Recovery at the terminal ileum of some legume non‐nutritional factors in cannulated pigs

Abstract

In order to exert an effect, either local or systemic, putative beneficial dietary substances have to survive at least to some extent the digestive process within the gastrointestinal tract. For that purpose, five castrated male pigs (100 ± 2 kg mean live b.w.) fitted with T-shaped ileal cannulas were used to determine the recovery up to the terminal ileum of various non-nutritional factors (NNF) from legumes (defatted soybean, raw lupin, raw chickpea and raw or autoclaved kidney beans). Kidney bean lectin (PHA) recovery within the small intestine ranged between 2.5 and 4.8 mg from 5.96 mg ingested. Two different methods were used to determine ileal digestibility of protease inhibitors (PI) in pigs. According to the enzyme-linked immunosorbent assay (ELISA) method, apparent digestibility of Kunitz trypsin inhibitor and Bowman-Birk inhibitor for pigs fed the defatted soybean-based diet were 0 and 58%, respectively. On the other hand, the apparent digestibility of PI along the small intestine, expressed in terms of trypsin inhibitory activity, was 96, 98 and 95% of activity in the diet, while data expressed in terms of chymotrypsin inhibitory activity were 95, 99 and 79% of activity in the diet for defatted soybean, raw chickpea and autoclaved kidney bean diets respectively. Differences found in ileal digestibility values of PI using both methodologies, ELISA and enzymatic inhibition, might be explained by the detection of inactive forms by specific antibodies. Intestinal apparent digestibility of phytate was 0% for defatted soybean and autoclaved kidney bean diets, whereas values for raw lupin and chickpea diets were 4.1 and 24.5%, respectively. In conclusion, significant amounts of several NNF survived the passage through the stomach and small intestine of cannulated pigs, which might have biological relevance.

Active Bowman–Birk inhibitors survive gastrointestinal digestion at the terminal ileum of pigs fed chickpea‐based diets

“…Although immunoassays offer the specificity and sensitivity necessary to recognise BBI proteins in complex samples,18, 29 they have some limitations in comparison with the enzymatic methods. Antibody‐based enzyme‐linked immunoabsorbent assays (ELISA) can be misleading, particularly in assays of samples from the GIT where some protein digestion is expected, and immunoreactive BBI forms may be detected that are not functional 18, 19. In addition, unusual patterns of temperature‐dependent binding displayed by monoclonal antibodies towards soybean BBI have been reported; even mild thermal treatment of samples seems to significantly affect the affinity of soybean BBI and specific antibodies 30.…”

“…Using the Kjeldahl method, crude protein content of feed was determined as N × 6.25 for hydrolysed casein and N × 5.5 for chickpea proteins 23. Other chemical determinations were carried out as previously described 19…”

“…Purified soybean ( Glycine max ) BBI and a soybean BBI concentrate exerted a protective effect in dimethylhydrazine (DMH)‐treated animals, reducing the incidence and frequency of colon tumours in mice15, 16 and rats,17 without any adverse side effects documented for animal growth or organ physiology. Although such studies have demonstrated potential health benefits of BBI proteins within the GIT, there have been very few attempts to quantify the intestinal recovery of BBI proteins and results are controversial mainly due to methodological difficulties 18, 19. The presence of high levels of trypsin‐ and chymotrypsin‐like proteases in ileal flows makes it particularly difficult to accurately evaluate the inhibitory activity of these samples by enzymatic methods; additionally, BBI proteins have a strong affinity for the digestive enzymes, trypsin and chymotrypsin and, under neutral conditions, are likely to be complexed with the proteases they inhibit.…”

Biochemical characterization of legume seeds as ingredients in animal feed

“…According to Rubio et al (2006) intestinal apparent digestibility of phytate was 0% for defatted soybean and autoclaved kidney bean in pigs diets, whereas the values for raw lupin and chickpea diets were 4.1 and 24.5%, respectively. As the monogastric organism contains no or only negligible amounts of endogenous phytase in the stomach and small intestine, it is dependent on plant or microbial phytase to hydrolyse these compounds.…”