Pasture bloat cause for concern this spring

You survived another long, drawn out winter. As your hay pile quickly dwindles, you are eagerly awaiting the day you can turn cattle out to pasture even more than your cows are.

The only problem is that grass growth is stunted. Dry conditions and cooler-than-normal temperatures are setting back pasture growth this spring.

Grazing alternative forages may be an option to buy you a little more time before turning cows out to grass pastures.

“Because it had been dry last year, with a shortage of hay this spring and winter, a number of people are grazing wheat pasture or rye pastures,” reported Jerry Volesky, range and forage specialist based out of the West Central Research and Extension Center in North Platte, Nebraska.

Grazing high-risk forages must be done with care to prevent bloating. Pasture bloat is usually associated with grazing wheat, rye, alfalfa or other legumes, such as white clover or red clover.

“These forages digest quickly in the rumen, and that releases a lot of gases that have a tendency to get trapped and ultimately cause bloat,” Volesky said.

Bloating is a serious cause for concern. In the last stages of severe bloat, a few seconds delay in administering treatment may be the difference between life and death, according to NebGuide G2018 “Bloat Prevention and Treatment in Cattle.”

Springtime presents the ideal conditions for pasture bloat. With cool, damp days or mornings with a heavy dew or light rain, the incidence of bloat can be a little higher, said Volesky. Although it has been dry, bloat is “always something to look out for when grazing different types of forages.”

Grazing a pasture of alfalfa or other high-risk forage interseeded with grass or another non-bloating legume, including birdsfoot trefoil or cicer milkvetch, can lower the risk of bloat while meeting cattle’s energy and protein requirements. The stand should be at least 50% or more grass to lower the chances of bloat.

More Information

Minimizing bloat while grazing alfalfa-based pastures can be divided into three overarching management strategies:

Pasture Establishment

• Plant mixtures of alfalfa with grass or non-bloating legumes so that alfalfa provides no more than 50% of the available forage. Observe plant growth rates and alfalfa-grass proportions throughout the growing season. (See section on “Alfalfa and Grass Mixtures,” NebGuide G2030.)

• When they become available, plant “bloat-reduced” (low initial rate of digestion) alfalfa varieties that are adapted to Nebraska growing conditions. Note: Current grazing-tolerant varieties are not bloat-reduced.

Livestock Diet Supplements

• Provide a bloat preventative (poloxalene) to livestock several days prior to and while grazing alfalfa.

• Provide bloat-reducing compounds such as Laureth-23, antibiotics (oxytetracycline, penicillin) or ionophores.

• Provide mineral supplement with adequate sodium (salt) and avoid excessive potassium, calcium and magnesium.

• Allow livestock free-choice access to grass hay while grazing lush alfalfa or windrow portions of pasture several days prior to grazing.

Grazing Management

• Never turn hungry livestock into an alfalfa pasture.

• Made paddock rotations midday or later.

• Wait until moisture from dew, rain or irrigation water has dried before turning livestock onto fresh alfalfa.

• Avoid dramatic changes in forage quality when rotating from paddock to paddock by leaving adequate residue.

• Observe livestock closely the first few days and remove any “chronic bloating” animals.

• Avoid grazing alfalfa before the 10% bloom stage. This may not be possible when spring grazing or grazing season-long. Closer observations for bloat should be made when many plants are at a younger growth stage.

• Be extra observant for bloat when a rapid flush of alfalfa growth occurs, such as during cloudy wet periods in the spring and after plant stress, such as hail or drought.

• Delay grazing alfalfa for 3 to 5 days after freeze damage.

From UNL NebGuide G2030 “Grazing Alfalfa” by Jerry Volesky and Bruce Anderson

Volesky said it is a little late to interseed now, but he offers tips for producers seriously in need of something to graze before their main grass pastures are ready.

First, if grazing an alfalfa field, let the plants become more mature before grazing. Alfalfa that is 6-8 inches tall is more likely to cause bloat than when the alfalfa is starting to flower later in May.

“The more immature the plant, the greater risk for bloat,” Volesky said.

Alfalfa grown at lower than normal temperatures or that has suffered frost damage is also more likely to cause bloat, according to NebGuide G2030 “Grazing Alfalfa.” Closely monitor the herd under these conditions.

Furthermore, do not turn hungry animals out onto a pasture of high-risk forage. Fill them up first so they do not gorge on fresh, lush forages that could cause bloating.

Rotational grazing can also help minimize problems with bloating, if done correctly. About 4-6 inches of stubble should remain when the herd is rotated. This is not only to ensure regrowth of the vegetation but also because forage quality and intake decreases the longer animals graze an area. As stated in NebGuide G2030, “grazing that leaves very short stubble could lead to a greater risk of bloat if livestock are hungry when turned into the next paddock.”

The first several days in a field are important when grazing high-risk forages. “After being there a week or so, the animals seem to adapt,” Volesky said.

Certain animals may also have grazing patterns conducive to bloat. Volesky referred to “chronic bloaters,” who may need different grazing management.

“An animal may specifically select for the nice, tender alfalfa plant and, as a result, may begin to bloat,” Volesky said. If possible, remove the animal with a tendency to bloat from the pasture.

Culling a chronic bloater from the herd may not be necessary, though. Volesky shared studies in New Zealand comparing herds of cattle that were divided into groups of low-susceptibility for bloat and high-susceptibility for bloat. Cattle in the low-susceptibility group had one similar gene, but that did not make a notable difference.

“Given the right conditions, they will still bloat,” Volesky said.

Providing a mineral or block containing poloxalene, an anti-foaming substance, can help reduce the incidence of bloat. Give animals access a few days before and during grazing high-risk forages.

Another option for the future is to seed bloat-resistant varieties of alfalfa. Canada has been conducting research to develop varieties of alfalfa with less bloat potential, said Volesky.

“They are not so rapidly digested in the rumen,” he said. These bloat-resistant varieties may be less cause for concern for bloat, but a chance exists nonetheless.

Grazing alfalfa or other alternative forages can give producers a few more weeks of growth before turning cattle onto grass pastures. If little grass is available, it may be the difference between surviving the summer or culling your herd.