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.