The objective of this research was to investigate a possible protective effect of Kai green algae (Cladophora and Microphora) as fish supplementary diet against lead-induced toxicity in catfish. Catfish were fed with 0%, 10% and 15% of Kai supplementary diets for 3 months, each of which had three replicates of 50 fish/tank. Haematological [Red blood cell (RBC) and white blood cell (WBC) counts, as well as packed cell volume (PCV)l, lysozyme, and antioxidant enzymes (superoxide dimustase, catalase, and glutathione S-transferase) of fish were examined after 30, 60 and 90 days of feeding. Catfish were then divided into groups (10 fish each) and subjected to heavy metal treatment. The fish were exposed to 0 of Pb (negative control), 1/2, LC50 (0.3 ppm), and the concentration of Pb that found in Mae Kuang River (0.004x10(-6)). After this exposure period catfish (n = 3 per tank) were collected three times (namely Days 7, 15, and 30). The results demonstrate that fish fed with Kai showed increased levels of superoxide dimutase (SOD), catalase, and PCV (P < 0.05) compared with the control group. RBC, glutathione S-transferase (GST), and serum lysozyme were not also significantly different. Catfish which received 15% Cladophora sp. supplementation showed the best record of white blood cell count and hematocrit. The counts of RBC, WBC, and the values of PCV were decreased in the Pb exposure group compared to control group. On the other hand, these values were slightly increased in the Cladophora sp. fed groups. Catfish fed a diet containing Cladophora sp. supplementation at the level of 15% had a higher lysozyme than those fed the control diet after Pb exposure. Moreover, a reduction in SOD activity was observed in catfish fed with diets containing Cladophora sp. These results suggest that Kai supplementation may be useful in prevention catfish from lead toxication.
