Distillers grains - a byproduct of ethanol production - may serve as supplemental dairy cattle feed to boost milk and milk fat yields, while reducing feed costs. But the challenge is to determine what type of distillers grains are most effective and how much can be fed.
Ohio State University Extension dairy specialists are evaluating the impacts of DGS (distillers grains with solubles) on milk fat levels in a cow's diet and seeking explanations as to why those levels vary across different diet scenarios. Researchers are specifically focusing on diets with Rumensin. Rumensin is a common feed additive that sometimes depresses milk fat yields.
"Farmers use Rumensin because it increases feed efficiency. In dairy cattle, it increases milk production and in beef cattle it improves gain," says Maurice Eastridge, an OSU Extension dairy specialist. "But Rumensin can decrease milk fat, which impacts yields and that means less in a farmer's pocket. We are concerned about that profitability."
Eastridge and his colleagues are evaluating how different diets alter the composition of milk fatty acids and trying to explain why that is happening under those specific dietary conditions. The researchers are focusing on DGS because of its high fat content. Concentrations of protein, fiber, fat, and minerals are generally about three times higher in distiller grains than in corn.
However, the amount of fat in the distillers grain may be the limiting factor on how much can be fed without adversely affecting milk yield or composition.
"Compared with other feeds, the nutrient composition of distillers grains is more variable than the average feed," says Bill Weiss, a dairy nutrition specialist with the Ohio Agricultural Research and Development Center. "Using feeds that are highly variable can reduce profitability of livestock operations because of increased feed costs or reduced production."
DGS is being added to six dietary scenarios that involve ground corn, long and short hay, and Rumensin. Researchers are focusing on two different types of distillers grains, including one high in fat and one high in protein and low in fat.
"DGS is a possible source of supplemental feed to add fat to the diet," says Eastridge. "The question is how far can farmers push the upper limit of DGS use that is profitable for them and healthy for the cow."
Researchers expect to have some results by this fall.
Farmers have been feeding distillers grain to livestock since the turn of the century, but the growing demand for ethanol production is increasing DGS supply and availability. The annual production of distillers grains was about 1 million tons in 1998. By 2006, that number had risen to 10 million tons. Estimated production by 2010 is 16 million tons.