The fiber digestibility of Italian ryegrass is high enough to replace a third of the alfalfa and corn silage in dairy diets, says Dave Combs, a University of Wisconsin dairy scientist.

“We’ve known for a long time that ryegrasses in general are very different from most other grasses,” Combs says. “In New Zealand and other areas with cool weather and adequate rainfall, perennial ryegrasses seem to be the core of their pasture systems because they’re so highly digestible. Italian ryegrass is an offshoot of that and has really been managed for high fiber digestibility or high nutrient value.”

He saw that while testing a new way of estimating forage value, called total-tract NDF digestibility (TTNDFD).

Analyses of Italian ryegrass and comparable grasses were studied from samples submitted to Rock River Labs, based in Watertown, WI. “In virtually every case, the fiber digestibility values that we get with TTNDFD tests are considerably higher with the Italian ryegrasses than other grasses of similar fiber content,” he says.

Combs conducted feeding trials replacing a third of the traditional forage in a dairy ration with a Barenbrug Italian ryegrass called Green Spirit.

“In a nutshell, we found that we could take alfalfa and corn silage out of dairy diets and replace it with higher-fiber Italian ryegrass. We got equal intakes and higher milk production.” Fat tests were up, too.

Essentially, 9-11 lbs/cow/day of grass dry matter were fed.

“It’s a lot of grass. When I first did these trials, one thing I used to do was take the TMRs out to farmers to show them. Most people who are seasoned feeders, when they see that much grass in a ration, they get a little nervous.

“We were also interested in cow health on this study” – particularly lameness, he says. But the limited trial and lack of overcrowding weren’t conducive to studying the problem. “If we could see this in a more typical commercial setting where cows are spending more time standing, I think higher-fiber diets might actually help lameness. But that’s conjecture at this point.”

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