EFFECTS OF SOYBEAN HULLS AND LIGNOSULFONATE-TREATED SOYBEAN-MEAL ON RUMINAL FERMENTATION IN LACTATING DAIRY-COWS

Four Holstein cows were used in a 4 x 4 Latin square design to investi gate the effects of soybean hulls and lignosulfonate-treated soybean m eal on ruminal fermentation and nutrient passage to the duodenum. Diet s contained 32% com silage, 19.8% alfalfa-grass hay, and 48.2% concent rate (DM basis). Treatments, arranged in a 2 x 2 factorial, were conce ntrate mixes based on 1) corn and soybean meal, 2) com and treated soy bean meal, 3) soybean hulls and soybean meal, and 4) soybean hulls and treated soybean meal. Individual protein supplements supplied 40% of dietary CP, and com or soybean hulls constituted 28% of dietary DM. In take of OM (mean 18.9 kg/d) was similar among treatments, but intake o f NDF was 42% greater, and intake of nonstructural carbohydrate was 55 % less, for cows fed soybean hulls. Passage of OM to the duodenum was similar among diets, but flow of NDF was 43% greater, and flow of nons tructural carbohydrate was 56% less, for cows fed soybean hulls. Rumin al pH was similar, but total concentrations of VFA increased 7% when s oybean hulls replaced com. Ruminal digestion of dietary CP was 15% les s for cows fed treated soybean meal, but bacterial N flows were simila r among treatments. Soybean hulls were digested to a similar extent as com, but few interactions occurred between supplemental carbohydrate and protein sources.