Sherif, A.H.1; Soliman, H.A.2 and Heba, H. Elgharib2

1 Dep. Fish diseases 2 Dep. Pathology, Kafr El-Sheikh provincial lab, Animal Health Research Institute (AHRI), Agriculture Research Center (ARC).

Received 8/ 9/ 2013

Accepted 15/ 10/ 2013


In this study, the evaluation of the negative impacts of sub-lethal concentration of un-ionized ammonia (NH3) on the health status of Oreochromis niloticus (O. niloticus) had been conducted. Ninety O. niloticus fish were exposed to three levels of NH3 (0.05, 0.1 and 0.5 mg.l-1) for 14 days then NH3 were adjusted to the lowest level 0.05 mg.l-1 for another 14 days. O. niloticus was challenged against A. hydrophila at the end of the experimental period (28 days) to record mortality rates.

Results recorded that resistance of O. niloticus was declined and high mortality rates against challenge A. hydrophila especially in group exposed to high concentration of NH3 (0.5 mg.l-1). Decrease of RBCs, HB, PCV, MCV, MCH, MCHC, WBCs with increase in glucose and cortisol were observed along with increasing NH3 level. The phagocytic index and phagocytic assay showed lower values with 0.5 mg.l-1 group, while liver enzyme, urea and creatinine showed significant increase. The previous parameters came back to normal values after stopping exposure to high concentration of NH3.
The histopathological examination revealed degeneration and necrosis in gills, liver and muscles. It could be concluded that clinical findings and histopathological lesion were varied according to change in the NH3 concentrations. Also, it was found that the lesions were aggravated with the increasing of NH3 concentrations. Immune suppression caused by stress of NH3 lasted for a period of time after lowering the NH3 concentration during which O. niloticus were susceptible to bacterial diseases.

Key word: un-ionized ammonia, Oreochromis niloticus, survival rate, cortisol, liver enzyme and A. hydrophila.