One is to consider how wet the diet will be. “If you have wet distillers grains and you also have a fair amount of corn silage or other wet feeds, you start getting too wet a diet.” That causes gut-fill that may limit intake, he says.

Some producers tell Schingoethe that they can't add much distillers to rations because, when they do, their milk fat tests go down.

“The problem probably is that the distillers grains are at about 38-40% NDF. Dairy nutritionists and producers look at the analyses and say, ‘I've got plenty of NDF in the diet; I can cut back on the alfalfa hay.’ Then, all of a sudden, the fat test goes down.” The lack of effective fiber — not the addition of distillers — caused fat scores to lower, he says.

Although lower alfalfa yields and higher hay prices have forced producers to look at other fiber sources, make sure at least 50% of the lactating cow's diet is forage dry matter, warns Schingoethe. SDSU studies showed “a nice linear decrease in fat test” when forage dry matter went from 55% to 35-40%. Wisconsin research brought lower milk fat numbers on a 45% forage dry matter diet.

Before adding distillers to a ration, know what's in them. Newer ethanol plants, Schingoethe says, aren't always putting out a consistent product. So if a nutrient analysis isn't available, have one done, he says.

“Some ethanol plants are trying new technologies where they might start pulling off some of the fat to see if they can make biodiesel or something like that.”

That lowers the energy of the distillers grains and raises the protein content, which can be an advantage. “But if you're guaranteeing 30%protein and providing 33%, I, as a dairyman, could have saved some money by reformulating.”

Some plants, he says, are purposely marketing premium, consistent, high-quality distillers products. Others offer modified distillers grains — partially dried to 50% dry matter rather than 88-90%, or are adding more solubles back than normal and providing a high-phosphorus product.

“You have to know what you're dealing with,” he warns.

Dry Distillers With Solubles Can Be 30% Of Ration

At least 30% of dry matter in a dairy ration can contain dry distillers grains with solubles (DDGS) and maintain acceptable dry matter intake and milk production and composition, according to recent University of Nebraska-Lincoln research.

Thirty-four mid- to late-lactation cows were offered a control diet without DDGS or one that contained 30% dry matter in the form of DDGS. Diets were formulated to contain similar amounts of crude protein, NDF and energy. Dry matter intake as well as milk production and composition were no different for cows fed DDGS than those fed the control diet.

Wet Vs. Dry Distillers With Solubles

Wet distillers grains with solubles may have an edge over dry products as far as digestibility is concerned — but not much, says David Schingoethe, South Dakota State University (SDSU) dairy scientist.

Dry products, however, can be stored longer and shipped greater distances more economically and conveniently than wet.

Feeding wet products avoids the cost of drying them, but wet normally stays fresh only five to seven days, depending on the weather. There's also more feed loss from surface mold using wet distillers with solubles than from using dry, and added costs of preservatives if used.

Yet, Schingoethe says, some field reports show the wet product can last for up to a year. “We at SDSU successfully stored wet distillers grains with solubles for more than six months in silo bags,” he adds.