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 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 pulps of lemon (LP), grape (GP), and orange (OP) were ensilaged with tannin-degrading bacteria (enzyme activity: 10.46 - 8.60 U mL^-1) isolated from the rumen of male goat (Escherichia coli GHMGHE41), deer (Escherichia fergusonii GHMGHE44), ram (E. fergusonii GHMGHE30), and camel (Klebsiella aerogenes GHMGHE38). After anaerobic incubation (30 days; 39.00 ˚C), PP + camel strain silage showed the highest dry matter, and the lowest natural acid detergent fiber and pH. The camel strain increased crude protein content of LP silage to the highest level, and decreased acid detergent fiber of GP silage to the lowest level. The highest digestibility was observed for LP + goat strain silage (50.37%) compared to the uninoculated OP silage (42.73%). The maximum ammonia (N-NH₃) and minimum level of pH were recorded for the silages of LP + goat strain and PP + CR strain, respectively. Overall, the current results showed that tannin-degrading E. coli GHMGHE41 and K. aerogenes GHMGHE38 were able to improve the digestibility of LP and PP silages as ingredients in ruminants' diets.