Ileal true digestibility of amino acids in wheat milling by-products for pigs

Ten batches of wheat milling by-products - 3 of wheat middlings (WM), 4 of wheat feed (WF), 3 of wheat bran (WB) - were analysed and studied for their protein and amino acid ileal true digestibility (ITD). Each batch was test ed on four castrated male pigs weighing between 35 and 95 kg, and fitted wi th an end-to-end ileo-rectal anastomosis. In all types of by-products, lysi ne and threonine were among the least digestible amino acids, whereas methi onine was among the most digestible ones. N and all amino acids ITD decreas ed significantly (P < 0.05) from WM to WF and to WE. In WM, the average N, lysine, threonine and methionine ITD values were 93.6, 90.8, 90.4 and 95.1% , respectively. They decreased to 85.5, 86.6, 83.3 and 91.5%, respectively in WF and down to 70.1, 68.3, 68.4 and 78.9%, respectively in WE. N and all amino acids ITD was predicted according to either the ratio of the feedstu ff fibre to amino acid concentrations, or the proportion of total N bound t o the NDF (neutral detergent fibre) residue, or both. For most amino acids, the use of CF (crude fibre), ADF (acid detergent fibre) or ADL (acid deter gent lignin) as fibre criteria provided accurate equations with coefficient of determination higher than 90%.