Atlantic salmon (Salmo salar) parr as a model to predict the optimum inclusion of air classified faba bean protein concentrate in feeds for seawater salmon

Faba bean (Vicia faba) is a legume with good potential that has previously been tested in fish species with some promising results. The present study aimed to determine whether an air-classified faba bean protein concentrate (BPC, 615 g kg− 1 crude protein content) could offer improved or favourable growth performance, body composition and gut health compared to commercially used protein sources such as FM and soy protein concentrate (SPC) in Atlantic salmon (Salmo salar). The trial investigated the performance of 16 feeds formulated with varying FM/SPC/BPC proportions using a mixture design approach. Salmon parr of average weight of 1.47 g were used as a model. The trial lasted eight weeks and also included high FM (560 g kg− 1) and high defatted soybean meal (SBM, 360 g kg− 1) feeds as negative and positive controls respectively, for the assessment of enteritis in the distal intestine. The effects on growth performance, body nutrient composition, survival and fish health, specifically gut histology, were determined. The results demonstrated conclusively that total inclusion levels of BPC ranging from 50 to 200 g kg− 1, partially replacing SPC and/or FM, displayed the greatest potential to be beneficial in terms of fish performance and nutrient composition with increased growth, protein content, fat content and ash. In addition to favourable whole-body composition parameters, it was found that inclusions of BPC below 340 g kg− 1 of feed did not cause detrimental effects such as the enteritis observed in fish fed the high soybean meal control. High inclusion level (447.2 g kg− 1) of BPC caused a mild inflammation that was not as severe as that caused by the feed with high SBM. The results of this screening study indicate that BPC derived from faba beans can be a valuable alternative protein source in Atlantic salmon feeds. The data provided a platform to model the optimum range of BPC inclusion levels in combination with FM and SPC for further investigation in commercially relevant fish and conditions.