You turn a bunch onto a stand of alfalfa or a clover-heavy meadow in the middle of June, everything looks fat and happy at dark, and by the time you get out there with the coffee one is stretched out on her side with a paunch blown up like a barrel. Frothy bloat doesn’t give you much warning. On the right feed under the right conditions it can drop a good cow in a couple of hours, and the ones that die are usually the aggressive eaters — the deep, productive cows you’d least like to lose.
It isn’t the gas itself that’s the problem so much as that the animal can’t get rid of it. Legumes like alfalfa, red clover, and white clover break down fast in the rumen and produce a stable foam. That foam traps the gas in thousands of small bubbles instead of one big pocket the cow can belch off. The rumen keeps swelling, presses on the lungs and the big vessels, and if nothing changes she suffocates or her heart quits.
When the pasture turns dangerous
The worst setups are the ones that look the best. A pure or heavy alfalfa stand, or a hayfield that got grazed instead of cut, is high risk — especially when the plants are young, vegetative, and growing hard. Add moisture and you stack the odds against yourself. Dew on the leaves in the morning, a rain the night before, or the flush of regrowth after an irrigation set all bump the risk up. Frost does it too, which is why fall grazing on alfalfa gets people killed the same way June does.
The dangerous window is the first several days after cattle go onto a new legume stand, before the rumen bugs adjust and before the animals settle into a steady grazing pattern. Hungry cattle turned out on an empty stomach will slug down a big load in a hurry, and that’s the load that ferments into foam. Cattle that have been on the feed a week and are grazing evenly through the day are at far less risk than the same cattle on day one.
How to keep the odds on your side
You don’t have to stay off legumes to keep from burying cows. You just have to take the edge off the situation so no animal eats a big fast meal on an empty gut.
- Fill them up first. Feed grass hay before turnout so they don’t hit the alfalfa starving. A gut that’s already got roughage in it fills slower and belches better.
- Turn out later in the day, after the dew burns off, not first thing in the morning onto wet growth.
- Don’t turn onto a fresh, ungrazed lush stand and then leave for the day. The first exposure is when you want to be around.
- Bring them along gradually. A little time on the stand each day for the first few days beats dumping them on full-time and hoping.
- Keep dry grass hay available in the pasture so cattle have something else to eat when the legume is at its rankest.
A poloxalene bloat block or bloat guard product, offered ahead of and during the risk period, is the tool most people lean on for pasture bloat. It works by breaking up the foam, but only if the cattle actually eat enough of it — check that they’re using it, because a block nobody licks does nothing. Diluting a pure alfalfa stand helps too; a field that’s part grass and part legume is a lot safer than a solid alfalfa piece.
Once regrowth matures and the plants start to bloom, the risk tapers off. Grazing management that keeps a good stand of grass mixed in, rather than letting alfalfa or clover take over a meadow, gives you a pasture you can use hard in June without holding your breath every morning.
When you find one down
A bloated cow stands with her left side ballooned out, drools, strains, and gets restless before she goes down. If you catch her on her feet, get her up and moving — walking helps some — and get her off the feed. A real emergency, a cow down and struggling to breathe, may need a vet or an experienced hand to relieve the pressure fast, and frothy bloat doesn’t respond to a simple needle stick the way gas bloat does because the foam won’t come out through a small hole. That’s a decision made in minutes, not an hour.
The honest truth is that prevention beats every treatment you’ve got. The half hour you spend watching a new bunch settle onto lush pasture, and the grass hay you feed before you open the gate, are cheaper than the cow you’d otherwise be dragging off with the loader.
