OPTIMIZING WARM WATER AQUACULTURE: DIETARY SUPPLEMENTS, AND TEMPERATURE EFFECTS ON GROWTH, HEALTH AND MICROBIOME
Abstract
With the rise of the global population, the increasing food demand has led to the intensification of farmed aquatic animal production. These intensified practices require substantial resources, including specialized feed and water. The high demand for fish protein strains production systems, leading to higher stocking densities and increased stress on fish. Additionally, these aquaculture practices have increasingly become unsustainable due to their high resource demand and environmental impact. This affects warm water aquaculture worldwide and in the southern USA. To find solutions to the unsustainable aquaculture practices, four independent studies were conducted to explore new technologies with the effects of dietary supplements on the growth, health, and microbiome of two major warm water aquacultural species in the USA. Biofloc technology is an innovative technology that can be used to propagate warm water aquatic species. It is based on the mass production of heterogenous microorganisms that are beneficial to aquatic species and maintain the carbon and nitrogen ratio of the system. Some of the advantages of biofloc systems include good water quality conditions, reduced water usage, increased biosecurity, and reduced feed conversion ratio. This closed aquaculture system provides environmental and production advantages that will be well suited for the growing food demands. To further explore the application of biofloc systems, the first trial was conducted to investigate how probiotics as dietary supplements influence the growth and health of Nile tilapia. Nile tilapia are well adapted to biofloc systems. This study evaluated the effects of the two commercial probiotics, AP193 and BiOWiSH FeedBuidler Syn 3 on growth parameters, disease resistance and innate immunity of Nile tilapia. When the fish were challenged with a common Nile tilapia pathogen (Streptococcus iniae), the probiotic-fed fish had enhanced disease resistance. However, growth was not affected by the probiotics fed to the fish. This study gave us insights into the fact that applying dietary supplements in biofloc systems might be a sustainable approach to provide extra protection to aquatic species reared in intensified systems. The second study was conducted to optimize the functions of the biofloc system by combining biofloc systems with hydroponic systems. Nile tilapia and romaine lettuce were grown in a biofloc integrated decoupled aquaponic system. Two health-promoting dietary feed additives, a protease complex and a humic substance, were used as treatment groups. Although no growth differences were observed, the feed additive-treated romaine lettuce exhibited higher chlorophyll content. The microbiome of Nile tilapia fecal samples, biofloc water, and root samples were also examined. The application of health-promoting additives have positively influenced microbial diversity, indicating the benefits of using health-promoting dietary additives in aquaponic systems. The subsequent study further explored aquaponic systems with other microbe-derived dietary supplements. Two commercial postbiotics with fermented yeast products (DVAQUA and NutriTek) were used. This study also revealed no differences in Nile tilapia and romaine lettuce growth. Still, it showed increased survival rates in Nile tilapia when challenged with another bacterial pathogen (Flavobacterium oreochromis). Significant variations in various alpha diversity indices (Shannon diversity index, Chao1, and observed species) of fecal and root microbial communities were also observed, emphasizing the influence of yeast-derived supplements on aquaponic systems. A final study focused on channel and hybrid catfish to optimize production in warmer temperatures. The study investigated the impact of high temperatures on these two species of catfish fed with plant-based diets supplemented with alternative animal protein sources. Results demonstrated reduced survival and growth metrics at high temperatures, with diet and temperature affecting digestibility coefficients, immune responses, and gene expression. Histological analysis also showed alterations in connective tissue structures in the gut of channel catfish at high temperatures. In response to the increasing need of sustainable and resilient aquaculture systems, these studies collectively provide insights into optimizing warm water aquaculture through strategic dietary supplementation and temperature management to enhance the growth, disease resistance and microbiome composition. These findings will further support the development of innovative aquaculture practices that will be capable of meeting the growing demands under changing environmental conditions.