EFFECTS OF SULFUR DIOXIDE ON THE NUTRITIVE VALUE OF SILAGE FOR STEERS

Abstract

Four experiments are described in which the effectiveness of SO2 as a forage treatment before ensiling was evaluated in terms of its influence on silage composition and nutritive value. Retention of added S to the time of feeding was 40% in one experiment and ranged from 17 to 32% in another experiment where SO2 was either applied in the field or at the silo. In general, more water-soluble carbohydrates were preserved in SO2-treated silage. Across all experiments the acetate concentration was reduced (P < 0.05) from 1.7 to 0.9% in the treated silage dry matter (DM). SO2 had no consistent effect on concentrations of other end products of microbial fermentation. In five experiments with legume or alfalfa-grsss silages the apparent digestibility of energy was increased (P < 0.05) by an average 2.6 percentage units whereas DM digestibility was not influenced (P > 0.05) by SO2 treatment. In contrast, energy (P < 0.05) and DM digestibilities were decreased when two cereal silages were treated with SO2. Cattle fed legume or legume-grass silage grew an average of 12.9% faster (P < 0.05) and exhibited a 12.7% improvement (P < 0.05) in DM conversion to liveweight gain in eight comparisons which have been made with SO2-treated forage to date. In contrast SO2 had no influence (P > 0.05) on the performance of steers in one 42-day trial with cereal silage. Further, SO2 was successfully applied in the field as well as at the silo and addition of a silage inoculant to SO2-treated forage was of no value. The use of SO2 as a preservative for legume and alfalfa-grass silage would be economically feasible under some circumstances but at this time treatment of cereal silages with the chemical cannot be recommended. Key words: Sulfur dioxide, silage, silage preservative, steers, nutritive value