National Center for International Research on Animal Gut Nutrition, Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China.
J Anim Sci. 2023 Jan 3;101. doi: 10.1093/jas/skad126.
The site and extent of digestion of sorghum nutrients affected by tannins in the intestine are not clarified. Porcine small intestine digestion and large intestine fermentation were simulated in vitro to determine the effects of sorghum tannin extract on the digestion and fermentation characteristics of nutrients in the mimicked porcine gastrointestinal tract. In experiment 1, low-tannin sorghum grain without or with 30 mg/g sorghum tannin extract were digested by porcine pepsin and pancreatin to measure in vitro digestibility of nutrients. In experiment 2, the lyophilized porcine ileal digesta from 3 barrows (Duroc × Landrace × Yorkshire, 27.75 ± 1.46 kg) fed the low-tannin sorghum grain without or with 30 mg/g sorghum tannin extract and the undigested residues from experiment 1 were, individually, incubated with fresh pig cecal digesta as inoculums for 48 h to simulate the porcine hindgut fermentation. The results revealed that sorghum tannin extract decreased in vitro digestibility of nutrients both by pepsin hydrolysis or pepsin-pancreatin hydrolysis (P < 0.05). Although enzymatically unhydrolyzed residues provided more energy (P = 0.09) and nitrogen (P < 0.05) as fermentation substrates, the microbial degradation of nutrients from unhydrolyzed residues and porcine ileal digesta were both decreased by sorghum tannin extract (P < 0.05). Regardless of unhydrolyzed residues or ileal digesta as fermentation substrates, microbial metabolites including the accumulative gas production excluding the first 6 h, total short-chain fatty acid and microbial protein content in the fermented solutions were decreased (P < 0.05). The relative abundances of Lachnospiraceae AC2044 and NK4A136 and Ruminococcus_1 was decreased by sorghum tannin extract (P < 0.05). In conclusion, sorghum tannin extract not only directly decreased the chemical enzymatic digestion of nutrients in the simulated anterior intestine, but also directly inhibited the microbial fermentation including microbial diversities and metabolites in the simulated posterior intestine of pigs. The experiment implies that the decreased abundances of Lachnospiraceae and Ruminococcaceae by tannins in the hindgut may weaken the fermentation capacity of microflora and thus impair the nutrient digestion in the hindgut, and ultimately reduce the total tract digestibility of nutrients in pigs fed high tannin sorghum.
高粱养分在肠道中的消化部位和程度受单宁的影响尚不清楚。本研究通过体外模拟猪的小肠消化和大肠发酵，以确定高粱单宁提取物对模拟猪胃肠道中养分消化和发酵特性的影响。试验 1 中，用猪胃蛋白酶和胰酶消化低单宁高粱籽粒，添加或不添加 30 mg/g 高粱单宁提取物，以测定体外养分消化率。试验 2 中，将 3 头（杜洛克×长白×约克夏，27.75±1.46 kg）去势公猪的回肠末端可消化部分和试验 1 的未消化部分分别与新鲜猪盲肠内容物作为接种物在 48 h 内进行孵育，以模拟猪后肠发酵。结果表明，单宁提取物通过胃蛋白酶水解或胃蛋白酶-胰酶水解均降低了养分的体外消化率（P<0.05）。尽管未酶解残渣作为发酵底物提供了更多的能量（P=0.09）和氮（P<0.05），但单宁提取物降低了未酶解残渣和猪回肠可消化部分中养分的微生物降解（P<0.05）。无论作为发酵底物的是未酶解残渣还是回肠消化部分，发酵液中微生物代谢产物（不包括前 6 h 的累积产气量）、总短链脂肪酸和微生物蛋白含量均降低（P<0.05）。单宁提取物降低了发酵液中lachnospiraceae AC2044、NK4A136 和 Ruminococcus_1 的相对丰度（P<0.05）。总之，单宁提取物不仅直接降低了模拟前肠中养分的化学酶消化，而且直接抑制了包括猪模拟后肠微生物多样性和代谢物在内的微生物发酵。该试验表明，在后肠中，单宁降低lachnospiraceae 和 ruminococcaceae 的丰度可能削弱了微生物菌群的发酵能力，从而损害后肠中的养分消化，最终降低猪对高单宁高粱养分的全肠道消化率。
