Ameliorating effects of natural herbal supplements against water-borne induced toxicity of heavy metals on Nile tilapia, (Oreochromis niloticus)

Abstract

The efficacy of herbal supplements in mitigating heavy metals (HMs) toxicity was investigated using a widely grown fish, the Nile tilapia (Oreochromis niloticus). The experiment was conducted over two phases: during the stress phase, the experimental fishes were exposed to sub-lethal concentrations of HMs, including lead, cadmium, zinc, and copper for 15 days; following which during the feeding phase, herbal supplements were given for 70 days to ameliorate their effects. Seven groups were established: the control negative group (CON-ve), control positive group (CON+ve, without any treatment), and five groups with supplementation of 1% turmeric (TUR), cinnamon (CIN), ginger (GIN), garlic (GAR), and their mixture (MIX), respectively. A total of 315 fishes were distributed evenly in experimental tanks (15 fishes per tank, in triplicates). The results revealed that exposure to HMs led to significant (p < 0.05) alterations in all the tested parameters, i.e., liver damage and growth reduction. The herbal supplements, especially the MIX groups, ameliorated the harmful effects of HMs and restored fish growth, digestibility, carcass composition, and liver health. In conclusion, the study demonstrated that the herbal supplements were effective in reducing the HMs-linked toxicity in Nile tilapia. Future studies pertaining to the mechanisms facilitated by the various herbal bioactive substances-linked tolerance to HMs in fishes are warranted.

Keywords: Growth; Heavy metal; Herbal supplement; Histopathology; Nile tilapia; Toxicity.

Fig. 1

The FCR and SGR% of O. niloticus fed natural herbal supplemented diets.

Fig. 2

Graphical representation of body composition in terms of crude protein (%) and crude fat (%).

Fig. 3

The apparent nutrient digestibility (%) of O. niloticus fed with natural herbal supplemented diets.

Fig. 4

Representative photomicrographs of liver tissues from the different groups of O. niloticus fed with heavy metals (HMs) mixture and natural herbal supplements: (a) Control (CON)-ve group: Normal liver histology with round nuclei (N) and intact sinusoids (S). (b) CON+ve group: Severe alterations, including necrosis (NC), oedema (OE), hepatocellular vacuolation (HPV), pyknosis (PC), and sinusoid dilation (SD). (c) Turmeric (TUR)-treated group: Improved liver histology with reduced NC. (d) Cinnamon (CIN)-treated group: Restored normal liver architecture, with round N, recovered central vein damage (CV) and stopped sinusoid dilation (SD). (e) Ginger (GIN)-treated group: Normalized liver histology, with stopped SD and recovering round N. (f) Garlic (GAR)-treated group: Improved liver histology, with stopped SD. (g) Mixed herbal supplement (MIX)-treated group: Enhanced liver recovery, with reduced NC and normalized round N of hepatocytes (H).