AbstractThis study was conducted to examine the nutritional and physiological consequences of feeding young broilers with four commercially obtained full fat soyabean (FFSB) products (all within the tolerated range of trypsin inhibitor activity (TIA, mg/g); sample A, 3.4; sample B, 1.7; sample C, 3.6; and sample D, 1.1). The FFSB samples were fed at 3 inclusion levels of 200, 400 and 600 g/kg in semisynthetic diets. An inert marker, titanium dioxide, was included in the diet (5 g/kg diet). Each experimental diet was fed to 6 pairs of birds for 6 days (starting at 19 days of age). Following slaughter at 25 days of age, pancreas weight relative to body weight was recorded, and ileal digesta samples were examined for amino acids. The concentration of titanium dioxide was also measured in the digesta. The pancreas weight:body weight ratio was affected by FFSB, and by increasing the rate of inclusion (ROI). Chicks fed with diets containing samples A and C showed greater pancreatic enlargement than chicks fed with diets containing samples B and D. The content of ileal digestible amino acids increased with ROI in all samples. Assessment of linear and non-linear contrasts showed that there was a linear response of digestible amino acid content to ROI for all amino acids considered (cysteine, methionine and lysine). The coefficient of apparent digestibility was highest in sample A for all amino acids and lowest in sample C. The occurrence of trypsin inhibitors in plants (especially in soyabeans) and its role in the physiological processes of plants, as well as the antinutritional effects of trypsin inhibitors and how it can be reduced in plant food products are discussed.