Brewers grains (also called brewers spent grain) are a good cattle feed: they run roughly 20 to 30 percent crude protein on a dry matter basis, supply digestible fiber, and cattle generally eat them well. The catches are that wet grains spoil in days and that they’re imbalanced in minerals, so they work best as part of a balanced ration rather than the whole diet.
What brewers grains are
After barley malt is mashed in hot water to pull out the sugars, what remains is the spent grain: husks, fiber, and protein. It comes wet (about 75 to 80 percent water, straight from the brewery) or dried.
Wet versus dried
- Wet: usually cheap or free near a brewery, but heavy to haul and perishable. In warm weather it can heat and mold in two to four days. Store it packed tight in a bunker, covered, or bagged, and feed it fresh.
- Dried: easier to ship and store, usually costs more per pound of protein, and is often pelleted or sold as part of commercial feeds.
How much to feed
Rations vary by animal and by the rest of the diet, but wet brewers grains are commonly limited to about 15 to 25 percent of total ration dry matter. Because the grains are mostly water, that is a lot of fresh weight, so do the math on a dry matter basis. Introduce them gradually over a week or two, and ask an extension nutritionist or your vet to help with the numbers for your cattle.
What to balance
- Calcium and phosphorus: brewers grains are high in phosphorus and low in calcium, so the ratio needs correcting, often with a calcium source such as limestone.
- Sulfur: can be elevated; too much in feed plus water can cause trouble in cattle.
- Roughage: don’t swap out hay or pasture entirely. Cattle still need long-stem fiber.
- Trace minerals and vitamins: keep a free-choice mineral available.
Handling tips
Check the grain each day for sour or moldy smells, clean feed bunks often, and don’t feed anything slimy or moldy. Make sure the supply is consistent, since a change in the brewery’s process changes the feed’s moisture and protein. If a brewery adds anything to the stream, ask what it is first.
If you are comparing byproduct feeds, see using beer waste for cow feed and beet pulp for cattle.
Bottom Line
Brewers grains are a low-cost protein and fiber source when fed fresh, in moderation, and with the minerals balanced. Test or ask for the feed’s nutrient analysis, and have your veterinarian or a nutritionist confirm the ration. This is general information, not a substitute for professional advice.
