A metabolism trial was conducted to evaluate the digestibility rate and energy values of thermal processed soybean for growing pigs. Twenty barrows with an initial average weight of 37.67± 3.33kg were used in a completely randomized design with five treatments and four replicates. The treatments consisted in a reference diet and four experimental diets. The feedstuffs evaluated were soybean meal, extruded semi-integral soybean, expanded integral soybean and micronized integral soybean. These ingredients replaced 25% of the reference diet. The values of digestibility energy and apparent digestibility rates of crude energy, crude protein, dry matter and ether extract of the feeds were: 3583kcal/kg, 85.2%, 90.8%, 85.7% and 69.3% for soybean meal; 4065kcal/kg, 83.6%, 86.1%, 81.9% and 81.5% for extruded semi-integral soybean; 3803kcal/kg, 75.2%, 73.9%, 74.4% and 80.4% for expanded integral soybean; 5272kcal/kg, 95.3%, 95.2%, 93.2% and 94.3% for micronized integral soybean. The expansion process was not adequate for integral soybean, which showed the worst digestibility rate. The extrusion and the micronization processes of semi-integral and integral soybean respectively, were efficient to inactivate the antinutritional factors and to improve the digestibility. The results obtained with the micronization process were better than those of the others thermal processes.
soybean; digestibility; antinutritional factors; micronization; extrusion; expansion