Lactobacillus plantarum effects on silage fermentation and in vitro microbial yield

In four parallel experiments, herbage [three harvests of alfalfa (308 to 379g dry matter (DM)/kg), one of whole-plant corn (331 g DM/kg)] was ensiled with three different treatments: no inoculant (control), Lactobacillus plantarum (LP) or formic acid (FA), in 1-L mini-silos and fermented for 60 d at room temperature (22 degrees C). Mini-silos were opened and analyzed for fermentation characteristics and soluble N fractions. A subsample of wet silage from each mini-silo was ground to 4 mm and stored at -20 degrees C. Silages were thawed and subjected to 9 h ruminal in vitro incubations to measure gas production and volatile fatty acid (VFA) production as well as microbial biomass yield (MBY) and microbial non-ammonia N (MNAN) formation using N-15 as a marker. In all four experiments, silage fermentation products and indicated good preservation across all treatments. Analysis of data showed that FA- and LP-treated silages had lower concentrations of ammonia-N and free amino acids N than control. The FA treatment was lower in soluble N, but higher in peptide-N, than control. Silage pH was lowest in FA (4.25), followed by LP (4.28), and control (4.38). Ruminal in vitro gas production and VFA concentrations were not different among treatments (P>0.05). Compared to control, FA- and LP-treated silage yielded greater MNAN and MBY. These findings suggested that L. plantarum preserved more true protein during silage fermentation than control, which in turn increased in vitro ruminal microbial growth. Published by Elsevier B.V.