A Guide to Cattle Bloat: Symptoms, Causes & Treatment

Ruminal bloat is a condition in ruminants where the rumen and reticulum become excessively distended due to the buildup of fermentation gases, which can manifest either as persistent foam mixed with rumen contents or as free gas separated from the ingesta.

This condition occurs when the gas produced during fermentation cannot escape, and it is often a secondary problem in newborn calves. Within a few hours, ruminal bloat can become life-threatening, requiring immediate medical attention.

Causes of Ruminal Bloat In Cattle

The condition is caused by several factors, including oesophageal obstructions, consumption of lush or fertile sacculate pastures, carbohydrate overload, ruminal acidosis (which occurs when gases accumulate in the rumen), and ruminant atony (when the rumen stops moving).

Types of Bloat in Cattle

a). Primary Ruminal Tympany (Frothy Bloat)

This type of bloat occurs when gas bubbles get trapped in the rumen's ingesta, resulting in stable foam. Primary ruminal tympany bloat is caused by dietary factors and is commonly observed in cattle that graze on legume pasture or are fed high-grain diets in feedlots.

Abrupt changes in diet to lush pastures can also trigger this condition. Leguminous bloat is caused by the foaming qualities of soluble leaf proteins in legumes.

In primary ruminal tympany, coalescence of small gas bubbles is inhibited, leading to an increase in intra-ruminal pressure because eructation is prevented.

Frothiness can also occur when finely ground grain is added to the diet. This increase in grain content leads to a change in the number and proportion of protozoa and bacteria, which produces slime, resulting in stable foam. Salivation may also be inadequate, exacerbating the problem.

b). Secondary Ruminal Tympany (Free Gas Bloat)

This type of bloat occurs when free gas produced during fermentation in the rumen fails to escape through eructation. It is usually caused by physical interference with eructation, resulting in the obstruction of the esophagus.

Free gas bloat can also be caused by obstruction due to foreign bodies or tumors (known as choke), pressure from enlargements outside the esophagus, or obstruction of the cardia from the interior.

Interference with the nerve pathways responsible for the maintenance of the eructation reflex in anaphylaxis, actinobacillosis of the lower end of the esophagus, as well as atony due to vagus nerve damage, can also lead to this condition, especially in calves.

Clinical Signs of Bloat in Cattle

Animals frequently die suddenly, with bloat being a common cause. In primary pastures, bloat and distension of the rumen occur suddenly, about 15 minutes after grazing.

The distension is evident in the upper left flank, and affected animals display signs such as getting up and lying down, kicking at their belly, rolling over, and protruding their tongue. Salivation is also observed, and the animal may experience marked dyspnea, open-mouth breathing, and a tympanic tone on percussion.

In addition, the animal may exhibit labored breathing, frequent urination, and defecation. In a group setting, several animals may display mild signs, with some exhibiting a moderate condition that can be relieved by walking (eructation starts).

In secondary bloat, excess gas is present as a free gas cap on top of the solid and fluid ruminal contents. Dyspnea occurs in both types of bloat, marked by an increase in heart rate of about 100-120 beats per minute.

Treatment of Bloat in Cattle

To prevent bloat, drench each animal twice a day with an anti-bloat preparation or oil, and apply the preparation twice daily onto the flank. Additionally, add bloat oil to the water supply. To further prevent bloat, use a mixture of alcohol ethoxylate and molasses in a roller-licker drum or use anti-bloat blocks or dry loose licks.

If bloat does occur, the goal of treatment is to alleviate the pressure of gas before it causes heart failure. Administer animal bloat drench (500ml), and if unavailable, use linseed oil. The treatment works by dispersing the gas, but if the animal is unable to swallow the drench, it may indicate an obstruction that needs to be addressed.

Free gas can be expelled in a normal way, as seen below;

When an animal becomes bloated, it will typically belch within a few minutes. It's important to keep the animal standing, as lying down could result in sudden death.

You can even walk the animal for a short distance and use a broomstick to make it run up and down to release the gas. If the animal can't stand, you may need to relieve the gas using a trocar and cannula.

To do this, insert the trocar and cannula into the rumen on the left side, 5cm behind the last rib, and 15cm down from the spine. Once the gas has escaped, remove the trocar. However, be aware that this procedure can sometimes lead to peritonitis, so it's important to give the animal antibiotics to prevent infection.

If the animal can stand, you can also pass a stomach tube to relieve the gas. To do this, use a gag to keep the animal's mouth open and pass a 20mm plastic tube into its throat.

If you feel the animal swallow, push the tube slightly further into the esophagus. If the animal coughs and you feel air moving in and out of the tube, withdraw it and try again, as it may have entered the trachea instead.

This method tends to work best for younger cattle and may be less successful in adults, as the tube can become caught in food and fluid in the bottom of the rumen. In cases of frothy bloat, the foam is so stable that an anti-bloat drench may be needed instead.

It's worth noting that postmortem findings of bloat in cattle often reveal inflammation of the uterus and hemorrhages.

Prevention And Control of Bloat in Cattle

To potentially reduce the occurrence of bloat, consider grazing legumes for limited periods. It may be helpful to graze during the daytime and remove cattle to hay at night, or alternate between grazing legumes and grass pastures.

Various management practices can be used to lower the risk of bloat, such as feeding hay, especially orchard grass, before turning cattle out to pasture. Maintaining grass dominance in the sward or using strip grazing to limit intake can also help. It's recommended to move animals to a new strip in the afternoon rather than early morning.

When cows are grazing on lush pasture, it's advisable to provide them with hay or palatable straw. Additionally, ensure providing the right mixture of legumes and grasses in a 1:4 ratio, maintain good hygiene and management practices, and properly dispose of carcasses.

Conclusion

In conclusion, ruminal bloat disease in cattle is a serious condition that can have life-threatening consequences if not addressed promptly. It can be caused by various factors such as dietary changes, obstructions, and nerve damage.

Recognizing the clinical signs and understanding the different types of bloat are crucial in providing appropriate treatment. Prevention and control measures, such as managing grazing practices and providing proper nutrition, can help reduce the occurrence of bloat.

By staying vigilant, implementing preventive measures, and seeking veterinary assistance when necessary, farmers can safeguard the health and well-being of their cattle and ensure the productivity of their livestock operations.