A comparative study on in vitro and in vivo stomach–small intestinal and large intestinal digestion of plant protein meals in growing pigs

This experiment evaluated the difference between computer-controlled simulated digestion and in vivo stomach-small intestinal or large intestinal digestion for growing pigs. Five diets including a corn-soybean meal basal diet and four experimental diets with rapeseed meal (RSM), cottonseed meal (CSM), sunflower meal (SFM), or peanut meal (PNM) were assigned to each group of five barrows installed terminal ileal cannula or distal cecal cannula in a 5 × 5 Latin square design. Ileal digesta and feces were collected for the determination of digestibility of dry matter (DM) and gross energy (GE) as well as digestible energy (DE) at terminal ileum and total tract. The large intestinal digestibility and DE were calculated by the difference between measurements obtained at the terminal ileum and those obtained from total tract. In vitro stomach-small intestinal digestibility and DE for diets and plant protein meals were determined by stomach-small intestinal digestion in a computer-controlled simulated digestion system (CCSDS). The in vitro large intestinal digestibility and DE of diets were determined in a CCSDS using ileal digesta and enzymes extracted from cecal digesta of pigs. The in vitro large intestinal digestibility and DE of four plant protein meals were determined by the difference between stomach-small intestinal and total tract digestion in the CCSDS. For the experimental diets, the in vitro ileal digestibility and DE were not different from corresponding in vivo values in basal diet and PNM diet, but greater than corresponding in vivo values for diets with RSM, CSM, and SFM (P < 0.05). No difference was observed between in vitro and in vivo large intestinal digestibility and DE in five diets. For the feed ingredients, the in vitro ileal digestibility and DE did not differ from corresponding in vivo ileal values in RSM and PNM but were greater than the in vivo ileal values in CSM and SFM (P < 0.05). The in vitro large intestinal GE digestibility and DE were not different from in vivo large intestinal values in RSM, CSM, and PNM, but lower than in vivo large intestinal values in SFM. This finding may relate to the higher fiber content of plant protein meals resulting in shorter digestion time of in vivo stomach-small intestine thus lower digestibility compared to in vitro, indicating it is necessary to optimize in vitro stomach-small intestinal digestion time.Comparable in vitro and in vivo values are crucial to develop a novel in vitro digestion technique for growing pigs. The current study evaluated the difference between computer-controlled simulated digestion and in vivo stomach–small intestinal or large intestinal digestion for growing pigs. Five diets including a corn–soybean meal basal diet and four experimental diets with rapeseed meal (RSM), cottonseed meal (CSM), sunflower meal (SFM), or peanut meal (PNM) were used to compare the in vitro and in vivo digestion. Our study demonstrated that the in vitro ileal digestibility of energy was not different from corresponding in vivo values in basal diet and PNM diet, but greater than corresponding in vivo values for diets with RSM, CSM, and SFM. The in vitro stomach–small intestinal digestibility was greater than in vivo digestibility, resulting in less digestible substrates hydrolyzed by in vitro large intestinal fluid, whereas more digestible substrates can be digested by in vivo large intestine in plant protein meals. This difference may relate to the higher fiber content of plant protein meals resulting in shorter digestion time of in vivo stomach–small intestine thus lower digestibility compared to in vitro. Therefore, it is necessary to optimize in vitro stomach–small intestinal digestion time.