You have heard of a farmer who woke up in the morning only to find one or several of his animals dead with their stomachs distended.
Bloat is a dangerous condition that affects cattle, goat and sheep when there is an abrupt nutritional change in the diet especially when they feed on lush green pasture following long rains. This means animals have too much gas in their stomach.
How it occurs
Ruminants such as cattle, sheep and goats have a four-chamber stomach with rumen, reticulum, omasum and abomasum compartments.
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The rumen is the largest compartment where the mixture of partly digested feed and liquid is continuously fermenting, producing large quantities of gas such as methane. A cow produces more than a thousand litres of gas daily.
Most of this gas is removed by belching or eructation during rumination/ “cudding”. If the gas cannot escape, the rumen distends and the animal gets bloat. It occurs when:
- Animals eat too much grain
- Animals consume too many legumes or too much fresh, lush grass
- The oesophagus is blocked so that food cannot pass in the stomach
Frothy Bloat
Occurs when the rumen becomes full of froth/foam. Animals get this type of bloat when they graze on wet, green pasture mixed with legumes in the field.
Foaming substances are found in plants like legumes; Lucerne and clover as well as cereal crops when they are young and green.
Frothy Bloat is due to the production of a stable foam, which traps the normal gases of fermentation in the rumen. Pressure increases because belching is inhibited.
The rumen distension initially stimulates rumen movements, making the frothiness worse. Later on because of the distension there is a loss of muscle tone and loss of the rumen's ability to move spontaneously, compounding the situation.
Saliva has antifoaming properties. Saliva production depends on the feeding rate. More saliva is produced when food is eaten slowly than when it is eaten quickly.
When animals rapidly feed on immature, lush, succulent, rapidly growing forages with a high concentration of soluble proteins they digest these quickly, thus less anti-foaming saliva is produced.
What causes frothy bloat?
- A change in the composition of certain pasture plants, the change enhancing the formation of a stable foam that hinders eructation/ ‘cudding’.
- At the start of wet season when the diet of grazing animals abruptly changes from dry feeds to wet lush pastures
- When animals feed on ripe fruits/ feeds that ferment easily.
- A sudden change in the type of feed.
- In feedlots with insufficient roughage, or feed ground too finely. This progresses to a deficit of rumen-stimulating roughage, hindering the spontaneous rumen movements, belching and release of gas.
- Some poisonous plants can cause bloat
Free Gas Bloat
In this type of bloat, the gas lies above the food in the rumen and is not mixed with it, as it is in frothy bloat.
It occurs due to physical obstruction of the oesophagus, often by a foreign body such as a maize cob, mango, potato, avocado, apple among others.
Grain overload leading to the stopping of the rumen wall contractions can also cause this type of bloat. Similarly, unusual posture, especially prolonged lying down, as may occur in a cow affected by milk fever.
Free gas bloat only affects one or two animals in the herd at the same time, not several as in the case of Frothy Bloat.
What are the main signs pointing to bloat?
- The left side of the abdomen behind the ribs becomes very distended. The right side also becomes distended later.
- The animal stops eating abruptly
- The animal may grunt and have difficulty in breathing
- Diarrhoea is common in cases of frothy bloat
- There may be mouth breathing
- The animal moves with the neck extended and front legs more apart
- Due to pain, the animal may stamp its feet on the ground
- Green froth comes out of the mouth and nose sometimes
- There may be an extension of the tongue from the mouth
- Animals may collapse and die after only an hour or so
- Adapted from Large Animal Medicine Texts and Merck Manual
Email; PKangethe@standardmedia.co.ke
