Adding straw to dairy rations may help — or hurt — your herd's milk production. That's according to several dairy nutrition experts who have studied what's in straw and how it affects dairy cows.

“Straw is good news and bad news,” says Mike Hutjens, University of Illinois extension dairy nutritionist. The good news is that it's high in fiber, low in potassium and low in protein, something dry cows don't need much of. The bad news: It's high in fiber, low in other minerals and low in protein, which high-producing cows need.

Straw provides effective fiber to help keep the cow's rumen healthy and functional. It also dilutes the energy and starch in high-corn silage rations and protein in rations high in legumes.

Nutritionists and dairy managers have generally been feeding 1-2 lbs of straw to high-producing cows and up to 6-10 lbs, or 30% of a ration, to dry cows, Hutjens says.

“At dairy meetings I ask, ‘Who's feeding straw?’ and get four or five hands.

“I ask, ‘Bill, why are you feeding straw?’ He says, ‘I put a pound in and my cows came up 2 lbs of milk, ate less feed, the manure looks stiffer and milkfat, protein and rumen mat numbers increased slightly. That 1 lb of straw, costing about 7¢, gave back 2 lbs of milk, a 24¢ increase; a slight increase in butterfat, adding a dime; and less dry matter intake that saved me 6¢.’ All of a sudden, that 7¢ for straw looks like a 33¢ turnaround,” Hutjens comments.

“The next manager at the meeting may say he put in 2 lbs of straw and the cows went down in milk and couldn't eat as much feed. He did it wrong.”

Apparently, the entire ration was balanced on fiber and the straw reduced dry matter intake.

More than the quantity, growers should consider the quality of the straw they're adding, according to a study on the nutrient composition of wheat, barley and oat straws.

Pat Hoffman, an extension dairy scientist with the University of Wisconsin, and Tom Anderson, Shawano County extension ag agent, did the study.

“We simply didn't know what the nutrient compositions of straw were. We wanted to get a database of nutrient values of straw,” Hoffman says.

Basically, they found that all three types of straw varied greatly in composition.

“I was surprised by how widely the energy content of straws varied,” he says. “Some had TDN values of 25 and some had 55. And that's important to note because these straws are often used to cut the energy content of the diet.”

Mineral content also varied. “There's a lot of potassium in some of these straws,” he says, noting that it contributes to milk fever problems. “When we're feeding dry cows and have one straw with 2.86% potassium and another with 1%, that's quite a difference.”

Hoffman recommends that dairy managers probe and test straw used in rations. Wet-chemistry forage analysis is usually required, but producers can ask labs if NIR tests predict straw nutrient content. To download information on the study and testing, visit: www.uwex.edu/ces/crops/uwforage/StrawFOF.pdf.

“I think people feeding 4 or 5 or 6 lbs of this material in dry cow diets really should have it evaluated,” he adds. “If I'm feeding a pound of it to a lactating cow, I'm not worried because it's such a small percentage of the diet.”

How much straw is needed for a lactating vs. a dry cow?

“For high-producing cows, that number sits between ½ to 2 lbs,” Hutjens says. “The key is that you want to have enough straw to get the physical characteristics that you want, but not so much that you bulk up the cow and slow down how much she can eat.

“Some farmers are feeding dry cows 6-10 lbs of straw in the ration because it becomes more of a physical fill factor and keeps the rumen expanded and the cow cud-chewing. So, when she has a calf, we minimize displaced abomasum,” he says.

To provide effective fiber, however, straw particle size should be longer than ¾” and less than 2”. Or, as Wisconsin researchers suggest, half the width of a cow's muzzle. “If it gets much wider than that, the cow will sort it,” Hutjens agrees.

Dairy nutritionists have stressed for years the importance of feeding high-quality forages, especially to lactating dairy cows, says Maurice Eastridge, an Ohio State University dairy nutritionist. “And here we have a practice of feeding very poor-quality forage to these animals.”

Somewhat skeptical of the practice, Eastridge decided to test straw's performance against that of alfalfa and grass hays, with corn silage as the base.

“What we found out was, as long as we looked at these forages on an equivalent NDF basis, the performance of the animals was similar. Straw could be a source of effective fiber at a low inclusion rate.”

That, he says, should be 2-6% of a ration, chopped at an appropriate particle size. Straw that makes up less than 10% of a ration shouldn't have negative effects on animal performance, he adds, if the diet is well-balanced in carbohydrates.

Research that Eastridge reviewed showed that feeding 4-7.5 lbs/day of straw to dry cows can limit nutrient intake and digestibility and may affect performance of cows after calving. He advocates 1-3 lbs/cow/day.

David Byers doesn't believe straw is the best option to use to tone down a ration and provide good fiber.

“I think straw is a bit of a fad,” says Byers, a Galax, VA, veterinarian and dairy production consultant. He'd rather see dairy managers feeding alfalfa hay, wheat silage or byproducts such as whole cottonseed or cottonseed, peanut or almond hulls for lactating cows.

Eastridge agrees. Besides feeding additional alfalfa or grass silage, or hay, he also mentions cottonseed, which he investigated in the same study. Soybean hulls, wheat midds or brewers' or distillers' grains also provide fiber to help dilute starch in rations for lactating cows, but don't serve as effective fiber, he says.