EXPELLER SOYBEAN-MEAL AND CORN BY-PRODUCTS VERSUS SOLVENT SOYBEAN-MEAL FOR LACTATING DAIRY-COWS FED ALFALFA SILAGE AS SOLE FORAGE

Production responses obtained with supplemental protein from expeller soybean meal or corn by-products, relative to solvent soybean meal, were determined in three replicated 4 × 4 Latin square trials. Dietary forage (54 to 58% of DM) was solely alfalfa silage containing 30 to 55% DM and 21% CP (DM basis). Main concentrate ingredient was either ground shelled or high moisture corn; diets were fed as total mixed rations. In Trials 1 and 2, supplements were: control (0 CP), .6× (60% of the supplemental CP of the 1× treatment) solvent soybean meal, .6× expeller soybean meal, and 1× solvent soybean meal. In Trial 1 (DM intake = 24.4 kg/d), supplement had no effect on production but increased weight gain; expeller soybean meal increased production of milk and lactose relative to either amount of solvent meal. In Trial 2 (DM intake = 20.0 kg/d), supplement increased production of milk and milk components; milk production on .6× expeller soybean meal was greater than .6× solvent soybean meal. In Trial 3 (DM intake = 22.4 kg/d), distillers dried grains plus corn gluten meal replaced .6× solvent soybean meal; supplement increased production of milk, 3.5% FCM, protein, and fat with no difference among the three proteins. Across all three trials, response to supplemental protein appeared to decrease with increased DM intake. Results indicate that resistant protein from expeller soybean meal and corn by-products can replace greater amounts from solvent soybean meal, and suggest that, despite high dietary CP, absorbed protein supply may be inadequate when alfalfa silage is the sole forage. © 1990, American Dairy Science Association. All rights reserved.