Digestibility of macronutrients, energy and amino acids, absorption of elements and absence of intestinal enteritis in Atlantic salmon, Salmo salar, fed diets with wheat gluten

Apparent digestibility coefficients (ADCs) of macronutrients and energy, an d apparent absorption coefficients (AACs) of amino acids and elements were assessed in an experiment with 0.9 kg Atlantic salmon reared in saltwater t anks. Duplicate groups of fish were fed five diets, where 0, 6.25, 12.5, 25 and 50% of crude protein (CP) from fish meal (FM) was replaced with CP fro m wheat gluten (WG). In Experiment 2, triplicate groups of 0.9 kg salmon we re fed a FM diet, a diet with 15% of CP from FM replaced with extracted, to asted soybean meal (SBM), and a diet with 35% of CP from WG, for 18 weeks. Experiment 2 was designed to determine whether WG caused pathological chang es in the intestinal epithelium, and if a diet with 35% of CP from WG could support rapid growth. There was a trend toward increased ADC of fat and en ergy in the diets with WG, and the diet with 25% WG was ranked significantl y higher than the FM control. The ADC of CP and AACs of all amino acids exc ept alanine and lysine increased significantly with increasing proportion o f dietary protein from WG, and the results indicate that absorption of indi vidual amino acids from WG was between 94% and 100%, WG is low in lysine, b ut the results indicate that the requirement for lysine was nearly met and the requirement for other essential amino acids was met even with the highe st WG inclusion level, due to high dietary protein concentration and the su pplementary amino acid profile of FM. There was no reduced absorption of Ca , P or Mg in the salmon fed diets with WG. The absorption of Zn was higher in all the diets with WG than in the FM diet. The fish doubled their weight during Experiment 2, and there were no significant differences in growth a mong dietary treatments in salmon fed the WG, FM or SBM diets. No indicatio n of intestinal pathology was seen in the salmon fed the FM or WG diets, wh ile 60% of the examined fish fed SBM had SBM-induced changes in the mucosa of the posterior intestine. (C) 2000 Elsevier Science B.V. All rights reser ved.