Increased nitrogen secretion by inclusion of soya lectin in the diets of pigs

Abstract A study was conducted with 12 castrated male pigs of 13 kg average body weight (BW) to investigate the metabolic flow of purified soya lectin (SL) incorporated in pig diets in low and high doses and their effect on nitrogen (N) passing the terminal ileum. The pigs were fitted with a post‐valvular T‐caecum cannula and two indwelling blood catheters. They were daily fed 500 g of a corn‐starch‐based semi‐synthetic diet, free or supplemented with low or high doses of purified lectin. To determine the proportion of endogenous N on the amount of total N passing the terminal ileum, the 15 N‐isotope dilution method was used. The amount of dietary ingested total lectins, determined by an ELISA method, recovered in the stomach was reduced from 177 and 1065 mg kg −1 of dry matter (DM) to 4.53 and 28.70 mg kg −1 of DM for the low lectin (LL) and high lectin (HL) diets, respectively. The concentration of lectins in mg kg −1 of DM in stomach and ileal digesta were at a similar level for LL and HL diets. The concentration of functional lectins as determined by the FLIA method (i.e. lectins capable of carbohydrate binding) were estimated in gastric digesta at 2.51 and 21.52 mg kg −1 of DM for LL and HL diets, respectively. They could not be detected in ileal digesta. The daily ileal DM and total N flow was significantly increased ( P < 0.05) when feeding the HL diet, as compared with the lectin‐free (control) and LL diets. The dietary inclusion of purified lectin increased ( P < 0.05) the daily flow of endogenous N at the terminal ileum. With LL and HL containing diets, the ileal N flow were increased to 0.14 and 0.62 g day −1 , respectively, when compared to a control diet. Endogenous N passing the terminal ileum was increased by 0.33 and 0.51 g day −1 for LL and HL diets, respectively. In addition, the production of volatile fatty acids which appeared in the ileal digesta, in particular acetate and proprionate was increased in the pigs that were fed with the lectin‐containing diets.