By Dr Keith Fletcher
Rochester Veterinary Practice
Recently we had to attend a case of grain overload in calves. Despite treatment, 15 out of 60 calves died — which once again highlights the potential for disaster if calves get access to excessive amounts of grain.
The main complication of grain overload is lactic acidosis. This is caused by bacteria in the rumen breaking down the carbohydrates in the grain to form lactic acid and other volatile fatty acids. The acid production lowers the pH of the rumen to a point where the microbes are killed and the rumen stops contracting and ceases to function.
A normal rumen has a pH of 7, whereas in acidosis the rumen pH is less than 5. High amounts of acids in the rumen have a tendency to draw water from the body, so causing the calf to become dehydrated. In severe cases of overload the calf will be off its feed, sunken-eyed, have diarrhoea and may be down and unable to rise.
These animals require urgent veterinary attention, and treatment involves giving bicarb as a drench and/or intravenously along with a number of supportive treatments. Best results are achieved when treatment is given early, while any delay increases the chances of irreparable damage to the rumen, and death. Those that survive may still have damaged rumens and may need a cud transfer to get fired up. Liver abscesses are another possible complication to rumenitis.
Feeding concentrates to calves has become commonplace in order to achieve today’s targeted growth rates. Calves are more likely to be limited by protein than by energy so protein levels should be greater than 16 per cent. Where cereal grains are fed, they should be limited to 2kg/day and supplemented with other protein-rich foods such as pasture silage. It is also important to ensure that calves are getting enough fibre such as hay and straw. This reduces the risk of acidosis, because the fibre is digested more slowly so there isn’t a rapid rise in acid production.
In hot weather, calves will often reduce their fibre intake because digesting roughage increases body temperature, but they will continue to eat all the grain offered — so special care needs to be taken with grain feeding at these times.
Obviously, prevention is far better than treatment, so what can you do to avoid grain overload?
Including buffers (sodium bicarb) in the grain mix will help to control the rumen pH; also, products such as Eskalin work by modifying the rumen microbes so that there are less of the bacteria that produce the lactic acid. Both these methods reduce the risk of acidosis but if the amount of grain consumed is excessive then acidosis can still occur.
The crushing of grain, while increasing the food conversion rate, also increases the risk of acidosis occurring so extra care should be taken if feeding crushed grain.
A lot of pellet mixes have rumen modifiers included, which can reduce the risk of acidosis.
The main priority is to control the calves’ intake of grain. Initially grain should be introduced to the diet gradually to allow the rumen time to adapt.
Self-feeders are great time savers but they must be used with care, as they are often the cause of accidental grain poisoning. It is vital that the feeder is adjusted correctly to deliver only the required amount of grain. Problems can arise where the feed is changed from whole grain to crushed grain, for example. If the settings are not altered, the crushed grain can flow more freely so giving calves access to greater amounts.
When feeders are introduced for the first time or when a new grain mix is used, we recommend that only one-and-a-half days’ ration is used initially. That way, if there is a problem with the setting, the calves will only get 50 per cent extra which shouldn’t cause too much trouble.
If you have any grain bunkers or stores on the property, ensure that they are securely fenced off and gates are kept closed to avoid stock access.