Aquaculture popularly called fish farming in Nigeria involves the breeding, rearing, and harvesting of fish or other aquatic animals and plants in controlled environments. For the reason of the high protein content of fish and the special flavour, fish farming has gained in popularity in Nigeria in particular and across the globe in general. As a fish farmer, I have always been concerned about the increasing number of challenges facing this agricultural sub-sector. One identified challenge is the risk experts say the use of antibiotics in fish farming poses to health, and as such I pay close attention to new researches in this area. One study that caught my interest was published in the Journal of Aquatic Animal Health.
Incidentally, the study involved a Nigerian, Olumide Samuel Olowe, who, while he was at the Pukyong National University, Busan, Korea led a team of other international researchers in establishing the effects of using synbiotics to improve growth and health of fish, comparing the results to those raised with antibiotics. Synbiotics are a combination of probotics and prebiotics which offer health benefits in a synergised way. They are found in foods, supplements, or as part of dietary regimen. Synbiotics enhance gut health as they improve the survival and activity of beneficial bacterial in the digestive system.
In recent years it has been a matter of concern among industry players the excessive reliance on antibiotics which, as I have come to understand, is bad for the environment, fishes themselves and for humans. The human angle is most important to me because, increasingly, health experts warn about the effects of antibiotics in the foods that humans consume. Different workshops that I have attended regarding fish farming indicate that consuming fish treated with excessive antibiotics can lead to allergic reactions as well as have some carcinogenic effects. The increasing reliance or overuse of antibiotics contributes to antibiotic resistance in bacteria, making it harder to treat human infection. This is a matter that food and health experts should pay serious attention, particularly in Nigeria where the National Agency for Food Drug Administration and Control continues to warn the public of the health effects of the use of certain chemicals in how some food items are produced, stored, or ripened.
The following information provides relevant backdrop to Olowe’s study. It is a known fact that the world oceans are under pressure from overfishing, and that waters close to shores as well as inland waters are over-exploited. As a result there have been intensive and high-density fish farming practices to ensure high yields and profits. Consequences of these include increased fish diseases and mortalities. This situation has led to the use of antibiotics to prevent as well as treat such diseases. When this is excessive antibiotics residues in fish pose potential human health risks due to their accumulation in humans through consumption. As in all other countries there are guidelines for use of antibiotics in fish farming in Nigeria. However, lack of adequate education on the subject among industry players as well as the improper sale and overuse of antibiotics to reduce loses and maximize profits remain a challenge.
In addition to this is the fact that antibiotics contained in fish have been found in wastewater from agriculture areas. This can remain for an extended period and is spread far and wide through water systems. Moreover, some antibiotics deployed in fish farming are similar to those used in humans; these include tetracyclines, macrolides and rifampin. As researchers have discovered, exposure to these antibiotics over a long period can reduce their effects in treating infectious diseases in humans. The foregoing and many more have therefore raised interest in investigations targeted at knowing the effects of the occurrence of antibiotics in fish farming as well as finding solutions to them. From my standpoint as an operator, this is where the study by Olowe and his colleagues has its significance.
The study’s focus of using synbiotics to improve growth and health of fish is interesting because it is an acknowledgement of much of the stated challenges associated with fish farming, especially the need to curb the unintended effects of antibiotics. For instance, Olowe’s study notes that for decades fish farmers have relied heavily on antibiotics to combat diseases in their animals. While effective in the short term, this widespread practice has sparked growing concern among environmentalists, and public health advocates. Overuse of antibiotics in fish farming has led to residual antibiotics entering the food chain and aquatic ecosystems, with potential risks for human health and marine biodiversity. As Olowe and his colleagues further note, some bacterial strains affecting fish, such as Edwardsiella tarda, have already shown resistance to multiple antibiotics, facilitated by transferable R-plasmids which are self-replicating DNA molecules that can be transferred between bacteria. This, in simple terms, is a process of genetic exchange that carries genes which confer resistance to multiple antibiotics.
This growing resistance does not only diminish treatment effectiveness but also threatens the sustainability of fish farming globally. In light of these challenges, the researchers are seeking sustainable alternatives that can promote fish health and performance without relying on pharmaceuticals. One promising solution is the adoption of synbiotics which improve gut health, bolster immunity, and support growth of fish. In this particular study, Olowe and his colleagues demonstrated the potential of synbiotics to replace antibiotics in Japanese Eel aquaculture. The researchers focused on two symbiotic formulations which were added to commercial diets and tested against a control diet, as well as to another diet supplemented with a commonly used antibiotic oxytetracycline (OTC).
The results showed that fish fed with one of the two symbiotic formulations adopted by the researchers showed significantly higher weight gain, specific growth rate, and feed efficiency compared to those fed with the control or antibiotic diets. Fish that received the second of the researchers’ two symbiotic formulations also performed well, but their growth metrics were not significantly different from the control group. Beyond growth, the researchers found promising results in the immune function. Specifically, fish on the symbiotic formulation diets exhibited elevated levels of innate immune function facilitated by relevant enzymes that played crucial roles in defending the fish against pathogenic bacteria.
In order to put the symbiotic formulation diets to the ultimate test, Olowe and his colleagues conducted a pathogen test. After the outcome of the feeding trial, fish were injected with a well known pathogen in aquaculture. The fish on the symbiotic formulation diets had significantly higher survival rates (62% and 67%) than those on the control diet (14%). Their survival was even slightly better than that of the fish treated with oxytetracycline (52%). These findings suggest that synbiotics not only promote growth but also improve the immune system to resist disease, while achieving similar or superior outcomes compared to antibiotics without the associated risks. Synbiotics improve the gut health of fish by simultaneously introducing beneficial bacteria and providing them with food to thrive. This synergy helps, among others, to enhance nutrient absorption and modulate the fish’s immune response. Healthy gut condition means a healthier fish, and as Olowe and his colleagues note in their study, “This translates to better feed utilization, improved growth, and greater resilience to pathogens.”
While this study focuses on Japanese Eel, the researchers say the implications extend across the aquaculture and all animal industries. I think this is important because as fish farming intensifies to meet global food demands, finding sustainable health management tools becomes paramount. As the researchers further note, their study is not just focused on boosting yields, there is as well “the long-term sustainability of aquaculture, where productivity, fish welfare, and environmental responsibility go hand in hand.” From my perspective, this study reflects a broader shift in the industry: moving away from antibiotics towards functional feeds that support fish health through natural alternatives. Without a doubt, this approach aligns with growing consumer demand for cleaner, antibiotic-free seafood and meets the goals of many regulatory bodies seeking to reduce antimicrobial use in food production.
While Olowe, now undergoing graduate studies at Purdue University, USA, notes with his fellow researchers that the effectiveness of synbiotics can vary depending on the fish species, the dosage used, and the specific combination of ingredients, the results from the study provide strong evidence that synbiotics are a practical and environmentally sound alternative to antibiotics. I am of the view that as the aquaculture industry continues to expand, solutions like these will be essential towards ensuring healthier fish, safer food, and a more sustainable future for global seafood production. For this reason, I specifically urge the various levels of governments in Nigeria to pay attention to research outcomes such as this one for the purpose of improving the sustainability of the fish farming sub-sector, as well as the health of fish consumers.
Dimas, a fish farmer, writes in from Taraba State, Nigeria.
