SULFUR DIOXIDE AS A PRESERVATIVE FOR LEGUME-GRASS SILAGE

Abstract

Alfalfa-bromegrass or alfalfa-bromegrass-timothy forage was treated with SO2 as a silage preservative at levels of 0, 0.14, 0.36 and 0.66% of the fresh forage weight while filling eight concrete stave silos (2.4 m in diameter × 6.1 m high). There was retention in the silage of 38–59% of the applied SO2. Although SO2 treatment did not (P > 0.05) influence silage pH or have a consistent effect on temperature, the ammonia N content of the silage was reduced (P < 0.01) from 10.9% of the total N in the control silage to 5.2% of the total N in the silage treated with 0.66% SO2. Silage acetate and lactate concentrations were also lowered (P < 0.01) by SO2 treatment. Butyrate and ethanol concentrations were very low and not (P > 0.05) affected by the preservative. The silage conserved with SO2 and hay harvested from the same fields were assessed using 80 steers in a feeding trial of 55 days. SO2 treatment had no consistent effect on dry matter intake; however, the rates of gain of the steers fed silage preserved with 0.36 and 0.66% SO2 were 26 and 23% higher (P < 0.05), respectively, than those of steers fed untreated silage. Feed dry matter to gain ratio decreased (P < 0.05) from 12.5 to 9.3 as the SO2 treatment level was increased from 0 to 0.66%. There were no differences (P > 0.05) in rate of gain, dry matter intake or the feed to gain ratio between steers fed hay and those fed the silage without SO2 treatment. It was concluded that SO2 exhibited potential as a good silage preservative when applied at rates of between 0.36 and 0.66% of the forage weight.