Background. Dietary carbohydrate use is a priority in aquaculture because of its low cost and high availability, especially for herbivorous and omnivorous fish. Gelatinization is a process that improves carbohydrate use. However, excess dietary carbohydrate may cause metabolic stress and cellular changes as fish inherently use low carbohydrate. The aim of this study was to determine the effects of three sources of gelatinized carbohydrate (GC) on haematology and hepatic structure of Catla catla fingerlings. Materials and methods. Six isocaloric (17.1-17.5 kJ*g–1) semi-purified diets were prepared from rice, corn, or tapioca, each at 40 or 50% GC. Crude protein (CP) level was fixed at 35 and 25% for the low GC (40%) and high GC (50%) levels, respectively. Ninety Catla catla fingerlings were distributed in 6 treatments, each with three replicates, for a 60-day feeding trial. At termination, blood haemoglobin, RBC, WBC, and liver histology were studied. Results. Significant differences (P < 0.01) in haemoglobin, RBC, and WBC were observed among the different carbohydrate-fed groups at 40% GC level. With increased dietary GC level, hepatocyte hypertrophy and vacuolation was intensified. Maximum hypertrophy was noticed in the fish fed tapioca at 50% GC, with extensive cytoplasmic vacuolation. No mortality was found in any group at any GC level. Conclusion. No mortality of Catla catla fingerlings was observed due to feeding of high GC levels from corn, rice, or tapioca. However, hepatocyte hypertrophy was observed. Long-term feeding beyond 60 days may cause adverse hepatic cellular changes, but needs further research.

corn, rice, tapioca, gelatinization, haematology, histology, hypertrophy, Catla catla, fish