Effect of ensiling persimmon peel and grape pomace as tannin-rich byproduct feeds on their chemical composition and in vitro rumen fermentation.

This study aimed to evaluate the effects of ensiling fruit byproducts on their chemical composition and in vitro ruminal fermentation. Persimmon peel (PP), white grape pomace (WGP), and red grape pomace (RGP) were ensiled for 1, 2, 4, and 8 weeks. Fresh and ensiled PP, WGP, and RGP were used for in vitro rumen fermentation with or without polyethylene glycol (PEG). The non-fiber carbohydrate (NFC) content of the byproducts decreased after ensiling, especially for PP. The total tannin content was not changed after ensiling for up to 4 weeks for all byproducts. However, the soluble tannin content in PP decreased but that in grape pomaces was unaffected by ensiling. Gas production, total volatile fatty acid concentration, and methane production by in vitro rumen fermentation for PP and WGP were reduced by ensiling, and increased by adding PEG, except for gas production from the PP silage. These results indicated that changes in the fractions of carbohydrate and tannins during the ensiling process were different between PP and grape pomace. Even though the insolubilization of tannins in PP during ensiling reduced its inhibitory effect on ruminal fermentability, the ensiling PP seemed to remain the ability to mitigate methanogenesis in the rumen.