A dairy heifer diet of wet distillers' grains and cornstalks, straw or low-quality hay could stretch forage supplies this winter, suggests Alvaro Garcia, South Dakota State University dairy scientist.

It's also a relatively inexpensive ration combination that provides “excellent” energy, protein and phosphorus, he says.

“We have been working a lot with wet distillers' grains in particular, because they are a really good match with underutilized fibrous resources like straw or cornstalks — even drought-stressed corn.”

Garcia and colleagues have tested the viability of both dry and wet distillers' grains — byproducts of ethanol production — in dairy rations. Wet distillers' grains (WDG) win hands down.

“When you put together dry forages and dry distillers' grains, they're too dry. The particles tend to separate and go to the bottom of the bunk so you don't get an even mix of feed.” Dry distillers' grains can also undergo a reaction in the drying process that makes proteins and sugars unavailable to animals, he adds.

WDG, on the other hand, are moist enough to blend rations and prevent sorting. “Protein, fat and phosphorus are really high in distillers' grains but are generally low in fibrous residues such as cornstalks and straws. So it's a perfect match to blend those feeds together and still get an acceptable feed.”

Garcia recommends that producers look at what forages are available on the farm that would blend with the nutrient-rich WDG. Protein in WDG is typically 30%; fat is 10-15%; and phosphorus, 0.75-0.9%.

They should then look at their heifers' growth stages, he says. “We have been suggesting that heifers should be started on this kind of feed when they are over 450-500 lbs. At that stage their rumen is fairly well-developed and can handle the fibrous residues.”

A 50-50 mix of fibrous residue with WDG, on a dry matter basis, works well, Garcia says. The idea is to produce a body weight gain of about 1.8-1.9 lbs/day depending in part on the height of the animal, Garcia says.

In a 50-50 blend of low-quality hay and WDG, for example, the hay provides about 10% crude protein while WDG provides 30%. “So you make a blend that has 20% crude protein, which is, for growing animals, acceptable.”

The fat factor, however, is one people take issue with, Garcia says. The energy source for most rations is starch, which is utilized mostly in the rumen. But distillers' grains have low levels of starch, because it has largely been removed for ethanol production. Although the fat in WDG is also a source of energy, it is absorbed in the small intestine. “So there are differences in the utilization of the energy,” Garcia says.

The proof that the WDG-residue combo works comes from farmers who have been using it, he points out. “Heifers have been grown all their lives on cornstalks and wet distillers' grains. There have been no problems with their future lactation performance.”

SDSU is now in the process of verifying that. The researchers are currently feeding heifers WDG and residues and will compare their first-lactation milk production with that of animals on a more traditional diet.

Producers, meanwhile, have been experimenting with ensiling WDG with cornstalks or other fibrous residues in bags.

“One of the concerns is that it preserves very well while you have it closed, but the moment you open the bag, the air infiltrates the mass towards the back of the bag,” Garcia explains. The large particle sizes of cornstalks leave air pockets within the bag, causing spoilage.

Producers need enough animals eating the ensiled blend so it doesn't spoil, he says.

“That's why some farmers have chosen to bag the wet distillers' grains and blend the day they are going to be feeding. And it works well.”