EVALUATION OF A NEW HIGH-PROTEIN VARIETY OF SOYBEANS AS A SOURCE OF PROTEIN AND ENERGY FOR DAIRY-COWS

Twenty Holstein cows in midlactation were used in a Latin square desig n to evaluate the nutritional quality of a high protein soybean (CP 45 %) fed raw or roasted. Treatments were 1) control (soybean meal); 2) c onventional soybean (Maple Isle), raw; 3) conventional soybean, roaste d; 4) high protein soybean (AC Proteus), raw; and 5) high protein soyb ean, roasted. Diets were formulated to be isonitrogenous and consisted of approximately 10% whole crop barley silage, 15% corn silage, 19% a lfalfa silage, 31% rolled barley, 17% cracked corn, and from 6.5 to 8. 6% of the appropriate protein source on a DM basis. Replacement of con ventional soybean with the high protein soybean increased milk and mil k component yields. Ah soybean treatments lowered milk protein percent ages versus soybean meal although milk protein yield was only reduced for the raw Maple Isle soybean treatment. Milk fat percentage was redu ced for the roasted AC Proteus soybean treatment versus soybean meal a nd both Maple Isle soybean treatments, although,total milk fat yield d id not differ among treatments. Heat treatment by roasting tended to a ffect total milk yield positively for both types of soybeans, but only the increase for Maple Isle was significant. Milk from cows fed full fat soybeans had more long-chain fatty acids than milk from cows fed s oybean meal. Roasting the soybeans further increased the amounts of lo ng-chain fatty acids. The new high protein soybean, AC Proteus, appear s to be an excellent source of supplemental protein and energy for lac tating dairy cows.