TOLERANCE OF GROWING PIGS TO TRYPSIN AND CHYMOTRYPSIN INHIBITORS IN CHICKPEAS (CICER-ARIETINUM) AND PIGEONPEAS (CAJANUS-CAJAN)

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-1 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-1) of the diets were, respectively, control, 0.2; chickpea meal 1, 1.2-3.2; chickpea meal 2, 1.7-4.7; pigeonpea meal, 1.4-3.6. Chymotrypsin inhibitor levels (mg g-1) of the diets were, respectively, control, 0.2; chickpea meal 1, 0.9-2-2; chickpea meal 2, 1.6-4.5; pigeonpea meal, 0.8-2.1. 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-1 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.