Ben-Ghedalia, D., Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan, 50250, Israel
Yosef, E., Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan, 50250, Israel

Untreated and sulfur dioxide-treated wheat straw (WS) were used as additives for ensiling low dry matter (DM) lucerne in laboratory silos. The negative control (L + WS) consisted of 60% lucerne + 40% untreated WS on a DM basis. SO2-treated WS was added to the lucerne at 2 levels: 40% (L + 40% TWS) and 50% (L + 50% TWS) of the mixture DM. Lucerne wilted to reach the DM content of the above-mentioned mixtures (30%), was ensiled and served as the positive control (WL). Silos were opened after 90 days and the silages subjected to analyses. The highest DM loss (∼ 10%) was in the negative control (L + WS), whereas in the L + TWS silages DM loss was reduced to 0.5-4%. Lactic acid production was lower in the negative control (L + WS) because of the lack of fermentable sugars and in the L + 50% TWS because of the initial low pH of the mixture at ensiling (4.3). The greatest ability to preserve forage protein was found in the L + 50% TWS, in which nearly 80% of the protein was recovered after 90 days of fermentation, as compared with 43% in the L + WS and WL silages. Threonine and the basic amino acids were extensively degraded in the L + WS silages. The recovery of those amino acids was significantly higher in the L + TWS silages. Generally, the L + 50% TWS was the most successful treatment in preserving the forage amino acids. The concentration of phenylalanine was remarkably increased in silages which underwent extensive protein breakdown (L + WS and WL). In view of its ability to preserve energy and protein, SO2-treated WS could be considered as a future silage additive for direct ensilage of high quality, low DM forages. © 1989.