Soy lecithin is a valuable co-product of soy oil extraction that can be used as a feed additive for aquafeeds. The supplementation of soy lecithin has shown improvement in the growth performance of several aquatic species, including channel catfish. The first proposed study seeks to evaluate an optimal level of soy lecithin in catfish feeds (0, 0.5, 1, 1.5, 2, and 2.5%) for growth performance and how this supplement can influence the stress, intestinal microbiota, and disease resistance against a pathogenic bacteria (Edwardsiella ictaluri). The second proposed study aims to translate the findings from the first study to field conditions, where fish will be fed three experimental extruded feeds containing either soy lecithin-supplemented feed, a positive control, and a negative control (what is currently being practiced by the industry). Production numbers and an economic evaluation will be conducted for the second study to analyze if there is profitability and the margins that this ingredient may bring for the catfish industry. The findings of these proposed studies will allow a better understanding of the physiological responses of dietary lecithin and provide a picture of how this supplement can perform in practical conditions.

• This study will determine if there is an optimal level of inclusion of soy lecithin to catfish feed in laboratory conditions by analyzing the production performance, stress responses, intestinal microbiota, and disease resistance. The optimal inclusion level of soy lecithin will be tested in practical conditions with extruded feed and rearing the animals in earthen ponds. The production performance and preliminary economic analysis will be performed.
• Results will be analyzed using statistical models and interpreted for the different variables analyzed in the first proposed study. The second study will evaluate the practicality of supplementing soy lecithin in farming conditions. The economic feasibility of supplementing soy lecithin improved production performance and possibly increased disease resistance will dictate the success or failure of the proposed project.
• The results generated from the proposed studies will be directly delivered to catfish and soybean stakeholders to present the possibilities and prospective beneficial effects of soy lecithin supplementation for farmed catfish.

Update:
Experimental diets were manufactured using ingredients donated by the local catfish feedmills. Ingredients were ground using a hammermill, mixed and feed was cold pelleted and dried overnight. Crude soy lecithin was kindly provided by Joe (Long Zou, Bungee). Diets were stored at -20 C until used.

Regrettably, a power outage occurred in mid-May, resulting in the unfortunate loss of a significant portion of the naïve juvenile channel catfish population from the Research Station at Mississippi State University. Consequently, we found ourselves with an insufficient number of specimens to execute the originally proposed study encompassing six distinct dietary treatments (ranging from 0% to 2.5% soy lecithin) and six replicates. As a solution, the feeding trial was streamlined to encompass five dietary treatments from 0% to 2.0%, and each treatment had replicated tanks. Six hundred and twenty-five channel catfish juveniles (~6.8 g) were equally distributed in 25 aquaria (110-L), and fish will be offered their dietary treatments.

Update:
Preliminary report 2:

Naïve channel catfish juveniles were obtained from the Thad Cochran National Warmwater Aquaculture Center and moved to the catfish nutrition laboratory. Fish were acclimated for a week prior to commencing the feeding trial. Seven hundred and fifty catfish juveniles (~4.5 grams) were equally distributed in 25 glass aquaria (110-L) operating as a recirculating system. Five experimental diets were formulated to meet all established nutrient requirements for channel catfish, and soy lecithin was included at 0, 0.5, 1.0, 1.5, and 2.0% at the expense of soybean oil. Experimental diets were analyzed using the procedures suggested by the AOAC (Table 1). Fish were fed rations twice daily according to their body weight, and the tank biomass was weighed every two weeks. Rations were also adjusted daily according to the feeding activity. This is the 9th week of feeding for this experiment, and it is expected to be terminated on the 10th week. Water quality parameters were measured thrice a week, and results were within range for catfish culture: Temperature: 27.0 ± 1.17 °C; Dissolved oxygen: 7.65 ± 0.39 mg/L; pH: 8.28 ± 0.14; Salinity: 1.01 ± 0.38 mg/L; Total ammonia nitrogen: 0.27 ± 0.19 mg/L; Total nitrite nitrogen: 0.03 ± 0.03 mg/L.

Results
Preliminary data for production performance and survival can be found below (Table 2). There is a numerical increase in growth performance and better feed efficiency for fish fed diets at 1.5% and 2.0%. However, it is not statistically significant. Production performance parameters will be calculated at the end of the feeding trial, and condition indices will be collected. The remaining fish will be subjected to a stress challenge, where fish will be exposed to handling, and cortisol will be measured in plasma. Additionally, fish digesta microbiome will be sampled shortly after.

View uploaded report

Update:

View uploaded report 2

Updated April 3, 2024:

• If proven efficacy improves the production performance of catfish and alleviates stress, or disease resistance, the supplementation of soy lecithin will be a preferable source of lipids for catfish diets, not only from the nutritional standpoint but also as a nutraceutical supplement.
• The catfish feed industry sells ~500,000 tons of feed per year, which can be an attractive market for soybean co-products. If proven beneficial, the inclusion of 1% of crude soy lecithin could represent an outlet of sales of ~5,000 tons/year. In addition, by possibly decreasing the feed conversion ratio of catfish or increasing the production performance when this animal is reared in ponds, catfish farmers will have higher profitability for their enterprises. This will ultimately strengthen the American Aquaculture industry, which could allow them to re-expand their production systems in the future and consume more U.S. manufactured feed