## 1 Introduction  
Soybean meal (SBM) has been largely investigated and commercially used in fish nutrition. Although SBM offers several advantages to the aquafeed industry including worldwide availability, competitive pricing, consistent nutritional quality, and an acceptable amino acid profile it also displays some constraints, mainly associated with antinutritional factors [1, 2]. There is a long list of antinutritional factors including saponins, lectins,ytic acid, oligosaccharides, isoflavones, and allergens, among others [1]. These antinutrients are known to impair feed intake, palatability, growth performance, digestive enzymes and in some instances induce gut inflammation damaging the mucosal integrity and causing enteritis [1, 3, 4, 5, 6, 7, 8]. The degree of physiological impairments induced by dietary SBM is linked to the SBM inclusion level, blends of raw materials, duration of feeding SBM-based feeds, and the species sensitivity to antinutritional factors [3, 4, 5, 6, 9, 10]. Intestinal damage induced by SBM has been reported mostly in distal intestine and liver tissues across several fish species including Atlantic salmon _Salmo salar_[3, 4, 9, 10], Totoaba _Totoaba medonaldi_[5, 6], Seriola spp _Seriola lalandi, Seriola dorsalis_[7, 11, 12, 13], common Carp _Cyprinus carpio_[14, 15], and Largemouth Bass _Micropterus salmoales_[8]. Distal intestine histology shows changes in the length of the mucosal fold, reduction in the number of supranuclear vacuoles of the enterocytes and thickness of the lamina propria, among other pathohistological modifications [3; 5; 6; 10; 12; 16; 17]. Among the fish species, salmon appears to be one of the most sensitive to the antinutritional factors presented in SBM developing a condition known as soybean meal-induced enteropathy, which exhibits similar changes as those described above [3; 4; 9; 17]. Some salmon species such as pink salmon _Oncorhynchus gorbuscha_ appears to be more resistant to antinutritional factors present in dietary SBM than chinook _O. tshawqtscha_ and Atlantic salmon _S. salar_[18]. In the early 2000's, [PERSON] et al. [19], suggested the binding mechanism of soybean agglutinin (lectin) to Atlantic salmon intestinal epithelium as a primary contributor to pathological changes in this tissue. Saponins are other top candidates of key antinutritional factors present in soybean meal. A dose-response study reported increasing inflammatory process in Atlantic salmon distal intestine with greater dietary soybean saponins [20]. Several strategies have been applied attempting to reduce or eliminate some of the antinutritional factors in SBM including extrusion, fermentation, pre-processing techniques, and genetic engineering. For example, extrusion with shorter barrel retention times and higher temperatures improved utilization of SBM-rich diets (52% SBM) in salmonids [21]. Another commercial strategy is to increase the protein fraction of SBM through concentration (SPC) or isolation (SPI). A relatively small effort has been done in the genetic space focusing on selecting non-GM SBM for specific genotypes in aquafeeds. Recently, the removal of trypsin inhibitor, lectin and allergen P34/Gly m Bd 30 k from a soybean cultivar failed to alleviate inflammatory processes in Atlantic salmon [9]. Collectively, these studies suggest the challenge in identifying specific antinutritional factors present in soybean responsible for enteritis induction and highlight the complexity of interactions with compounds present in other plant ingredients largely used in aquafeed formulations. As a result, the salmon aquafeed industry has adopted ingredient inclusion limits and more processed soy protein products such as soy protein concentrate and isolate. However, from a cost-effective perspective, finding approaches to minimize or eliminate the soybean-induced enteritis in fish nutrition is worthwhile.