Abstract
The current study has two objectives: (1) To determine the effect of different lactic acid bacteria (LAB) strains’ inoculant on silage quality of fresh ryegrass (FR) and rain-treated ryegrass (RTR), and (2) to find the optimal way (silage inoculant vs. direct-fed microbial (DFM)) to use LAB strains in order to improve nutrient digestibility and reduce methane emission (CH4) in ruminant production. Five LAB strains were tested, Lactiplantibacillus plantarum AGR-1, L. plantarum AGR-2, Lactococcus lactis subsp. lactis biovar diacetylactis AGR-3, L. lactis subsp. lactis AGR-4 and L. lactis subsp. lactis AGR-5. Each LAB strain was inoculated at 106 cfu/g fresh weight into the FR and the RTR and ensiled for 60 days. After ensiling, the effect of LAB strains included as a DFM or silage inoculant on rumen digestibility and CH4 production were measured using an in vitro gas production system with three separate runs. The in vitro experiment consisted of 24 treatments (2 grasses (FR and RTR) × 2 ways (inoculant or DFM) × 6 strains (5 LAB strains + 1 Control)). The results indicated that the LAB strains’ inoculant treatments reduced (p < 0.0001) the dry matter (DM) losses, the NH3 concentration (p < 0.0001) and the pH (p = 0.0019) upon ensiling in both the FR and the RTR. The lowest values in dry matter (DM) loss and NH3 concentration were found in the L. plantarum (AGR-2) and L. lactis (AGR-5). The in vitro CH4 production was lower for silages inoculated with L. plantarum (AGR-1, p = 0.0054), L. lactis (AGR-4, p = 0.026), L. lactis (AGR-5, p = 0.029) and L. plantarum (AGR-2, p = 0.090), compared to the control. Methane production was lower (p = 0.0027) for LABs when used as silage inoculants, compared to being used as DFM. Lactic acid bacteria used as silage inoculants increased (p ≤ 0.0001) the in vitro DM and organic matter (OM) degradability both in the FR and the RTR, whereas LAB strains used as DFM showed no such effect. The DM and OM digestibility were highest in the L. plantarum (AGR-1, p = 0.0175). Among the five LAB strains used in the current study, L. plantarum (AGR-2) was the best candidate to improve silage quality. Our observations suggest that these LAB strains are most promising when used as silage inoculants and to be confirmed in vivo.
Highlights
IntroductionAccording to the European Council, greenhouse gas (GHG) emissions have to be decreased over
According to the European Council, greenhouse gas (GHG) emissions have to be decreased over80% in developed countries by 2050 [1]
The fermentation dry matter (DM) (%) loss was lower in the lactic acid bacteria (LAB) inoculant treatments compared to the control (7.39 vs. 12.77, p < 0.0001)
Summary
According to the European Council, greenhouse gas (GHG) emissions have to be decreased over. 80% in developed countries by 2050 [1] In this context, methane (CH4 ) is the second most important gas involved in greenhouse emissions, with CH4 from livestock accounting for 6.3% of the global. In European countries such as the Netherlands, ensiling is the most important method to preserve moist forage used as feed for ruminants [4]. This method is based on natural fermentation, in which lactic acid bacteria (LAB) ferment water-soluble carbohydrates in the plant material into organic acids, mainly lactic acid (LA), under anaerobic conditions. The pH quickly drops, inhibiting detrimental anaerobes and preserving the nutritional value and palatability of the moist forage
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