THE DIGESTION OF GRASS SILAGES PRODUCED USING INOCULANTS OF LACTIC-ACID BACTERIA

The purpose of this study was to evaluate the efficiency of two inocul ants of lactic acid bacteria (LAB) on grass silages. The evaluation wa s made in terms of silage composition, rumen fermentation, digestion a nd animal production. Over a 2-year period two lots of silage were pre pared in two 100-tonne capacity clamps. In each case an untreated sila ge and an inoculant-treated silage were prepared simultaneously from a n identical herbage source using independent sets of silage-making equ ipment. The inoculant used in the first year was Pioneer Brand 1188 (P ioneer Hi-Bred UK), and in the second year a slightly different inocul ant from the same source (Pioneer Hi-Bred) was used. The two inoculant s were essentially similar in composition, comprising a mixture of Lac tobacillus plantarum and Streptococcus faecalis; the strains included in the second inoculant were selected for their capacity to tolerate h igher temperatures. The fermentation of the inoculant-treated silages appeared to be dominated by homofermentative LAB compared with the unt reated silages. The use of either inoculant was associated with a chan ge in the rumen volatile fatty acid (VFA) pattern, with a significantl y greater molar proportion of propionate and a corresponding reduction in both acetate and butyrate. There was a trend indicating an enhance d efficiency of microbial protein synthesis within the rumen of the he ifers for the inoculant-treated silages, although this was only signif icant when concentrate was offered with the silage in one experiment. The inoculant-treated silages had significantly greater intake charact eristics than did the untreated silages, though this was not reflected in a statistically significant improvement in average daily liveweigh t gain in either year.