Apparent total tract digestibility and ileal digestibility of dry matter, nitrogen, energy and amino acids in conventional, Bacillus subtilis-fermented and enzyme-treated soybean meal fed to weanling pigs

Apparent total tract digestibility (ATTD), apparent ileal digestibility (AID) and standardised ileal digestibility (SID) of dry matter, nitrogen, energy and amino acids were evaluated in six weanling barrows [(Landrace × Yorkshire) × Duroc] fed soybean meal diet (SBM), fermented soybean meal A diet with 50% solubility in potassium hydroxide (FSMA), fermented soybean meal B diet with 60% solubility in potassium hydroxide (FSMB), fermented soybean meal C diet with 70% solubility in potassium hydroxide (FSMC), enzyme-treated soybean meal (ETSM) and nitrogen-free diet. Pigs having body weights of 8.99 ± 0.40 kg were surgically equipped with T-cannulas of approximately 15 cm prior to the ileo-cecal junction and randomly allotted to one of five dietary treatments and a nitrogen-free diet in 6 × 6 Latin squares. With regards to the ATTD of essential amino acids, the ATTD of arginine, isoleucine, lysine, methionine and total essential amino acids was greater in pigs fed FSMB, FSMC, and ETSM diets than in SBM and FSMA diets. The ATTD of leucine, phenylalanine, threonine and valine in the FSMC diet was non-significant compared with the values of ATTD in FSMB and ETSM diets. With respect to non-essential amino acids the ATTD of aspartic acid, cysteine, glutamic acid, proline, tyrosine and total amino acids was greater in pigs fed the FSMC diet compared with the SBM diet and not different from the values of pigs fed the ETSM diet. The AID of dry matter, nitrogen and energy in the FSMC diet was greater (P < 0.05) than in pigs fed SBM and FSMA diets but was equal to the values of FSMB and ETSM diets. With regards to the AID of essential amino acids, the AID of histidine, lysine, methionine and threonine was greater in pigs fed FSMB, FSMC and ETSM diets than in SBM and FSMA diets (P < 0.05). The AID of isoleucine was greater in pigs fed FSMB and ETSM diets than the FSMA diet. The AID of arginine, phenylalanine and valine was greater in pigs fed the FSMC diet compared with the SBM diet. With respect to non-essential amino acids the AID of aspartic acid, glutamic acid, glycine, tyrosine and total amino acids was the same as in pigs fed FSMB, FSMC, ETSM diets and greater (P < 0.05) than in pigs fed SBM and FSMA diets. The SID of all essential amino acids in pigs fed the FSMC diet was greater than for the FSMA diet. In the case of non-essential amino acids, the SID of all amino acids except for cysteine was greatest in pigs fed FSMB, FSMC and ETSM treatments. In conclusion, dietary supplementation of FSMB, FSMC and/or ETSM diets can improve the ATTD, AID and SID of dry matter, nitrogen, energy, total amino acids and most of the essential amino acids in weanling pigs.