The utilization of Fish Meal (FM) as a protein source in the Aquaculture industry has been shown not to be sustainable. Soybean meal (SBM) is a potential 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.
Two presentations at the Aquaculture America 2017 meeting (February 17-22, 2017) took a new approach to increasing the acceptance of SBM in salmon diets. These studies were based on the observation that there are 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, 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 of a study aimed at using genome-wide association studies to identify Atlantic salmon genomic markers associated with increased tolerance to or efficiency in utilizing SBM as a protein source were reported. The 60-day feeding trial was 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 of about 12 g) of Atlantic salmon were utilized for the trial. Six fish per family were allocated to six different tanks so that all families were represented equally in each tank. Each fish was tagged 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 were selected for whole-body composition analysis and histological examination of mid and hindgut. Tissue samples from families presenting poor and good growth when fed a high SBM diet were selected and DNA was extracted.
The result of this research study using some highly sophisticated genomic approaches identified seven SNPs (in 5 different chromosomes) as being significantly correlated with growth. These markers had an average R-squared of 0.09 and explained roughly 9% of the estimated heritability of growth of Atlantic salmon when fed diets containing high levels of soybean meal. These markers, if validated with additional research, may be useful in breeding programs and facilitate higher inclusions of soybean meal in commercial diets for Atlantic salmon.