present in the diet, they remain only a minor component of the rumen micro-lora. Consequently, grain needs to be introduced gradually over a period of time to allow the lactic acid utilising bacteria to build up in numbers to a level where they can cope with the rapid production of lactic acid by other microbes in the rumen. Other instances where acidosis may occur include when a sudden increase in the quantity of grain is fed and excessive quantities are consumed, where a change in grain type or concentrate is fed, and as a result of an inadequate consumption of efective ibre. It has also been observed where animals have had accidental access to grain storage areas, or split grains. Cattle may sufer either of two forms of acidosis; acute rapid onset and chronic Table 4.5. Where cattle sufer acute acidosis, unless intervention is applied immediately upon observing afected animals, they will die from the efects of the condition. Chronic sub-acute acidosis may persist for an extended period, and although may not cause the death of the animals, they will sufer production losses by going ‘of-feed’ for periods of time when they are afected. Prevention Prevention of acidosis requires a multi-factorial approach to manage the inherent risk of high grain, low-ibre diets. 1. The gradual introduction of high risk feeds to cattle over a period of at least 14 days or longer is the most efective way to ensure that the rumen microorganisms adapt to the grain in the diet 2. Supplementary feeding with neutralising agents rumen bufers can also be used to further reduce the risk of acidosis. However, using bufers alone and without other preventative measures is not an efective way to prevent the condition. Commonly used rumen bufers include; • Sodium bicarbonate at 0.75 to 1.5 ww • Magnesium oxide at 0.5 to 0.975 ww plus sodium bicarbonate • Calcium carbonate at 1-2 ww, barley or triticale or 3 ww wheat 3. Adding ibre to the diet to promote rumination and salivabicarbonate production by the animal 4. Feeding cattle on a daily basis, or twice daily particularly during very cold weather see Section 3.7.1 will help cattle perform better than those fed irregularly, as it further limits the chances of grain poisoning 121 Cold Winter Climates 5. Total mixed rations can assist in the prevention of acidosis by providing a balanced ration containing ibre and grain. Faecal consistency should be monitored daily to identify potential problems as they develop. Treatment Cattle afected by grain poisoning should be removed from the herd and placed on a ‘recovery’ diet. This involves removing access to grain and providing good quality hay until the animal recovers and is usually efective for animals with mild cases. Feedlot animals that are scouring can be temporarily changed to a ration 20–25 lower in grain content for 2 to 3 days to see if their condition improves. In severe cases, where the animals are unable to stand and have abnormal body temperature, urgent veterinary assistance should be sought, and if unavailable, consideration should be given to humane destruction of the individual see Section 4.2.6. Table 4.5. Symptoms of cattle with acidosis grain poisoning. Acute Acidosis Chronic Acidosis Rumen contents become acidic, falling below 5.0 Reduction in rumen pH, and motility Excessive luid build-up within rumen and intestinal contents lead to a distension of the abdomen Faeces may appear as diarrhea Fig. 4.5, foamy, with gas bubbles, and contain undigested ibre or grain Loss of appetite, depression, isolation, panting, dehydration Reduction in rumination cud chewing Laminitis lameness Reduced feed eiciency Diarrhea Daily variation in feed intake is high Death Reduction in average daily growth rates 122 Beef Breeder MANUAL

4.5.7. Bloat