EFFECTS OF DIETARY FORAGE SOURCE AND AMOUNT OF FORAGE ADDITION ON INTAKE, MILK-YIELD, AND DIGESTION FOR LACTATING DAIRY-COWS

Lactating cows were used to determine the effects of increasing forage content from alfalfa (Medicago sativa L.) hay or Tifton 85 bermudagra ss (Cynodon sp.) hay on dry matter intake (DML), milk yield, and nutri ent digestion. Forage proportions and neutral detergent fiber (NDF) co ntent of diets were (dry basis) 1) 45% corn (Zea mays L.) silage (cont rol), 33.5% NDF; 2) 15% bermudagrass hay and 30% corn silage, 39.5% ND F; 3) 30% bermudagrass hay and 15% corn silage, 46.6% NDF; 4) 15% alfa lfa hay and 30% corn silage, 35.5% NDF; or 5) 30% alfalfa hay and 15% corn silage, 33.5% NDF. The DMI was greater with alfalfa diets than wi th bermudagrass diets, with low hay diets than with high hay diets, an d with the control diet than with tile hay diets. Digestibility of NDF in bermudagrass diets was greater than that in alfalfa diets, in high hay diets than in low hay diets, and in hay diets than in the control diet. In vitro NDF digestion was most rapid for bermudagrass hay, int ermediate for corn silage, and slowest for alfalfa hay. Results sugges t that NDF from bermudagrass was digested more completely and rapidly than was NDF from corn silage or alfalfa, which improved the rate of p assage despite the high NDF content of diets containing bermudagrass. Milk yield followed trends for DMI. The control diet and diets contain ing alfalfa elicited the greatest DMI and milk yield, but DMI per 100 kg of body weight for Holsteins was equal for diets containing either bermudagrass or alfalfa. High quality bermudagrass can be used in rati ons Ear lactating dairy cows.