TOWARD THE DEVELOPMENT OF SOYBEAN-TOLERANT ATLANTIC SALMON Salmo salar LINES

Soybean meal (SBM) stands as viable replacement for fishmeal in aquaculture because of the relatively high protein content, amino acid profile and digestibility, as well as its global availability and low cost.  Unfortunately, to date, SBM inclusion in salmon feed has been rather limited due to poor performance and negative physiological impacts in fish fed SBM-containing diets. However, studies have shown that there is significant individual and family variation in the ability to use SBM derived protein in salmonids, and that this trait has moderately high heritability.  Since adaptability to SBM utilization is heritable, it is possible to develop lines of salmon with increased efficiency in utilizing SBM as a protein source through the use of traditional selective breeding strategies. Marker assisted selection, (MAS) using genetic markers such as single nucleotide polymorphisms (SNPs) associated with traits of interest, can be used to compliment traditional breeding and reduce the time required to achieve genetic gains.

Results will be presented here on a study aimed at using genome-wide association studies (GWAS) to identify Atlantic salmon SNPs associated with increased tolerance to or efficiency in utilizing SBM as a protein source.  A 60-day feeding trial is being conducted to evaluate the effects of two different SBM inclusion levels (Control and Test diets with 5 and 30% SBM, respectively) on weight gain, feed efficiency, body composition, nutrient deposition, and intestinal histology.  Thirty full-sib families (initial body weight: 12.3 ± 1.0 g) of Atlantic salmon (St. John River strain) were utilized for the trial.  Six fish per family were allocated to six different 325-liter tanks so that all families were represented equally in each tank.  Each fish was tagged with passive integrated transponders (PIT); and each diet was allocated to three tanks.  

At the end of the feeding trial, the eight largest and eight smallest fish from both the top five and bottom five performing families in terms of weight gain in each treatment will be selected for whole-body composition analysis, and histological examination of mid and hindgut.  Samples from each fish will subsequently be subjected to high density SNP genotyping. Nutrient deposition and efficiency of utilization as well as intestinal inflammation are phenotypes that will be described quantitatively and correlated with SBM inclusion levels and genotype results.  The expected outcome of this project is a set of SNPs associated with increased tolerance and/or efficiency in utilizing SBM as a protein source.  These novel markers will play a key role in the development of improved genetic lines that will allow for a significant increase in SBM inclusion in aquafeeds for Atlantic salmon.