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Deflate bloat with good forage management

The positive benefits that le­gumes provide to pastures and ani­mals include better protein content, higher mineral levels and greater energy than grasses alone—plus the fertility value of nitrogen fixation. However, a potential drawback of many pasture legumes is the chance of bloat.

Bloat is the result of rumen gas production exceeding the animal’s ability to eliminate the gas. Alfalfa and many clovers are all highly digestible. The protein in these legumes is readily accessible to the rumen microbes. When these microbes digest the forage, they re­lease gas. As the rumen swells with gas, it can eventually interfere with respiration. Depending on the diet, a large amount of foam or froth develops in the rumen and inhibits the release of gas, which causes the animal to bloat. Death from bloat is the result of suffocation.

Discontinuous grazing, such as the removal of animals from legume pastures overnight, is often associat­ed with bloat issues. Problems may also occur when grazing is inter­rupted by biting flies or adverse weather, such as storms. Anything that alters normal grazing habits will increase the incidence of bloat.

Environmental factors also contribute to bloat risk. That’s why animals may be fine for weeks and then experience a high degree of bloat overnight while grazing the same or similar pastures. Daytime temperatures around 70 degrees coupled with a cool overnight tem­perature will lead to a greater risk of bloating. High soil moisture, which results in high plant moisture, will also elevate the risk.

Alfalfa can cause bloat in the spring, summer and fall. Fall bloat conditions are caused by frequent heavy dew or fall frost. Following a killing frost, after enough time has passed, alfalfa has a reputation of being bloat-safe. However, if the plant stays green, or the leaves ap­pear glassy-shiny, the potential for bloat remains.

Pasture forages have different levels of bloat risk, as shown in the chart above.

To prevent bloat in pasture cattle, manage pasture for no more than 50% legumes. This becomes trickier if animals can selectively graze. Turn out cattle only after letting them eat dry hay or grass before grazing legume pastures. And don’t turn out cattle on wet pastures. Wait until the dew is burned off or the rain has dried.

The feed additive Bloat Guard (poloxalene) will prevent pasture bloat if consumed in adequate amounts. Begin to feed poloxalene for several days before turning cattle out on legume pastures. If using blocks, do not put them close to the water source, which tends to be less effective. Ionophores, such as Bovatec or Rumensin, will reduce the viscosity of the rumen fluid. This will reduce the incidence of bloat.

Frosted alfalfa will have an increased risk of bloat. When frost occurs to the initial spring growth of alfalfa, it’s best to wait at least several days to a week before mak­ing an evaluation of plant damage. Freeze damage and plant recovery are influenced by factors such as the actual overnight low temperature, soil temperature, field topography, possible snow cover, stand age, plant maturity and stand vigor. Frost damage will cause wilted leaves and stems.

If the freeze damage was slight— affecting less than a quarter of the upper stems—the wilt will dissi­pate in a couple of days. There is no need to do anything other than wait. Severe damage usually shows up later. If most of the top stems are damaged, and if the plants are less than 10 inches tall, the plants will recover without mowing. If the stand is taller than 12 inches in height, the damaged alfalfa should be harvested and allowed to re-grow.

Pasture bloat is a mostly prevent­able disease of grazing cattle. Fol­lowing these recommendations will help reduce chances your herd will experience the issue this spring.

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