Impact of ferulic acid esterase producing lactobacilli and fibrolytic enzymes on conservation characteristics, aerobic stability and fiber degradability of barley silage

Abstract

The objective of this study was to determine the effects of applying ferulic acid esterase (FAE) producing inoculants or non-FAE inoculants in combination with exogenous fibrolytic enzymes (EFE) at ensiling on silage characteristics and nutritive value of whole barley crop (Hordeum vulgare). Barley (330 g DM/kg fresh crop) was harvested at early-dough, chopped and allocated to one of the following four treatments: untreated (Control), FAE producing Lactobacillus buchneri mixture inoculants (T1), none-FAE L. buchneri mixture inoculants (T2), and T2 plus EFE (T3). Inoculants were applied at 1 × 108 colony forming units/gram forage (cfu/g) and EFE at 424 U (xylanase) and 180 U (endoglucanase)/kg fresh weight. Forage was packed into 12 laboratory silos per treatment and ensiled for 7, 28 and 90 d. Subsamples at 90 d were used for in vitro, in situ and aerobic stability studies. After 90 d of ensiling, all inoculated silages had less (P < 0.001) water soluble carbohydrate, and greater (P < 0.001) DM loss as compared to the Control. For T1 and T2, aNDF was greater (P = 0.003) than Control and T3 silage. From d 0 to d 7 of ensiling, 16S rRNA copy numbers of L. buchneri in Control increased from 6.5 to 8.0 log10 copies/g, thereafter remaining stable, whereas it increased from 7.0 to 10.0 log10 copies/g in all inoculated silages, reaching ∼10.5 log10 copies/g after 28 d of ensiling. At this time, inoculated silages also had a higher (P < 0.001) pH, produced more acetic acid and ethanol, but less (P = 0.01) lactic acid than Control. After 21-d aerobic exposure, all inoculated silages remained stable, but Control silage deteriorated as indicated by a reduction (P < 0.001) in lactic acid and an increase (P < 0.001) in pH, and numbers of yeast. The T3 silage had less (P < 0.001) total gas production than other silages in in vitro ruminal fermentation. Compared to Control, the soluble fraction (a) of DM was less (P < 0.001) in T1 and T2, whereas it was greater (P < 0.001) in T3 silage. In situ NDF digestibility of T1 silage was greater (P < 0.01) than that of Control and T3 silage at 24 and 72 h of incubation. Inoculation of whole crop barley silage with inoculants containing FAE or non-FAE producing L. buchneri improved ruminal NDF digestibility, but a combination of EFE with a none-FAE L. buchneri reduced NDF degradability.