Written by Paul and Melissa Beck
Make no mistake, it is a shocking sight to drive past a lush pasture and see cattle with swollen egg-shaped protrusions from their sides and dead swollen carcasses. To avoid this, producers simply need a little education, a plan and a supplement.
Frothy bloat is a preventable disease issue for cattle grazing high-quality pastures that can result in traumatic death losses and reduced performance. The rapid onset of pasture bloat and the short window from the occurrence of initial symptoms and death may be the scariest part of this disease.
Bloat can be an issue on small-grain pastures such as wheat – and legume pastures such as white and Persian clover or alfalfa – and can impact both calves and mature cows.
Death losses in bloat-provocative pastures have been reported to be as high as 15 to 20 percent of cattle on a pasture, which can be a massive economic loss for the producer.
Lost production from subclinical bloat may actually be greater than producers realize, but a lot of the costs associated with bloat are from lost production due to the producer’s fear of encountering bloat.
Cattle grazing on small-grain pasture can gain in excess of 2.5 to 3 pounds per day without added supplementation, so avoiding the use of legume or small-grain pastures based on a fear of bloat is unreasonable, especially when there are affordable and user-friendly methods for control.
Causes of bloat
Frothy bloat is caused by the formation of a stable foam in the rumen that disrupts the normal eructation (belching) patterns in the rumen. This foam traps gas in the upper area of the rumen, covering the esophageal orifice and not allowing gas to escape the rumen via eructation which, in turn, builds up in the rumen. Death occurs because of pressure buildup on the animal’s diaphragm and lungs and results in suffocation.
High-quality forages (clovers, alfalfa and wheat pasture) are commonly associated with this issue because they are very high in soluble cell contents (proteins and sugars) that are rapidly released in the rumen.
These compounds are broken down by ruminal microbes and form a stable protein matrix, which traps ruminal gases produced in the normal function of bacterial breakdown of forages, creating the stable foam.
Bloat is often associated with pastures in the late winter that have regrown in warming days in the waning winter. The pastures are very high in leaf content and nutritive quality.
When a cold snap occurs that freezes these plant tissues and ruptures plant cells, the soluble cell contents are even more rapidly available in the rumen of grazing cattle, exacerbating the bloat potential of the forages. Bloat can occur as soon as one hour after cattle have been placed on bloat-provocative pasture but often occurs within three hours.
Grazing management alternatives
There are several grazing management alternatives that can be used to decrease the incidence of bloat. Because this is a bigger issue for cattle that are able to consume large amounts of these high-quality forages in a short period of time, overstocking cattle on pastures to a point that forage intake is limited has been used in the past.
Alternatively, where rotational grazing is used, cattle can be placed on pastures after the forages have accumulated sufficient growth and maturity. This will increase the fiber content of the forages and, as a result, limit the bloat-provocative nature of the forages.
Offering hays or straws is often suggested as a management option to decrease bloat of cattle grazing high-quality pastures. Research conducted with calves grazing wheat pasture indicates that offering straw to supplement fiber in the diet and increase ruminal contractions has not offered benefits in reducing bloat, possibly because of the low intake of the supplemental straw.
Nutritional supplement options
Research conducted in Oklahoma and New Mexico indicates that the ionophore monensin decreases the incidence and severity of bloat for calves grazing wheat pasture. This option is attractive because ionophores increase average daily gains by 10 to 15 percent for a cost of about $0.03 per day above the cost of the carrier supplement, which is an economic benefit to stocker cattle producers.
Even though it decreases the incidence and severity of frothy bloat on pastures, it does not eliminate the issue altogether.
Providing monensin in a carrier supplement (such as corn or soybean hulls) is an attractive option for producers because it provides additional degradable organic matter relative to the degradable nitrogen present in the rumen of cattle grazing wheat forage, as well as improving gains and subsequently the economics of the supplementation program, and finally reducing the incidence and severity of bloat more effectively than other ionophores.
In New Mexico, it was found that feeding steam-flaked milo with 170 mg of monensin per day to calves grazing irrigated wheat pasture in early April decreased the incidence of frothy bloat by 40 percent (from 61 to 37 percent) due to increased ruminal pH, forage digestibility and fluid passage rate from the rumen.
Poloxalene is a surfactant and works to disrupt the froth which can form in the rumen causing bloat. Research shows that monensin works fairly well at preventing bloat, but poloxalene has been proven to be a more effective remedy for frothy bloat than monensin.
Providing poloxalene in a self-fed supplement (blocks or other supplements) costs $0.15 to $0.20 per calf per day depending on the cost of the supplement.
If poloxalene is fed only during the period that forages are most bloat-provocative, then the total cost of bloat control can be covered by the prevention of the loss of a single animal. As a management strategy, producers may consider using monensin until you have confirmed bloat issue, then switching to poloxalene once cattle show clinical signs of bloat.
Studies have been conducted since the late 1960s that indicate poloxalene at 1 to 2 g per 100 pounds of bodyweight per day dramatically reduces the incidence of bloat. If poloxalene is provided in the form of a mineral block, it is important to remove all other sources of salt and begin offering it several days before cattle are put on provocative pastures.
Cattle producers don’t have to live with the threat of bloat, and they don’t have to sacrifice quality forage systems in order to avoid it. There are options that make economic sense; producers have choices and simply need to find the plan that fits best with their production goals.
Paul Beck, Ph.D., is an animal science professor at the University of Arkansas Southwest Research and Extension Center. He specializes in grazing stocker calves, cow-calf production systems, forage management, forage quality and livestock nutrition. Email Paul Beck or call at (870) 777-9702.
Melissa Beck is a full-time stocker operator, a freelance writer and owner of Beck Media. She has a background in animal science and is a former extension educator.