Determination of chemical composition and metabolizable energy of chickpea, faba bean, field pea, lentil and lupin compared to soybean meal for broiler chickens

The chemical composition, apparent metabolizable energy (AME) and nitrogen-corrected apparent metabolizable energy (AMEn) of lupin, faba bean, field pea, lentil, chickpea and soybean meal were determined for growing broilers. Grain legumes were incorporated into experimental diets either raw or after being steam-conditioned at 80°C for 30 seconds. Assay diets were developed by replacing (w/w) 300 g/kg of formulated basal diet (maize-soybean meal) with one of the legumes (raw or heat-treated) or soybean meal (test sample). Each assay diet was randomly allocated to 4 replicates (8 birds per cage) and fed in mash form for 7 d (d 14 - 21 post-hatch). Feed intake and total excreta were measured in the last 4 days of the trial. Among the grain legumes, starch content was lowest in lupin (4.3 g/kg) and highest in field pea (425 g/kg). Apart from lupin, grain legumes were greater in starch than soybean meal. Crude fat of soybean meal (13.5 g/kg) was lower than that of faba bean (14.1 g/kg), field pea (18.6 g/kg), lupin (47.2 g/kg) and chickpea (58.3 g/kg), but greater than lentil (10.9 g/kg). The gross energy of grain legumes ranged from 4,275 Kcal/kg (field pea) to 4,681 kcal/kg (lupin), and that of soybean meal was 4,514 Kcal/kg. Heating of grain legumes had no effect on AME and AMEn, except for lupin, where it increased by 23.9 and 23.5 %, respectively. The AME values among the raw legumes, were highest in lentil (2,438 Kcal/kg) and lowest in lupin (1,595 Kcal/kg), with the intermediate values for chickpea (2,206 Kcal/kg), faba bean (1,923 Kcal/kg) and pea (1,970 Kcal/kg). The AME of raw legumes were lower (P< 0.05) than that of soybean meal (2,673 Kcal/kg), but N-corrected AME of lentil was not different to that of soybean meal. The current results showed that steam conditioning at 80°C was not effective to improve energy availability of grain legumes, except for lupin. Soybean meal is superior to grain legumes in terms of energy availability for broiler feeding.