Pea protein concentrate substituting fish meal or soybean meal in diets for Atlantic salmon (Salmo salar)-Effect on growth performance, nutrient digestibility, carcass composition, gut health, and physical feed quality

The effect of pea protein concentrate in diets for Atlantic salmon on growth performance, nutrient digestibility, carcass composition, blood chemistry, histology of the gastro-intestinal tract (GIT), and physical feed quality was investigated. A 12-week study was conducted using triplicate groups of Atlantic salmon with 0.16 kg initial weight kept in seawater. The dietary treatments consisted of one control diet based on high-quality fish meal (FM diet), one control diet containing 200 g kg− 1 soybean meal (SBM diet), and two experimental diets containing 200 g kg− 1 pea protein concentrate with either 350 or 500 g kg− 1 crude protein (PPC 35% CP and PPC 50% CP diet), substituting for fish meal protein. There were no significant differences among dietary treatments for weight gain or feed intake, but there was a tendency (P < 0.07) toward a lower feed conversion ratio in fish fed the PPC 50% CP diet. There were no differences in the digestibility of protein, fat, starch and most essential amino acids between the fish fed the FM and the PPC 35% CP or PPC 50% CP diets, but the PPC diets gave lower energy digestibility. The SBM diet gave reduced digestibility for protein, fat, starch, essential amino acids, and energy compared with the FM and the PPC diets. Also, feeding the PPC diets had no effect on body composition, while the SBM diet reduced (P < 0.05) the content of carcass fat and energy compared with the FM diet. Feeding the PPC diets did not induce morphological changes in the intestine, or affect the size of the GIT. Brush border maltase activity and fecal trypsin activity were unaffected. Feeding the SBM diet increased the size of the stomach, decreased the size of the distal intestine (DI), induced morphological changes in the DI, reduced brush border maltase activity, and increased fecal trypsin activity compared with the FM and PPC diets. In conclusion, pea protein concentrate was shown to be a promising new protein ingredient for salmonids and could replace 20% of high-quality fish meal protein in the feed without any adverse effect on growth performance, carcass composition or histology of the DI.