Stress response of tilapia, Oreochromis niloticus, when fed diets supplemented with sweet potato (I. Batatas) shoots and exposed to ammonia

Abstract

The present study investigated the hematology, survival and behavior of Oreochromis niloticus that received formulated diets (FD) with Ipomoea batatas shoots (IbS) as powder or extracts, when exposed to sub-lethal dose of ammonia. The study had four experimental treatments: a control treatment that received formulated diets (FD) only and three treatments that received FD with 5% I. batatas shoots powder (FD+PIbS), hot-water extract (FD+HWEIbS), and crude ethanol extracts (FD+CEEIbS). After 12 weeks of feeding, the fish were exposed for 21 d to a sub-lethal dose of ammonium chloride causing the stress response. During the exposure an increase in the leukocyte indices (white blood cells, WBC; neutrophils, NEU; lymphocytes, LYM; monocytes, MON) was observed in the fish that received FD only while the fish that received FD with I. batatas remained comparable. In contrast, the erythrocyte indices (red blood cells, RBC; hematocrit, HCT; hemoglobin, HGB) of the fish that received I. batatas were elevated and significantly different (P<0.05) from the control group. The platelet (PLT) count of the fish that got FD+HWEIbS was significantly higher than in the other treatments. In terms of survival rate, the fish that received FD+HWEIbS was top ranked. The swimming activity of the fish was reduced during the exposure, as a change in behavior. In conclusion, nutritional supplementation of I. batatas, particularly as hot-water extract, enhanced tilapia's resistance to physiological stress such as from ammonia exposure, as evidenced by its haematological profile and high survival.

Keywords

• sweet potato powder and extract
• ammonia toxicity
• tilapia hematology