Is fish gut microflora influenced by inulin?

Sustainability in aquafeeds is the need of the hour, the successful use of inulin via its unique effects on intestinal health, can contribute to a more sustainable aquafeed production with improved feed efficiency and better health status of the fish.

Aquaculture is one of the most swiftly-widening industries in the world and has been playing and important role in the economic development front on account of its contribution to food and nutritional security, national income, employment opportunities as well as generating livelihood options. The healthy functioning of an aquaculture system is sustained by addition of some additives in the feed, that selectively stimulate the growth and metabolism of health promoting bacteria in the gut by inulin, which is a prebiotic.

Inulin was discovered during 1804 by German scientist, Valentine Rose. He found a “peculiar substance” from Inula helenium roots by boiling water extraction. It is most often extracted from chicory roots which is composed of 68% inulin.

WHAT IS INULIN?
Inulin is a polydisperse carbohydrate consisting mainly of β (2→1) fructosyl-fructose links, generally referred to as fructan, and typically have a terminal glucose. Inulin is named in the following manner, where n is the number of fructose residues and py is the abbreviation of pyranosyl. In general plant inulin contains between 2 and 70 fructose unit or sometimes as high as 200.

INULIN – NON-DIGESTIBLE CARBOHYDRATE
Inulin is a non-digestible carbohydrate; the fibre cannot be digested by the digestive enzymes in the gastrointestinal system but has a distinctive action in the gut by enhancing the growth of gastro intestinal flora. The frothing of inulin in the colon enhances the short chain fatty acid production which stimulates the villi to grow and improve the absorption of nutrients. The latter has positive influence on zoo-technical performances of fish through a high specific growth rate and lower feed conversion ratio (FCR) and also increase the general disease resistance of fish. Prebiotics are easy to incorporate in the ration, non-carcinogenic, low calorific value, stimulate beneficial gut microbes and no residual effect.

UNDERSTANDING PREBIOTICS AND FIBER
Both prebiotics and fiber are dietary tools to promote health.

Prebiotic
Prebiotic is a food for beneficial members of resident microbial community- fishes generally cannot digest prebiotics, but certain beneficial microbes in the fish intestine paves the way for the happening.

Fiber
Fibers are non-digestible plant derived carbohydrates comprising at least 3 units of individual sugars.

DO FISHES NEED BOTH PREBIOTICS AND FIBER?
Most of the fishes do not get enough fiber in their diets. The supplementation of fiber-rich food and prebiotic- containing food will certainly promote the gut health and benefit the gut microbiota. They increase the mineral absorption. The pre-biotics are being fed to the probiotics, strengthening their effect. Thus, taking the two in combination can help make your probiotics more effective.

INULIN: AN ALTERNATIVE TO ANTIBIOTICS
Addition of antibiotics in human was a threatening factor to public health, because of the development of acquired antimicrobial resistance in fish pathogens and other aquatic bacteria. Antibiotics added in food producing animal also cause major effects in human health.

Inulin can offer an alternative to the traditional use of antibiotics in aquaculture by activating the innate immune system. Research on the effect of inulin in seabream, sturgeon and tilapia showed a clear effect on important immunological parameters such as increased immunoglobulin level, a higher lysozyme activity and enhanced white blood cell levels. These parameters cause an increase of the general disease resistance of fish.

PROS OF INULIN IN FARMED FISHES:
• It improves growth rate and survival of the fishes.
• It removes excess mucus from the walls of the small intestine of the fish.
• It stimulates the reproduction of useful microflora in the intestine of the fishes.
• Improves microbiota of the gastro intestinal mucosa is achieved by inulin supplementation.
• Maintains an optimal pH in the intestine of the fish.
• Improves the working process of digestive system.
• Better development of the tract is obtained using inulin
• Reduces susceptibility to disease
• The inulin positively altered haemato-immunological parameters of the fishes.

CONCLUSION
Sustainability in aquafeeds is the need of the hour, the successful use of inulin via its unique effects on intestinal health, can contribute to a more sustainable aquafeed production with improved feed efficiency and better health status of the fish.

FUTURE PROSPECTS
The studies should be conducted to make probiotics viable on an industrial scale to improve nutritional strategies for the efficient production of healthy aquatic animals.

About M. Joshna
M. Joshna is currently pursuing her doctor of philosophy in aquaculture at Dr. M.G.R. Fisheries College and Research Institute, Ponneri. She has dissertated her master degree thesis on “Inulin in GIFT species.” Sticking to the quote “To attain knowledge, add things everyday” she has been attending various international and national seminars to nurture the knowledge of fisheries. She has published several reviewed articles.

About Kamalii Ahilan
Kamalii Ahilan, gravitational pull towards fisheries since childhood has paved the way to pursue her masters in aquaculture at Dr.M.G.R. Fisheries College and Research Institute, Ponneri. Being a tree-hugger, she certainly wanted the fisheries to be in line with sustainability. Her current works are focussed on the use of insect meal (black soldier fly larvae) to replace the fish meal in aquaculture. Being moved by the quote “Awareness is the greatest agent of change”, she has conducted several seminars and spoke up on sustainability to make the people aware of the pertaining menace situation and the urge to combat back to normalcy. She has also published several reviewed and popular articles in the view of aquaculture.