A β-mannanase experiment was conducted to determine the efficacy of supplementation to corn-soybean meal based diet on ileal digestibility of nutrients and amino acids in growing pigs. Twenty barrows with an average body weight of 25 kg were surgically fitted with an ileo-cecal cannula. The treatments compared corn based conventional or de-hulled SBM supplemented diets with or without 400U β-mannanase/kg. The cannulated pigs were allotted to one of 4 dietary treatments plus a nitrogen-free diet in a completely randomized design with 4 pigs per treatment. The nitrogen-free diet was used to determine basal endogenous losses of crude protein and amino acids. Each experimental period consisted of 7 d of diet adaptation followed by total feces and ileal digesta collection.

Results indicated that adding 400U β-mannanase/kg to the pig’s diet improved (P < 0.05) apparent ileal digestibility (AID) of dry matter compared to non-supplemented diets containing conventional SBM (80.9% vs. 77.2%) and in de-hulled SBM (83% vs. 79.5%). The mannanase supplementation did not influence N and GE digestibility. The AID of threonine and proline was higher (P < 0.05) in dehulled SBM (81.3%, 82.6%) compared to conventional SBM (77.3%, 78.0%). Likewise, the SID (standardized ileal digestibility) of threonine and proline was higher (P < 0.05) in dehulled (87.3%, 83.9%) compared to conventional SBM (83.9%, 80.3%). The supplementation of mannanase led to higher (P < 0.05) AID of amino acids such as arginine (78.2, 79.6% vs. 74.0, 75.5%), histidine (82.2, 83.2% vs. 79.0, 81.5%), lysine (84.6, 86.9% vs. 79.4, 80.1%), valine (78.2, 80.2% vs. 74.3, 76.7%) and glycine (81.2, 82.9% vs. 77.1, 80.3%) in conventional and dehulled SBM than non-supplemented diet and higher (P < 0.05) SID of lysine (89.0, 89.8% vs. 84.2, 87.0%) in conventional and dehulled SBM than non-supplemented diet.