Abstract
Lucerne and two maize crops were ensiled with and without Lactobacillus plantarum and fermented for 4 or 60 d to assess the effect of inoculant on in vitro rumen fermentation of the resulting silages. Water and 80% ethanol extracts of the silages were also analysed for effects on in vitro rumen fermentation. The inoculant affected lucerne silage characteristics but had little effect on the maize silages. In vitro fermentation of the silages showed few effects except increased microbial biomass yield (MBY) at 24 h in the inoculant-treated lucerne silages. In vitro fermentation of the lucerne silage water extracts produced no differences due to treatment except for reduced MBY in the inoculant-treated extracts. The ethanol extracts produced results inconsistent with the in vitro results of the silages. Consequently it appears that the factor in in vitro fermentation of inoculated silages causing increased MBY was in neither the water nor ethanol extracts.
Highlights
Microbial silage inoculants are additives used to improve silage fermentation (Muck and Kung 1997)
Sometime inoculants reduce the amount of fermentation products, and that should have a positive effect on milk production
LP-treated Maize-LDM at 4 d was similar to control (5.07 and 4.90 g kg-1 DM, respectively), but at 60 d it was greater than control (15.09 and 9.69 g kg-1 DM, respectively); in contrast in the other two crops, no effects of treatment were observed at day 4 or 60
Summary
Microbial silage inoculants are additives used to improve silage fermentation (Muck and Kung 1997). The most common silage inoculants contain facultative heterofermentative lactic acid bacteria (LAB) that shift fermentation toward lactic acid production, reducing acetic acid and ethanol. That is correlated to higher milk production; a 10 g kg-1 N reduction in ammonia would be expected to increase energy-corrected milk by 0.19 kg d-1 (Huhtanen et al 2003). The expected improvement in milk production from all of these shifts in silage composition are much less than the observed average improvement in milk production (1.4 kg d-1) from feeding inoculated silage (Kung and Muck 1997). Changes in common silage characteristics due to silage inoculant use cannot explain the magnitude of improvements in milk production observed
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