Feeding cover crops to milk cows

MADISON, Wis. — As the idea of feeding winter annual forages — also known as cover crops — to lactating dairy cows gains traction, many wonder what to feed and how much.   

Ken Kalscheur addressed these topics during his seminar, “Use of cover crops in dairy cattle nutrition,” Sept. 30 at World Dairy Expo in Madison.

Kalscheur, a research animal scientist at the U.S. Department of Agriculture’s Agricultural Research Service U.S. Dairy Forage Research Center, discussed how cover crops can be utilized in the diets of high-producing dairy cows.

Recent studies demonstrate that cover crop silages can be successfully included at 10% of the diet in early lactation and 15% of the diet in mid-lactation.

Kalscheur highlighted studies done in 2025 at Virginia Tech evaluating triticale silage at two maturities in high-forage or low-forage diets of lactating dairy cows. Triticale was planted in the fall and harvested in the spring at boot stage and soft-dough stage.

The high-forage diet contained 55% forage at a rate of 29.4% corn silage and 24.2% triticale silage for boot and soft-dough stage diets. The low-forage diet consisted of 36.8% forage, with 18.1% corn silage and 18.7% triticale silage in boot and soft-dough stage diets.

Other ingredients were formulated to have similar composition across the diets, which were low in protein at about 13%.

Since there is less roughage and it is easier to consume a high-concentrate diet, cows on low-forage diets almost always eat more, Kalscheur said, and that was true in this experiment. Cows ate about 61 pounds in the low-forage diet versus 58 pounds on the high-forage diet.

Cows on the low-forage diet gave more milk at 94-95 pounds per cow versus about 90 pounds per cow on the high-forage diet. Animals receiving forage harvested at boot stage produced about 2-3 more pounds of milk than those on the soft-dough diet.

“Generally, boot stage did better in the high-producing dairy cow diet, but cows actually performed better than expected on soft-dough stage, which is generally lower in quality,” Kalscheur said.

He said the key is determining when to harvest these forages. For milk cows, harvesting at boot stage for a lower fiber, high-digestible forage is typically desirable.

“We always want to try to get the highest quality forage, so boot stage is usually a much better fit,” Kalscheur said. “Fiber digestibility at this stage can be very high and provide optimal quality to support milk production.”

Waiting until a forage matures would result in a more fitting feed for dairy heifers.

“We actually want a lower quality forage for heifers in many cases, and in this case, we would harvest between heading and dough stage,” Kalscheur said. “This will provide higher-fiber, lower-energy forage which is ideal for pregnant heifers to avoid over conditioning.”

The U.S. DFRC conducted experiments on the inclusion of cover crops in high-production lactating dairy cow diets and early-lactation diets to determine effects of cover crop silage on intake, milk yield, milk composition, nutrient digestibility and methane production.

The high-production study included 65 cows at peak milk at 60-150 days in milk. Cows were fed one of five diets for eight weeks. The control was a traditional corn silage-alfalfa silage diet. Other diets featured a cover crop silage that replaced alfalfa silage and were included at 15% of the diet: rye-monoculture, triticale-monoculture, rye-hairy vetch-camelina 3-way mix, and triticale-vetch-camelina 3-way mix. 

Crude protein in the rye-monoculture cover crop silage measured 13%; triticale-monoculture was 11.5%; rye 3-way was 13.6%; and triticale 3-way came in at 11.1%.

“We were expecting that to be higher,” Kalscheur said. “Instead of getting it at boot stage, it was probably a little past boot stage because protein was lower. But if we look at fiber digestibility, these are all extremely high. They’re in the 70s, and that’s very typical when harvesting annual forages. That makes it easy to incorporate into diets, so it’s really a bonus when feeding these annual forages.”

The control diet contained 30% corn silage and 30% alfalfa silage. In other diets, 15% of alfalfa was swapped out in lieu of 15% cover crop silages.

“We wanted starch to be the same across the board and didn’t change high-moisture corn or corn silage,” Kalscheur said. “Crude protein was similar to the control at 16.8% and the cover crops at 16.2%-16.3%. Neutral detergent fiber was typical at about 30%, and starch was 24.6%.”

Half of the animals in this experiment were first-lactation heifers and half were multiparous cows, with intake averaging 53 pounds per cow per day for all diets.

Milk production was also similar in pounds per day, ranging from 84.6 for the rye-mono diet to 87.3 for triticale 3-way. Milk fat percent was also about the same at 4.2%, with the highest being triticale-mono at 4.23%. The control was 4.16%.

Protein produced small differences, with cover crops slightly higher than control — 3.12% for triticale mono and 3.02% for rye 3-way and control diets.

“Feed efficiency was about the same at 1.77, which means the replacement of 15% was very effective,” Kalscheur said.

In the early-lactation study, 80 Holstein cows were enrolled at week three to about 90 days in milk and fed one of five diets: a control diet of traditional corn silage-alfalfa silage, rye-monoculture, triticale-monoculture, rye-hairy vetch-camelina 3-way mix, and triticale-vetch-camelina 3-way mix.

The control diet contained 37.5% corn silage and 20% alfalfa silage. In cover crop diets, alfalfa silage was replaced by the cover crop, which was included at 10% of the diet, while corn silage content remained the same. Diets were balanced to about 17.5% protein.

“We fed a high-protein diet because there is more demand for protein in early lactation,” Kalscheur said.

Neutral detergent fiber was around 26%-27%. NDF digestibility was slightly greater for alternative forages at about 35% compared to 32% for the control. Starch was also balanced to be similar at around 27%.

Cows did well on annual forages with intake of about 60 pounds and no real difference noted across diets. Cows produced 110-120 pounds of milk per cow per day in the first 90 days of lactation. Cows on triticale 3-way gave the least at 104 pounds. Milk fat was similar. Protein was slightly different, ranging from 2.92% to 3.07%.

“In early lactation when we see feed efficiency numbers above 2, it generally means cows are at peak in terms of consuming enough feed to produce high levels of milk and try to maintain body weight,” Kalscheur said. “Feeding these annual forages is a means of maintaining intakes during early lactation.”

If a farm needs an emergency feed or additional forages, Kalscheur said these are the types of forages that can be easily incorporated into the diet without any detrimental effects. Furthermore, the conversion of feed to milk is basically identical.