Why bloat is common during rainy seasons

Dear Daktari, I am a dairy farmer and I recently encountered a case that nearly claimed my precious dairy cow. I was lucky because I called in a veterinary doctor who quickly saved my cow but warned me that bloat is a fatal condition. My problem he said was the lucerne I was feeding my cow on. With the rains, I had planted a large area and I had seen an increase in milk yields after I fed the lucerne to the cow and hence the temptation to give more. I am sharing this information with other farmers who may fall into such problems. [Charles Wanami, Bungoma County]

Thank you Mr Wanami for reaching out to us. Bloat is common in succulent pastures. Legumes that include lucerne, alfalfa and clover top the list of succulent pastures that can easily cause bloat. Others include young green cereal crops and sukuma wiki that are now in great supply thanks to the rains. Grains can also cause this type of bloat. Legumes have a natural substance called - saponin which forms in the stomach and traps gas forming small air bubbles that hold onto air that ought to be released or eructated over time. This causes pressure to build up in the rumen; impairing other physiological functions for example breathing. They cause primary bloat; and this is the commonest type of bloat. These culprit feeds also lower the production of saliva that has anti-foaming abilities and help in eructation (release of air or gas from the stomach or esophagus through the mouth) and digestion.

The microorganisms in the ruminant's rumen generate lots of gases as they digest the cellulose in the feeds and most of this gas is belched or eructated out. If this does not happen it quickly accumulates and causes distention of the stomach. Bloat is a fatal condition that if not addressed in good time, can result in death within a very short time. Secondary bloat on the other hand arises from gas that is separated from the feeds in the rumen but cannot be expelled. Secondary bloat is due to an obstruction of eructation caused by foreign bodies like potatoes, avocados, diseases that present with space-occupying lesions that can obstruct the esophagus.

Clinical signs of bloat

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In acute cases, the animal will be found dead. This can happen as early as one hour after the onset of bloat. A swollen rumen is the commonest clinical sign - the left flank will be visibly swollen. Difficulty in breathing, grunting, mouth breathing, protrusion of the tongue, head extension, increase in rate of urination are among the clinical signs of bloat.

Treatment and prevention of bloat

Antifoaming agents are used to treat primary bloat. Secondary bloat is relieved through the removal of obstructions or puncturing the left flank with a trocar and cannula. Note a veterinary doctor should do these. Antifoaming agents include vegetable oils and mineral oils (paraffin). Bloat can be prevented by good animal husbandry practices that include using hay mixed with lush pastures. Mature pastures are less likely to cause bloat as compared to young pastures. Antifoaming agents can be added to the animals' feed or water or incorporated into feed blocks.

[The writer is a veterinary surgeon and the head of communications at the Food and Agriculture Organisation of the United Nations (FAO) Kenya. The views expressed here are not necessarily those of FAO]