Polyethylene glycol improves in vitro digestibility and fermentability of nutrients for pigs by binding with tannins in sorghum grain

This experiment was conducted to determine the effects of polyethylene glycol (PEG) supplementation on the digestion and fermentation characteristics of sorghum nutrients in the in-vitro simulated porcine gastrointestinal tract. In Exp. 1, high-tannin sorghum grain without or with 50 mg/g PEG was digested by porcine pepsin and pancreatin to measure in-vitro digestibility of nutrients. In Exp. 2, the lyophilised porcine ileal digesta from barrows fed the high-tannin sorghum grain without or with 50 mg/g PEG and the undigested residues from Exp. 1 were, individually, incubated with fresh pig caecal digesta as inoculums for 48 h to simulate the porcine hindgut fermentation. PEG reduced the detectable condensed tannin content by 32% (p < .05) and increased in-vitro digestibility of nutrients especially for crude protein(p < .05). The in-vitro fermentability of nutrients and microbial metabolites including the accumulative gas production excluding the first 12 h, total short-chain fatty acid and microbial protein content in the fermented solutions were improved (p < .05). The relative abundance of Lachnospiraceae NK4A136 was both increased by PEG supplementation regardless of unhydrolyzed residues (p < .05) or ileal digesta (p = .06) as fermentation substrates. In conclusion, PEG supplementation not only directly increased the chemical enzymatic digestion of nutrients in the simulated anterior intestine, but also directly promoted the microbial fermentation including microbial diversities and metabolites in the simulated posterior intestine of porcine. It implies that the increased abundances of Lachnospiraceae by PEG in the hindgut may improve the fermentation capacity of microbiota and thus increase the nutrient digestion in the hindgut.