Forages may promote better rumen function than non-forage fiber sources such as distillers' grain.

In a South Dakota State University study, cows were fed a control diet of 45% corn silage, 15% alfalfa hay and 45% concentrate. Three other diets were formulated to replace the corn silage with 7%, 14% and 21% corn distillers' grain. Soybean meal was replaced with soybean hulls as the percentage of distillers' grain increased.

Dry matter intake and milk protein percentage increased with increasing amounts of distillers' grain in the diets. The amount of milk produced was not affected. However, milkfat dropped, indicating that the distillers' grain lacked effective fiber.