Effects of condensed tannins on bacterial and fungal communities during aerobic exposure in sainfoin silage

Abstract

Sainfoin is a forage legume that is widely distributed around the world and is beneficial for animals owing to the characteristics of its condensed tannins (CTs), which, from certain plants, can prolong the aerobic stability of silage. The present study investigated whether sainfoin CTs can prolong aerobic stability by adding polyethylene glycol (PEG) to inactivate CTs activity in the silage system. The results showed that the aerobic stability increased under the PEG treatment (P < 0.05). The pH (4.62 vs. 4.53; P < 0.05) was lower while the ammonia nitrogen (0.71 g ammonia nitrogen/kg dry matter (DM) vs. 0.94 g/kg DM; P < 0.05) was higher in the PEG-treated group compared with the control after 3 d of aerobic exposure. The crude protein content decreased by 5.93% in the PEG-treated group during 7 d of aerobic exposure. BA was detected only in the PEG-treated group upon aerobic exposure. Yeasts were more abundant in the control compared with the PEG-treated group after 7 d of aerobic exposure (4.32 vs. 4.08 Log10 CFU/g, fresh weight basis, P < 0.05), after which the relative abundance of Lactobacillus was lower in the PEG-treated group (65.01% vs. 75.01% in the control; P < 0.05), while the relative abundance of Pediococcus was higher in the PEG-treated group compared with the control (10.9% vs. 4.49%, respectively; P < 0.05). Wickerhamomyces was dominant in both groups after 7 d of aerobic exposure, with no difference between groups (P > 0.05). The relative abundances of Apiotrichum and Aspergillus were lower in the control than in the PEG-treated group after 7 d of aerobic exposure (2.28 vs. 8.63% for Apiotrichum and 0.58 vs. 7.19% for Aspergillus, respectively; P < 0.05). The results suggested that sainfoin CTs decreased aerobic stability, but could inhibit certain bacteria and fungi, such as Pediococcus and Apiotrichum, and preserve the protein content during the aerobic exposure of silage.