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OSU Extension

College of Food, Agricultural, and Environmental Sciences

May 11, 2021 - 8:00am --

Bloat in ruminant livestock ranges from mild cases of animal discomfort to a life-threatening situation. Bloat occurs when gases are trapped in the rumen of livestock. Normally, these gases produced by gut microbes escape from the rumen by traveling up the esophagus during the processes of cud chewing and belching.

In a recent Forage Focus video, Dr. Steve Boyles, OSU Beef Extension Specialist, and Christine Gelley, OSU Extension Educator in Noble County, discussed the causes, symptoms, and treatment of bloat. This video can be found on the OSU Beef Team Website:

Bloat is observed most often during the spring flush and in pastures with a high legume content (over 50%), especially forage species like clovers and alfalfa. The early flush of grass can also lead to bloat. This type of bloat is often called “frothy bloat” as the gases are trapped in many small bubbles mixed with rumen fluids and partially digested forage material.

Symptoms of bloat include a distended abdomen, diminished feed consumption, signs of discomfort, and in advanced cases an inability or reluctance to stand. As the gases build in pressure, the rumen expands and may cause a visible distension on the left side of the animal’s body. If bloat progresses, a distension of the right side may follow. Signs of discomfort may include standing still, a lowered head, excessive lying down, and a reluctance to move.

In severe cases, mortality occurs by suffocation as the animal is prevented from taking in air due to pressure exerted on the lungs by the rumen.

Livestock owners can reduce the incidence of bloat using several management approaches.

First, avoid making sudden changes to livestock diets. Rapid diet changes upset the balance of rumen microbes that aid in digestion and this contributes to the formation of frothy-bloat. In addition, livestock should be released onto pasture in the spring on a full or partially full stomach of the ration which they had been fed throughout the winter. This prevents overeating on lush pasture which is a major contributor to bloat. Diet changes should be made slowly over several days.

The other time overeating, which may lead to bloat, occurs is right before or after a severe storm. This is because animals may gorge in preparation for a storm and then afterwards if they have become very hungry waiting for the weather to improve. Feeding livestock in a sheltered area during severe weather can mitigate risks for bloat.

Avoiding applications of nitrogen fertilizer in early spring can also help to prevent excessively rapid forage growth which may contribute to bloat, not to mention grass tetany. Nitrogen applications are not often needed on mixed pastures containing at least 30% legumes, and if needed, split applications during late spring and summer would be preferred, even on a straight grass pasture.

If there is a risk of bloat developing in your livestock, feed blocks containing anti-foaming agents (preventing froth formation) can be made accessible to livestock. Mild cases of bloat may clear up with a little time but should be monitored closely to see if the condition improves of becomes worse.

If the condition worsens and the animal is obviously bloated, a large stomach tube, appropriate for the livestock size, can be administered to help relieve the gas. Ideally, the animal will be standing and restrained. If the stomach tube alone does not provide relief, an anti-foaming agent (commercial products, or 250-500 mL of mineral/vegetable oil) may be given through the tube.  Take care to use a feeding tube or hose that is not rough but is still sturdy enough to be fed down the esophagus. Also make sure that the tube enters the rumen and not the lungs. This can be checked by listening for obvious sounds of breathing versus a more gurgling sound accompanied by the smells of methane gas in the rumen.

There are other emergency techniques that can be performed to relieve some forms of bloat, but those will not be discussed in this article. Information on using a trocar to relieve gas in an emergency can be found online, or better yet by discussing it with your veterinarian. In all cases of severe bloat, contacting your local veterinarian is in the animal’s best interest.

Specific animals with chronic bloat may be genetically predisposed to this condition and may need to be culled. When multiple cases occur, reevaluate management practices that may contribute to bloat and adjust accordingly.

Matthew Nussbaum is an OSU Extension Agriculture and Natural Resources Program Assistant and may be reached at 330-264-8722.

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