Miron, J., Institute of Animal Science, Volcani Center, ARO, P.O. Box 6, Bet Dagan, 50250, Israel
Yokoyama, M.T., Department of Animal Science, Michigan State University, Anthony Hall, East Lansing, MI 48824, United States

The effect of ozone treatment on the composition of lucerne hay and on the digestion of total and cell-wall (CW) monosaccharides was examined in vitro, and the changes in the occurrence of the predominant rumen bacterial species involved in whole hays and their CW utilization were determined. The effect of ozone treatment was expressed in a reduction of lucerne CW concentration from 51.5% to 35.6%, destroying 65% of the lignin and solubilizing 53% of CW non-glucose polysaccharides (NGP). Ozone treatment improved the in vitro digestion of dry matter and total monosaccharide components significantly by 15.3 and 21.0% up to 79.5 and 87.6%, respectively. This improvement by ozonation originated from both solubilization of CW monosaccharides and improvement in the digestion of residual CW glucose and CW NGP by 15.5 and 14.9% up to 81.7 and 72.5%, respectively. The changes in the occurrence of the predominant rumen bacterial species grown for 48 h on untreated or ozonated lucerne hays or their CW preparations as the sole substrates were determined using the agar roll-tubes technique. Ozonation increased the total viable count of rumen bacteria by 30% from 1.0 × 109 in untreated hay up to 1.3 × 109 in the ozonated hay. The proportion of the Ruminococci species comprising 70% of the population utilizing untreated hay was reduced to 46% in the ozonated material, while that of Bacteroides ruminicola and Butyrivibrio fibrosolvens increased from 6.66 to 30.7%. When grown on untreated CW preparations, the Ruminococci species and Bacteroides succinogenes were identified in equal proportions (18.2% each), but on the ozonated CW preparations B. succinogenes and B. fibrosolvens were the predominant rumen bacteria, comprising 36.4 and 22.7%, respectively, while proportions of the Ruminococci species and of B. ruminicola were reduced. The feasibility of ozone treatment of lucerne hay, and some of the rumen bacterial mechanisms involved in CW degradation and utilization, are discussed. © 1990.