Forage options for the pregnant heifer

MARSHFIELD, Wis. — Forage-based diets containing large amounts of corn silage or other high-quality forages often exceed the energy needs of growing dairy heifers. When consuming such diets, heifers usually eat more than they need, leading to undesirable weight gain and over-conditioning.

Research has shown that increasing fiber in the pregnant heifer diet reduces unnecessary intake. Diets focused on fiber typically reduce feed intake in pregnant heifers by 10%.

Matt Akins is a dairy scientist and research leader in the Environmentally Integrated Dairy Management Unit with the U.S. Department of Agriculture-Agricultural Research Service’s U.S. Dairy Forage Research Center.

“We don’t want excessive condition going into lactation,” Akins said “An ideal body condition score for heifers is 3.25-3.5. We don’t want heifers coming in at 4-plus. Having more body fat can cause hard calvings and problems into early lactation.”

Akins and his colleagues have conducted studies using higher fiber forages in the diets of animals that have been bred or confirmed pregnant. Over the last several years, their studies have focused on forages capable of increasing fiber and diluting energy in rations.

“Feeding a higher fiber diet with lower energy was the goal, and we found that heifers fed this diet have more optimal weight gain,” Akins said. “They eat less and gain a more appropriate weight, compared to feeding a higher energy diet based on corn silage and alfalfa.”

Akins’ work is based on the fact that dairy heifers generally eat about 1% of their body weight in fiber each day.

“The rumen can only fit so much fiber in it,” Akins said. “We can use that to our advantage by feeding higher fiber diets to control feed intake.”

Nutrition targets for the pregnant heifer diet are 50%-55% neutral detergent fiber, 55%-60% total digestible nutrients and 13%-14% crude protein.

“That puts us pretty close to where we need to be for energy,” Akins said.

When feeding a high-fiber diet, Akins has found that feed intake is often reduced by 5%-15%, depending on forage type and fiber levels, with a 10% decrease being typical.

Akins said a gain of 1.8-2.2 pounds per day is ideal growth for a Holstein heifer, and heifers on these higher fiber forage diets are reaching this level of growth. On the other hand, heifers consuming diets of corn silage and alfalfa containing 45% NDF and 65% TDN were gaining 2.5-3 pounds per day in Akins’ studies.

“If we go above 2.2 pounds, heifers start to get overweight and have too much condition,” he said. “They put less growth into muscle and more into fat, especially as they get closer to maturity.”

Akins said this is particularly problematic in confinement situations where heifers get less exercise. In ultrasounds on pregnant heifers consuming a high-fiber forage diet, researchers saw less fat growth on heifers’ backs and less internal body fat, particularly on the kidneys.

Furthermore, frame development on heifers is as good or better on these diets as it is on a higher starch corn silage diet.

Through their testing of various forage options, Akins and other researchers have discovered that any higher fiber forage can accomplish these weight goals.

He said sorghum-sudangrass works fairly well as do other types of straw. Wheat straw, corn stover, and Eastern gamagrass are some of the forages Akins and colleagues have conducted studies on at the University of Wisconsin-Marshfield Agricultural Research Station.

“Any of these three works well, especially gamagrass in a chopped corn silage,” Akins said. “Corn stover tends to have problems with sorting if it’s not chopped down fine enough. It’s necessary to process wheat straw and corn stover more aggressively to ensure heifers eat it.”

A distant relative of corn, Eastern gamagrass is a perennial warm-season grass that can survive winter conditions. It thrives on a one-cut harvest system, with yields maximized during mid-to-late September and concentrations of neutral detergent fiber ranging from 75%-80%. During feeding trials, heifers did not exhibit sorting behaviors with Eastern gamagrass.

Akins plans to do additional testing on other forages in the next few years.

“There are a lot of options people are working with,” he said. “It depends on the agronomic system on your farm and soil conditions.”

Akins said one example that can potentially work well in heifer or dry cow rations is long-day corn silage. It never fully develops an ear and therefore yields a lot of forage tonnage without grain.

Akins and his team continue to investigate new types of forages and plan to do feeding trials with long-day corn silage in a couple of years. They are also looking at pearl millet as a future option.

“Depending on how you manage it, pearl millet would be a fairly good candidate for this type of diet,” Akins said. “We did some test plots on it last summer and are going to do more in the upcoming year.”

Large-scale field studies and feeding studies on pearl millet are in the works for 2026. He said they first need to tweak agronomically how to plant the crop and get a better stand.

From 2021-2022, Akins was part of a study done on the perennial intermediate wheatgrass crop, Kernza. After harvesting the grain, the stem and leaf material is harvested like wheat straw. During a feeding trial, the team found that Kernza worked well in a heifer diet and could be a good replacement for wheat straw.

Lower feed costs is another benefit of a fiber-based diet. Most high-fiber forages cost less to produce than corn silage or haylage. Akins said farmers can also purchase these forages on the market fairly economically.

“Sorghum-sudangrass bears a pretty significant cost reduction at a savings of 20-25 cents per animal per day,” he said. “A single-cut system is ideal for getting the highest fiber value.”

A single harvest for these high-fiber forages at bloom stage produces 1.5-2 times more biomass than a 2-cut system, Akins said.

Dan Olson, owner of Forage Innovations, said crops that can be grown in between other grain crops lower the cost per pound of dry matter and help spread out land cost.

“Finding crops that fit in between years of corn, such as sorghum-sudan, can really help,” Olson said.

At Forage Innovations, Olson and his team unite agronomy and nutrition to optimize forage systems. Olson works with about 300 dairy farms in 27 states and also milks cows on his farm in northeast Wisconsin.

Olson said pregnant heifers do well on a single-cut product like sorghum-sudan or a forage sorghum.

“When you combine a warm season annual like sorghum-sudan with a winter small grain like triticale or cereal rye to maximize the cool portion of the year, you can regularly get 10 tons of dry matter in the Upper Midwest,” Olson said.

One of Olson’s clients in South Dakota is producing cereal rye and sorghum-sudan with out-of-pile costs at 4.5 cents per pound of dry matter.

“That’s 3 cents a pound less than wheat straw, and it’s a better product,” Olson said. “He has the ability to save 70-80 cents a head per day on ration costs.”

This strategy also helps promote soil health while providing more crops per acre.

“My favorite crop is a (brown midrib) photoperiod sensitive sorghum-sudan,” Olson said. “It has a lot of fiber and stays vegetative and growing until mid-September. It’s cheap to grow, which helps lower feed costs.”

Dairy farms have options when it comes to supplementing high-fiber forages into pregnant heifer diets. Akins said working these forages into the ration should be done in tandem with advice from a nutritionist.

“Work with your nutritionist in getting feed tested properly for nutrient values and in balancing diets properly for fiber, energy, protein, minerals and vitamins,” Akins said. “That’s critical.”