Effect of tannin-degrading bacteria isolated from the rumen of some ruminants on the in vitro digestibility and gas production of fruits residues silage

Abstract

While severe shortage of feed has presented livestock industry with a major challenge, millions of tons of fruit by-products (FBPs) are discarded annually, as valuable sources of energy and numerous nutrients. However, some of FBPs contain high tannins that must be treated for use in animal feeding. This study was investigated the effect of tannin-degrading bacteria (TDB) isolated from the rumen of some ruminants on the in vitro digestibility and gas production of FBPs silage. The FBPs including pomegranate peel (PP), and the pulp of lemon (LP), grape (GP), and orange (OP) were ensilaged with TDB (enzyme activity:10.46-8.60 U/mL) isolated from the rumen of male goat (GR; Escherichia coli GHMGHE41), deer (DR; E. fergusonii GHMGHE44), ram (RR; E. fergusonii GHMGHE30), and camel (CR; Klebsiella aerogenes GHMGHE38). After anaerobic incubation (30 d, 39 ℃), PP+CR strain silage was shown the highest dry matter (DM), and the lowest natural acid detergent fiber (NDF) and pH (P<0.05). The CR strain increased crude protein (CP) content of LP silage to the highest level, and decreased acid detergent fiber (ADF) of GP silage to the lowest level (P>0.05). The highest digestibility was observed for LP+ GR strain silage (50.37%) compared to uninoculated OP silage (42.73%). The maximum ammonia (N-NH3) and minimum level of pH were recorded for LP+GR additive and PP+CR strain, respectively (P<0.05). Overall, the current results showed that tannin-degrading Escherichia coli GHMGHE41 and Klebsiella aerogenes GHMGHE38 were able to improve the digestibility of LP and PP silage as ingredients in ruminant diets.