Effect of Dietary Carbohydrate Forms on Zootechnical Parameters and Liver Histology of the Malaysian Mahseer, Tor tambroides

Abstract

Carbohydrates play a crucial role in the natural diet of freshwater fish by serving as a readily available energy source that support metabolic functions and spares protein for growth and tissue repair. Their utilization efficiency varies among species, influenced by digestive physiology, feeding habits, and the complexity of carbohydrate types present in the natural environment. Despite growing interest in carbohydrate utilization in tropical freshwater species, there is limited information on the ability of Malaysian mahseer T. tambroides to utilize simple sugars compared to complex polysaccharides. This study evaluates two simple forms of carbohydrates in the diets of T. tambroides against starch. In an eight-week feeding trial, soluble polysaccharide (starch) was incorporated at 234.4 g kg-1 dry matter (control diet), whereas monosaccharide (glucose) and disaccharide (sucrose) were incorporated to completely replace the starch in the diet for the treatment groups. Fish responses to these diets in terms of growth performance, feed efficiency, body composition, and liver histology were assessed. Fish fed simple sugars exhibited significantly lower protein, lipid, and energy retention values (PRV, LRV, ERV); approximately half or less of those observed in the starch-fed group. Conversely, carbohydrate retention (CRV) was notably higher in these groups, indicating an inefficient utilization of dietary glucose and sucrose by T. tambroides. Nonetheless, observation of liver histology did not reveal any deleterious effects of the dietary treatments. This study concludes that complex polysaccharides are better utilized than simple sugars to fulfill the dietary exogenous carbohydrate needs of T. tambroides.