Donald Davis

With current advancements in technology allowing for genetic modification of crops, canola has been modified to contain n3 long-chain polyunsaturated fatty acids such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). The purpose of this study was to determine the efficacy of using genetically modified canola oil as a DHA and EPA replacement for Menhaden fish oil (FO) in practical diets for Pacific white shrimp Litopeneaus vannamei. This trial was conducted using twenty-four 750 L tanks stocked at 40 shrimp per tank (0.1 ± 0.007 g initial weight) and grown for 63 days. Shrimp were fed one of five experimental diets (36% protein, 8% lipid) with supplemental FO replacement varying from 75% to 100% twice daily (7 a.m. and 7 p.m.). Two of the diets contained 15% fishmeal (FM) as the basal protein source, while the other three diets were FM free, allowing for complete removal of DHA sources in the basal formulation. While basal FO was removed, none of the experimental diets were completely devoid of FO. Shrimp were harvested and frozen after 9 weeks to be used for lipid extraction and taste and texture analysis by an untrained panel to mimic consumer responses. Results were subjected to a two-way analysis of variance, with significant differences observed in final mean weight (8.47–10.59 g) ( p = 0.0275 ), individual weight gain (8.37–10.48 g) ( p = 0.0279 ), and weekly gain (0.84–1.05 g) ( p = 0.0378 ). Human sensory analysis did not yield significant differences between measured taste parameters ( p > 0.05 ). Lipid extraction and analysis results showed that fatty acid concentrations from whole shrimp samples correlate with diet lipid profiles except for EPA. There is no significant difference ( p > 0.05 ) in EPA concentrations in whole shrimp samples regardless of diet. These results suggest that Latitude™ oil can be successfully used as a partial replacement for FO in commercial shrimp diets.

Many bacterial pathogens impact the US catfish industry, and disease control can be challenging for producers. Columnaris disease in channel catfish, Ictalurus punctatus , is primarily caused by Flavobacterium covae (formerly F. columnare ). Immunostimulants may enhance nonspecific immune responses and offer an alternative to antibiotic treatments in catfish. Furthermore, dietary protein sources and inclusions are also essential to fish health and nutrition and may enhance overall fish performance in pond culture. The current project evaluated two immunostimulants: a protease complex (PC) and a humic substance (HS) derived from a reed‐sedge peat product. A 60‐day trial examined the effects of five diets on growth performance, immune response and resistance to experimental F. covae infection in channel catfish. Diets included a high‐quality fishmeal diet (32%; CF32), a high‐protein soy‐based diet (32%; C32), a low‐protein soy‐based diet (28%; C28; predominately used in industry), a low‐protein soy diet supplemented with C28 + PC at 175 g metric ton −1 and C28 + HS in a low‐protein diet at 23 g metric ton −1 . Following feeding for 60 d, juvenile channel catfish were sampled for growth performance and baseline health indicators ( n = 3; body mucus, blood for sera, kidney and spleen). A subset of fish was then subjected to an immersion‐based in vivo challenge trial with F. covae (ALG‐00‐530; 10 6 CFU mL −1 exposure). At 60d post‐initiation, there were no dietary differences in the relative growth rate ( p = .063) or thermal growth coefficient ( p = .055), but the 32% diets generally appeared to perform best. Post‐challenge, the C32 group's mortality was higher than the C28 + PC ( p = .006) and C28 + HS diets ( p = .005). Although not significant, the C28 and CF32 groups also demonstrated higher mortality compared to both PC and HS diets. Sera lysozyme concentration was found to increase following pathogen challenge ( p < .001) and in comparison with mock‐challenged catfish ( p < .001). Elevated expression levels of proinflammatory cytokines ( il‐1β , il‐8 , tnf‐α and tgf‐β ) were observed at trial midpoint and post‐infection when compared to 60d. The C28 treatment was found to have lower tnf‐α expression than the C28 + PC ( p = .042) and C28 + HS ( p = .042) groups following exposure to F. covae . These challenge data suggest that the immunostimulants (PC and HS) in plant‐based protein may be beneficial in protecting against F. covae when offered in low‐protein channel catfish diets.