Abstract:The threshold level of growing pigs to trypsin and chymotrypsin inhibitors was investigated by adding graded levels of meals rich in these inhibitors to diets and recording responses. Diets were formulated to contain either 250, 500 or 750 g kg-' of Opal chickpea, dehulled Tyson chickpea or dehulled pigeonpea meals and pig response compared to that of pigs given a wheat and soya-bean meal control. Trypsin inhibitor levels (mg g-l) of the diets were, respectively, control, 0.2; chickpea meal 1, 1.2-3.2; chickpea meal 2, 1.74.7; pigeonpea meal, 1.43.6. Chymotrypsin inhibitor levels (mg g-') of the diets were, respectively, control, 0.2; chickpea meal 1, 0.9-2.2; chickpea meal 2, 16-45; pigeonpea meal, 08-2.1. The diets were offered ad libitum over the 20-50 kg growth phase. Growth responses of the pigs fed the two chickpea meals were similar to those of the pigs fed the control soya-bean meal diet (P > 0.05). In contrast, the addition of pigeonpea meal linearly depressed growth rate (P < 0.001), feed intake (P < 0.05) and increased the feed conversion ratio (P < 0.05). inclusion levels of the chickpea meals had no effect on organ weights, whereas the inclusion of pigeonpea meal significantly affected the weights of the liver and pancreas (P < 0.05), indicating the presence of other anti-nutritional factors. The results indicate that the growing pig can tolerate dietary levels of at least 4.7 and 4.5 mg g-' of trypsin and chymotrypsin inhibitors, respectively. These threshold levels are unlikely to be exceeded in conventional diets containing the majority of grain legumes. The results also indicate that dehulled pigeonpea meal contains an anti-nutritional factor(s) for growing pigs.

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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 cornstarch-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 15N-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-' of dry matter (DM) to 4.53 and 28.70 mg kg-' of DM for the low lectin (LL) and high lectin (HL) diets, respectively. The concentration of lectins in mg kg-I 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-' 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 c 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-', respectively, when compared to a control diet. Endogenous N passing the terminal ileum was increased by 0.33 and 0.51 g day-' 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.

Twenty-two chickpea samples (7 genotypes, 4 desi and 3 kabuli) representing three different sites of cultivation and three years of harvest were examined for their inhibitory activities against bovine, porcine and human trypsin/chymotrypsin, and compared for their isoinhibitor patterns. No significant difference in inhibitor activity between the desi and kabuli seed types was found for any of the enzymes used, when data from different locations and years were averaged. However, some significant differences were observed between individual cultivars when compared at the same location and in the same year. Inhibitor activities against the three trypsins and three chymotrypsins were statistically different with activities against bovine (5.46f 1.21) > porcine (5.24+ 1.18) > human (4.45 f 0.93) trypsin and those against bovine (4.89 f 1.27) c porcine (8.91 k2.14) < human (10.54f2.50) chymotrypsin (meansf standard deviation, expressed as mg active enzyme completely inhibited per g seed meal). Levels of activity of both trypsin and chymotrypsin inhibitor were influenced by the location and year of cultivation. Isoelectric focusing yielded identical inhibitor patterns for all samples, indicating seven isoinhibitors acting against trypsin and chymotrypsin. Results are discussed in relation to nutritional significance of these inhibitors and perspectives for breeding genotypes low in protease inhibitors.

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