Barley poisoning in cattle does not occur often, but cases can quickly become fatal without quick diagnosis and treatment. Hannah Park speaks to vet Ian Roper to find out more.
Cattle typically begin to show signs of ruminal acidosis, commonly known as barley poisoning, 12 to 24 hours after overeating barley, but anything starchy can trigger a reaction.
Those affected experience symptoms including diarrhoea and dehydration, but the first visible sign is often animals being unsteady on their feet. They can appear as if they are drunk, says Ian Roper, of Westpoint Vets.
He says: “As a result of a change in the population of bacteria in the rumen, more lactic acid is produced and causes a drop in pH levels, affecting the brain and causing animals to become unsteady on their feet. A normal bovine rumen pH level of 6.5 can be reduced to 4.5 in some cases.
“The extra lactic acid can convert to sodium lactate, drawing fluid into the gut which cannot reabsorb quickly enough and is why animals suffer from diarrhoea and dehydration.”
This change in bacterial population in the rumen fuels the production of more lactic acid than normal bacteria.
Mr Roper says: “The increased acidity irritates the lining of the rumen. This means bacteria usually contained in the rumen are also able to escape and can find their way into the bloodstream and end up in the liver. Blood vessels become narrower here so bacteria can easily become lodged.
“Stationary bacteria here with a good supply of nutrients and oxygen will multiply and form abscesses which can compromise liver function if left untreated.”
Mr Roper explains the reaction can occur in cattle of any age or system, but cases are more often seen in groups of beef animals on a cereal-based finishing system due to the nature of their diet.
“Cattle can cope with a cereal-based diet if it is properly managed. It needs to be introduced into the diet over a period of time, gradually increasing the amount of grain which need to be constantly fed alongside some kind of fibre such as hay or straw,” he says.
“The rumen is able to tolerate grains up to a point, but the balance is easily disrupted if there is a brief period where roughage is not available.”
Another condition affecting mainly dairy cattle which may display some similar symptoms is sub-acute ruminal acidosis. It can also impact on rumen efficiency and animal productivity, but signs will typically be more subtle.
“Cases of barley poisoning in dairy cows are rare as the energy dense, starchy products are usually fed to dairy herds as part of a total mixed ration so it is unlikely a large amount of starch would be eaten in one go.
“But if there is a slight imbalance and too much of these are fed in a ration, it will be counter-productive and cause similar symptoms to ruminal acidosis, but more slowly with more subtle symptoms.
“Acidosis also occurs when animals escape from housing into feed stores. These can be the most serious cases but often treatment is started promptly as farmers know animals will be affected.”
Early diagnosis is key to treating animals with this problem, with the priority to reverse the pH levels and excess acidity in the rumen to prevent long-term problems.
Mr Roper says if animals are suspected to have eaten a large quantity of starchy feed, it is important not to wait for them to get ill.
“It will be more effective if pro-active treatment is taken as soon as possible.
“Bicarbonate of soda and magnesium oxide can be given to buffer the acid, which is tubed directly into the stomach. I would also include an anti-inflammatory plus a broad-spectrum antibiotic to try and kill any bacteria in the bloodstream before a liver abscess has time to grow.”
He says it is also worth topping animals up with vitamins B1 and B12. Both are normally manufactured by ruminal microbes required for metabolism.
“Acidosis will also kill off the bacteria responsible for producing these vitamins at a point where animals critically need them so it is also worth administering these to top levels up,” he says.
“Surgical intervention can also be used to treat animals, but this is only effective if the animal still has starch in the rumen which can be physically removed, and is a fairly high risk procedure.”