DIFFERENT STARCH SOURCES IN EXTRUDED DIETS FOR THE MALAYSIAN MAHSEER (Tortambroides): EFFECTS ON GROWTH, FEED UTILISATION AND TISSUE HISTOLOGY

Abstract

Sago (Metroxylon sagu), cassava (Manihot esculenta) and taro (Colocasia esculenta) are potential sources of carbohydrate in lieu of corn starch because of they can easily be grown as crops in Malaysia. We investigated the effects of these starch sources on the growth, feed utilisation efficiency, body composition, and liver and intestine histology in Malaysian mahseer (Tor tambroides) (Bleeker, 1854) fingerlings for 10 weeks. Results showed that different starch sources had significant effects (P<0.05) on growth, feed utilisation efficiency and biometric indices. Moisture, lipid and gross energy composition of the fish carcass were also significantly different (P<0.05). Generally, fish fed with corn and taro starch produced better weight gain, length gain, specific growth rate and lower feed conversion rate values. However, fish fed with corn starch showed high conversion of carbohydrate to lipid compared with taro starch. In tissue histology, T. tambroides liver hepatocytes and intestine mucosal epithelial cells were susceptible to lipid vacuolisation in different degrees when starch was included in the diet. In conclusion, our study suggests that T. tambroides had limited capability in utilising starch from different sources. However, taro starch might be the best candidate for full/partial replacement of corn starch in T. tambroides extruded feed.