By Dr Jolly Kabirizi
During the rainy season like now, plenty of lush, green pastures are available for livestock.
However, these lush pastures are often very high in moisture; therefore, diluting their nutrients. The result is that animals have a difficult time consuming enough to meet all of their nutrient requirements. One of the problems commonly seen during the early grazing season is pasture bloat.
Bloat is a digestive disorder characterised by an accumulation of gas in the first two compartments of a ruminant’s (cattle, sheep, and goats) stomach. Gas is a natural by-product of ruminants’ digestion, and is usually relieved by eructation (belching).
Pasture, or ‘frothy’, bloat, results from the production of a stable foam that impairs the animal’s ability to relieve these gasses, thus causing the rumen to expand and compress the lungs.
Once this happens, the oxygen supply will be cut off and the animal will suffocate, sometimes in as little as an hour.
Bloat can be caused by grazing animals on lush pastures – typically pastures or small grains – that are low in fiber and highly digestible, but bloat is most commonly seen in animals grazing on immature legume pastures, specifically clover and alfalfa.
Other legumes, such as arrowleaf clover, berseem clover, sericea lespedeza, annual lespedeza, and crown vetch, contain leaf tannins that help to break up foam. However, some animals, such as ‘aggressive-feeders’, are more susceptible to bloat than others.
Clinical signs of bloat include; rapid swelling on the left side and signs of discomfort, such as kicking at their bellies.
Catching bloat in its early stages often yields the best results. Bloat can occur in as little as 15 minutes to an hour; however, there is usually a 24 to 48-hour lag before bloating occurs.
Immediately remove a bloating animal from the bloat-inducing pasture and offer them dry hay. This will reduce the bloat problem in all animals that will eat. Forcing bloated animals to walk can increase belching.
Remember to handle bloated animals gently since their breathing is impaired. If this does not lessen the bloating, then you can try to manually release the gas by:
1) Stomach tubing – this involves restraining the animal and passing a rubber hose down the esophagus.
2) Trocar – this is a device that punctures the rumen from the outside and is a rapid and effective means of releasing the gas.
This should be used as a last resort as animals treated with a Trocar will require antibiotics to prevent peritonitis (a potentially deadly inflammation of the abdominal lining).
Just like with grass tetany, prevention is the best treatment for bloat. If your pasture is predominantly legumes, like clover, consider over-seeding your pasture with pasture grass.
Bloat has very rarely occurred in pastures that are a 50/50 mixture of grasses and legumes. Do not turn out hungry animals on lush legumes or small grains pastures without feeding them hay or supplemental grain.
Finally, invest in anti-bloat products with poloxalene in them. Poloxalene is an anti-foaming agent that prevents bloat for 12 hours by breaking down stable foam.
A good, easy-to-use source of poloxalene is a salt molasses block – there are 30 grams of poloxalene per pound of block. To use, remove other sources of salt, and replace with poloxalene blocks – about 14 kgs per 4-5 animals (cattle) – at least three days before placing animals in pastures with significant bloat risk.
