Effects of ensiling pistachio by-products on ruminal fermentation and methane emission mitigation using in vitro batch fermentation

The present study was conducted to examine the effects of sun dried and ensiled pistachio by-product (PBP) on fermentation and methane emission in the rumen using an in vitro batch fermentation system. For this purpose، fresh PBP were ensiled into a trench silo without any additives and simultaneously some sun dried PBP were prepared. After 3 month، the ensiled PBP samples were freeze-dried and then chemical analysis was conducted for both samples. All samples were incubated with four replications using buffered rumen fluid for 24 hours. Two positive controls (i. e.، oaten chaff and commercial concentrate) were included in the assay as standards to detect differences. At the end of incubation gas pressure، pH and total volatile fatty acids were used as indicators of overall sample fermentability، and concentrations of methane، ammonia، acetate and propionate indicated changes in fermentation end products. The result showed that the ensiled PBP had lower aNDFom and water soluble carbohydrates but greater in phenolic compounds compared with the sun dried PBP. Gas production were lower (P<0. 01) in sun dried and ensiled pistachio by-products than the oaten chaff and commercial concentrate، although the amounts of volatile fatty acids and ammonia for both PBPwere lower (P<0. 01) than the commercial concentrate. The lowest acetate to propionate ratio and the highest pH were in ensiled PBPhowever، a significant reduction (P<0. 01) in methane emission was observed with both PBP samples in comparison to the positive controls. In general، these findings indicate that PBP has a great potential to decrease methane mitigation and can used as a new alternative for modify of rumen fermentation