Response to High-Lysine Proteins to Supplement Diets Based on Distillers Dried Grains plus Solubles for Lactating Cows

Three experiments were performed to evaluate production responses of dairy cows fed distillers dried grains plus solubles (DDGS) supplemented with other protein sources. In Exp. 1 and 2, identical DDGS were used, at 0 to 18.7% of dietary DM in Exp. 1 and at 13 or 18.2% in Exp. 2. The source of DDGS in Exp. 3 was different. Experiments 1 and 2 used alfalfa silage as the sole forage, whereas Exp. 3 included corn silage. Adding blood meal to the DDGS diets improved performance similarly in Exp. 1 and 2. The basal DDGS diet did not respond to additional RDP but was responsive to added Lys. The diets containing DDGS plus blood meal did not respond to supplemental rumen-protected Met or Met plus Lys. However, adding blood meal to the DDGS diets did not result in production equal to the positive control diet containing both blood meal and soybean meal. In Exp. 3, diets with DDGS at 13 and 18% of dietary DM were supplemented with Aminoplus (Ag Processing Inc., Omaha, NE), a soy-based source of RUP. Diets with DDGS at 18% of dietary DM were also supplemented with commodity soybean meal, blood meal, blood and fish meal, or Aminoplus and blood meal. No significant differences were found across treatments for DMI; milk yield; milk protein, fat, and lactose; milk fat percentage; or protein percentage. Diets with DDGS as the primary protein supplement can respond to supplemental Lys, as Lys or blood meal, but the source of DDGS can influence the magnitude of the response.