Results of a study by Canadian researchers, published in the Jan. 20, 2018, issue of Aquaculture journal, showed that solvent-extracted soybean meal (SBM) at low levels causes soybean meal-induced enteritis (SBMIE) in Atlantic salmon.

The researchers assessed and compared the effects of SBM on intestinal morphology, inflammation and microbiome composition of Chinook salmon (Oncorhynchus tshawytscha), pink salmon (O. gorbuscha) and Atlantic salmon (Salmo salar).

Atlantic, Chinook and pink salmon were fed for three weeks on a diet with 20% inclusion of SBM or a control diet with fish meal. After one week on the SBM diet, Atlantic and Chinook salmon showed increased submucosa thickness in the distal intestine compared with the fish fed on the fishmeal diet.

 

Intestinal inflammation in these species increased over time, with a further increase in submucosa thickness.

After three weeks on the SBM diet, intestinal inflammation was most severe in Chinook salmon. In contrast, pink salmon only showed a slight increase in submucosa thickness, and no significant increase in inflammatory cell infiltrate.

Sequence-based analysis of the intestinal microbiome (total microorganisms and their collective genetic material) showed a significant difference in overall microbiome composition between species, but did not show an effect of the SBM diet on microbiome diversity or composition in any of the three salmon species.

The researchers concluded that SBM-fed Chinook salmon were more susceptible to SBMIE than Atlantic salmon, whereas pink salmon were not susceptible to SBMIE at the levels of SBM tested.

SBM is an attractive protein source for fish feed because of its high protein content, favorable amino acid profile, and low cost.

The study suggested that utility of soybean meal in salmonid diets requires species-specific research on inclusion rate and feeding regimes.