Phyllanthus niruri supplemented diet as a modulator of stress and immune responses in Nile tilapia, Oreochromis niloticus, reared in inland recirculating and aquaponics systems

Md Ibrahim, Purdue University

Abstract

Fish and other aquatic products have been used as important protein sources to meet the protein demand of world’s exponentially growing human population. These aquatic products mainly come from natural and aquaculture sources. But due to the decline in natural resources, the popularity of growing aquatic animals in a controlled aquaculture environment is increasing. As aquaculture follows intensive farming methods, it encounters some problems. One of the problems comes from using drugs in culture media to control or prevent diseases caused by some stressful aquaculture activities such as overcrowding, handling, poor nutrition, and changes in environmental parameters. Use of nutraceuticals as fish feed additives can stimulate immune system and prevent disease infection in an ecofriendly way, and hence, reduction in the drug use. Phyllanthus niruri, a tropical plant under Euphorbiaceae family, has the properties of nutraceutical which is being used by humans as anti-diabetic agent (reducing blood sugar), kidney and gall bladder stone breaker, anti-viral and bactericidal agent etc. As it reduces the blood sugar level, we hypothesized it would work as s stress reliever for fish if it is used as additive in fish diet. To test this hypothesis, we reared Nile tilapia, a popular aquaculture species, in inland recirculating system and aquaponics system. We wanted to compare the effects of P. niruri on tilapia fish growing in these two systems, if there are stresses present in each system. Fish were reared for three months at low (5 g/L) and high (30 g/L) densities and sampled at week 0, 4, 8, and 12 (n=6) to measure the physiological and immunological responses. Findings indicate no significant differences in plasma cortisol concentrations among the experimental groups, but blood glucose concentrations were higher in high-density groups in both systems. Supplemented diet groups had lower level of blood glucose than control feed groups, but the differences were not statistically significant. Other physiological parameters such as packed cell volume and plasma proteins did not reveal a general trend in both systems. Similar results were found for immunological parameters such as phagocytic capacity, respiratory burst activity, spleen somatic index, and lysozyme activity. In comparison between two systems, in aquaponics, packed cell volumes (PCV) were significantly (p<0.05) lower in supplemented diet groups than control feed groups when all sampling stages were analyzed together. No significant differences were found in recirculating systems for PCV in the same analysis. Other parameters did not have conclusively contrasting features. In terms of yield, weight gain of fish was higher in aquaponics system than recirculation system. Besides this, an extra plant production of three plant species was obtained from aquaponics system, and aquaponics had less ammonia toxicity than the recirculating system. Overall, findings from this research could not establish the appropriate stress response in both systems, and hence, the role of P. niruri as a stress reliever was not established. As tilapia is hardy fish, and cope up with stressors easily, further study needs to be done on this species or other fish species using same and other type of stressors.

Degree

M.S.

Advisors

Mustafa, Purdue University.

Subject Area

Biology

COinS