Articles on forages, animals, and grazing systems
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Extension Forage Specialist
University of Kentucky
Phone: (859) 257-3358
Fax: (859) 323-1952
In Kentucky, bloat is most common from mid-March through May but many cases of bloat have already been reported this spring. Legumes are the main cause of bloat but lush cereal grains such as wheat, oats, barley, and rye can also be a source. Utilizing legumes has many benefits such as providing forages with nitrogen by fixing nitrogen in the soil and also improves pasture quality which can result in increased animal performance. Small grains can provide high quality grazing, silage, or hay and can extend the fall and spring grazing season. Although these forages have many benefits, bloat can decrease animal performance and can cause death.
White or ladino clover and alfalfa are the main species associated with bloat in ruminants. Frothy bloat, which can cause death in one hour after grazing begins, is caused by the formation of foam in the rumen. This foam does not allow for the fermentation gasses with are usually belched out to escape. As the gas accumulates, pressure increases and the rumen stretches. This affects the animals breathing and makes it difficult for the animal to inhale which can lead to suffocation. Legumes and cereal grains that are high in soluble protein and low in lignin can cause a slime, which reduces the ability for fermentation gas and rumen contents from being expelled, to form. Gaseous bloat, which does not involve foam and only accumulation of gas, is not associated with grazing but with feeding grain.
Knowing and watching for symptoms of bloat is vital in order to manage this disorder. Bloat may occur in as little as one hour after animals are turned out on pasture but is more common after two or three days. When bloat occurs, the left region of the abdomen visibly swells. Repetitive standing up and lying down, kicking at the belly, frequent defecation and urination, grunting, extension of neck and head, lethargic animals, and difficulty breathing are also common bloat symptoms. As bloat becomes more severe, rumen contractions will cease and if tapped, rumen will make a drumlike sound. In severe cases, death usually occurs 3 to 4 hours after symptoms begin.
Although risk of bloat cannot be eliminated, if managed correctly, livestock can graze stands with a significant proportion of legumes or small grains with little risk of bloat. Having grasses and legumes mixed in pastures rather than grazing pure legume stands will greatly decrease the risk of bloat. Certain legume species have lower or no risk of causing bloat. When moisture is high, from rain or dew, there is a higher risk of bloat. Animals should not be turned out onto pastures with a high proportion of legumes until midday when morning dew has dried. Also, do not graze very immature white clover or alfalfa. Turning out hungry animals onto possibly hazardous pastures will increase bloat potential. Feeding hay before turning out can also be a useful management tool. Livestock should always have access to water and minerals and should be watched closely for signs of bloat, especially after a change in weather.
Feed additives can effectively reduce the risk of bloat. Antifoaming surfactants and antibiotics are often used to reduce bloat occurrence. Poloxalene is a surfactant that lowers the surface tension of the foam and collapses it back into liquid form. This additive comes in block form,a granular form which can be mixed into supplemented feed, and in liquid form which is used as a drench to quickly treat bloat. Ionophores are an antibiotic that work by preventing the growth of certain microbial species in the rumen. Research has shown that the use of poloxalene is more effective.
Treatments for animals experiencing bloat involve methods to allow fermentation gas to escape. Passing a stomach tube with a large diameter can release pressure in gaseous bloat conditions. If animal is experiencing frothy bloat, this technique will not be effective but an antifoaming agent can be given when tube is in place. Various vegetable oils, mineral oil, and a poloxalene drench concentrate can be used to break up the foam and allow for gas to escape. Contact your veterinarian for more information on dosages and treatments. In emergency situations, puncturing the rumen with a trocar and cannula can be used to relieve pressure. A trocar fits inside the cannula and is inserted into the abdominal wall in the middle of the animals left flank. The trocar is removed and gas and foam are allowed to escape. An antifoaming agent can also be poured into the rumen through the cannula. An emergency rumenotomy, where a large hole is cut into the rumen, can be performed in life-threatening conditions.
There have already been significant reports of bloat this year. Properly managing forages and grazing to reduce risk. Using feed additives can be effective to protect livestock. Observe animals grazing on pastures with high legume concentrations and treat animals when necessary. Having legumes and/or small grains in pasture-based systems can be extremely beneficial to pasture quality and animal performance. Although there is a possibility of decreasing performance or losing animals to bloat, if managed properly, the risk of bloat can be greatly reduced. For more information on bloat prevention see “Managing Legume Induced Bloat in Cattle”.
The risk of bloat can be greatly reduced if managed properly.