Effect of trypsin inhibitor activity in soybean on the growth performance, protein digestibility and incidence of sub-clinical necrotic enteritis in broiler chicken flocks

International audienceABSTRACT 1. The effect of three different levels of dietary trypsin inhibitor activity (achieved by varying the amount of non-toasted full fat soybean in replacement for toasted full fat soybean) on the incidence of spontaneously-occurring sub-clinical necrotic enteritis in broiler chickens was compared. A fourth dietary treatment compared the effect of a diet that used potato protein concentrate as the major protein source. The determined trypsin inhibitor activity increased with the increasing level of non-toasted soybean: 1.90, 6.21, 8.46 and 3.72mg/g for the three soybean diets (0,100g/kg and 200g/kg of non-toasted soybean) and the potato protein diet respectively. 2. Although increasing levels of the non-toasted full-fat soybean increased the food intakes of the birds (P<0.05), there was a marked reduction (P<0.001) in protein digestibility, weight gain and feed conversion efficiency. 3. There was a linear increase (P<0.001) in sub-clinical NE lesions in the duodenum, jejunum, mid small intestine and ileum with increasing non-toasted soybean. Caecal Clostridium perfringens counts increased with the increasing dietary levels of non-toasted soybean. Serum α-toxin antibodies were higher (P