2 minute read
SOMETHING FISHY
The ornamental fish trade is a thriving industry globally, however, production is often affected by diseases. Traditionally, disease prevention and control in aquatic systems has focused on chemical compounds and veterinary medicines such as antibiotics. These treatments often bring an imbalance to the microbial environment in which the aquatic animal lives, as well as its digestive tract. Nowadays, due to us becoming more health and environmentally conscious, considering the global issue of antibiotic resistance and antibiotic residues which could potentially affect humans, alternative treatments which are safer for the environment are taking preference. In recent years there has been an increasing use of probiotics in aquatic systems, largely in aquaculture for food production, however the use of probiotics in ornamental fish production is now becoming more important. The Bacillus, Enterococcus, Carnobacterium species, and the yeast, Saccharomyces cerevisiae species, amongst others, are often used in probiotics in aquatic systems.
So what are probiotics? We are more familiar with yoghurt being a source of probiotics for humans. These are a combination of live micro-organisms, such as bacteria and yeasts that are naturally found on the body, and which are beneficial to the host (animals or humans). Probiotics improve the microbial balance of the body, and in aquatic systems, can be used as a food additive added directly to the culture tank or mixed with the animal’s food. It is available in liquid or powder form.
There are many benefits of probiotics to aquatic animals and this article highlights key benefits. It is important to note that research on the use and effect of probiotics in aquatic animals is ongoing. Probiotics are known to benefit both fish and shellfish by improving the balance and activity of micro-organisms in the digestive tract, which increases nutrient absorption and availability. They are also known to stimulate appetite, improve immunity and disease resistance, reproduction, feed conversion, growth and development. Most health problems in fish are due to poor water quality, which often provides a favourable environment for pathogenic micro-organisms, such as Vibrio species for example, to thrive in, in marine systems. The use of probiotics in the water increases the population of beneficial micro-organisms, which compete with pathogenic (disease causing) organisms. They secrete antibacterial substances, known as bacteriocins and organic acids, which compete with pathogens, preventing their adhesion to the intestine. They also compete with pathogenic microorganisms for nutrients necessary for their survival. Probiotics improve water quality by decreasing ammonium, nitrite, nitrate and phosphate ions, which in high concentrations, are toxic to fish. Yeasts used in probiotics are a source of immune stimulants, but also serve as a growth promoter in various fish species.
Probiotics are also known to improve fish larval survival to adulthood, which is a period in development where there are usually high losses, in addition to increasing fish larval development, which was noted in a study of zebra fish. This is important because this can be applied to rearing rare ornamental fish species to adulthood. Zebra fish, interestingly, share many similar genes to humans, and are used to study the beneficial effect of probiotics in humans. Fish and other aquatic animals are always exposed to some sort of stressor in the aquatic environment, whether it is an aquaculture system or home pond. According to studies conducted, fish showed lower stress levels when treated with probiotics.
If you are interested in knowing more about the use of probiotics in aquatic systems, please contact me on @aquaglobalveterinaryconsulting.com
