Recent rains and warming temperatures has spawned a flush of growth on dormant and drought-stressed wheat pasture. With the new lush growth and increased intake often comes an increased risk of bloat.
Ruminants are able to consume so many different types of ingredients because the rumen serves as a large fermentation vat that houses microbes that break down feeds into nutrients. This is a very effective way to convert grass and grain to milk or meat. This fermentation process produces large amounts of gas, which could cause a digestive problem known as ruminal tympany, aka “bloat”.
Normally the rumen gas is expelled by eructation (belching). Any condition that interferes with that release will cause an over-distension of the rumen and reticulum. This condition is most common in cattle, but can occur in sheep and goats as well.
There are two main types of bloat and each one is caused by a different mechanism. The primary tympany is also known as frothy bloat. This frothy bloat is when the small bubbles of fermented gas is trapped in a stable foam, which cannot be eructated. This type of bloat most commonly occurs in two situations; the first being animals on pastures, especially pastures containing legumes such as clover or alfalfa. Legumes are rapidly digested in the rumen and this results in a high concentration of fine particles that tend to trap gas bubbles, but it is not only animal’s digestive system that contributes to this problem, it is also the attributes of the plants containing soluble proteins that act as foaming agents. Animals being exposed to new lush forage growth, or animals that are moved in and out of the pasture are more prone to bloating on pasture. The second situation that frequently causes a frothy bloat is animals in feedlot environment, especially when animals are being fed high levels of finely ground grains. Digestion of the grain increases due to the grinding which also produces a multitude of fine particles that can trap gas bubbles. In addition, there are some microbes that can produce an insoluble slime that aides in producing a stable foam when fed a high concentrate diet.
The secondary tympany or free gas bloat is caused when an animal cannot eructate (belch) the free gas built up in the rumen. This is largely due to an obstruction in the esophagus such as foreign bodies, abscesses or tumors. Another possibility might be the animal’s posture. Too often we find animals laying with their backs downhill, and in this position the animal cannot physically eructate.
The clinical signs of bloat are easy to identify on an animal, as there will be large protrusion of the rumen showing prominently on the animal’s left side. The animal will show signs of anxiety and rapid breathing possibly with their neck extended with their tongue out. Once an animal exhibits staggering and lays down, death will occur rapidly. If an animal is bloated, it can be treated by inserting a trocar and cannula through the side of the animal into the rumen cavity. If the cannula is inserted and provides some relief, an antifoaming agent such as vegetable oils or mineral oils should be administered through the cannula into the rumen. Another option could be to pass a stomach tube with a large bore down the animal’s esophagus. This is another great opportunity to administer an antifoaming agent. In either case watch the animal closely for the next couple of hours. For a frothy bloat, switching the animal to a higher roughage diet will be advisement. Reducing the incidence of bloat can be accomplished with pasture and feed management and/or through the use of Poloxalene, which can be fed as a topdressing on feed, in a grain mixture, in liquid supplements, or in molasses blocks. Because poloxalene is relatively expensive, some producers reduce the dosage or eliminate its use after livestock have been grazing pasture for several weeks or the conditions that favor the incidence of bloat decline. Another common management practices is to provide supplements or molasses blocks containing a bloat-reducing ionophore (example: Rumensin®).
Some animals are just more prone to bloat than others and some are even considered chronic bloaters. Management and a producer’s best efforts will not show much improvement in a chronic animal’s condition.
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