Apparent and standardised true ileal digestibility of protein and amino acids from faba bean, lupin and pea, provided as whole seeds, dehulled or extruded in pig diets

Two trials were performed to measure the apparent ileal digestibilities (AID) of amino acids (AA) in eight legumes (two faba beans and two lupins batches in experiment 1, four peas in experiment 2) and to estimate their standardised true ileal digestibility (SID). The effect of dehulling was investigated in one faba bean batch rich in tannins (experiment 1) and the effect of extrusion on one winter pea batch rich in trypsin inhibitor (experiment 2). In experiment 1, dietary dry matter AID was significantly lower with lupins than with faba beans. However, AA AID and SID were generally higher in the Australian lupin than in faba beans. Tryptophan AID (66.7) was lowest with the Alfred faba bean and increased by 20% after dehulling of the seeds up to the value obtained with the Australian lupin. Cystine (AID 55.5, SID 65.1) and tyrosine (AID 74.7, SID 78.1) were the other least digestible AA in the Alfred faba bean and digestibility did not improve significantly after dehulling. Lysine SID was lower (P<0.05) in the Lublanc lupin (81.4%) than in the dehulled Alfred and Blandine faba beans and in the Australian lupin, which were very close (88.1, 88.8 and 88.4, respectively.). In experiment 2, dietary dry matter AID was significantly higher (P<0.01) in the extruded Frilène pea than in all other peas including the untreated Frilène (77.6 versus 70.8). The same was true for protein (SID 89.1 versus SID 77.6) and the sum of AA (SID 91.6 versus SID 80.1). The most important relative improvements were noted for tryptophan (+31.3% for AID) and cystine (+38% for SID). Compared to European spring peas (Amino, Finale), quite low AID values were observed in the Australian and Frilène peas for methionine (61.5, 64.2), threonine (62.6, 65.3), tryptophan (54.7, 57.6) and cystine (56.1, 53.4), while lysine AID were higher (79.6, 77.6). After correction for basal endogenous losses, the sulphur amino acids, methionine (SID 68.7, 70.4) and cystine (SID 66.0, 62.8) remained the least digestible amino acids in the Australian and Frilène pea. These data allow relating nutritional value to species and variety, in terms of their ANF contents, and demonstrate the efficiency of technological treatments.