Effect of Different Levels of Dietary Carbohydrate on the Growth Performance and Nutrient Utilization of Blue Gourami, Trichogaster trichopterus

Abstract

This study evaluated the effects of graded dietary carbohydrate (CHO) levels on the growth performance and nutrient utilisation of blue gourami (Trichogaster trichopterus) fingerlings. Juvenile fish with an initial average weight of 1.76 ± 0.01 g were randomly stocked at a density of 10 fish per tank in triplicate in indoor fibre-reinforced tanks (500 L capacity) filled with 100 L of water. Six semipurified diets were formulated to contain graded CHO levels (T1-20%, T2-25%, T3-30%, T4-35%, T5- 40%, and T6-45%) while maintaining constant levels of crude protein (35%) and lipid (8%). The feeding trial was conducted over a period of 60 days. At the conclusion of the trial, fish fed the diet containing 40% CHO exhibited significantly (p < 0.05) superior growth performance, as evidenced by higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER), and protein retention efficiency (PRE), along with a significantly lower feed conversion ratio (FCR), compared to other dietary treatments. Whole-body proximate composition analysis revealed significant (p < 0.05) differences among treatments. The highest crude protein content (16.40%) was recorded in fish fed the 20% CHO diet (T1), whereas the lowest (15.31%) was observed in fish receiving the 45% CHO diet (T6). Conversely, total lipid content was highest in the T6 group (5.29%) and lowest in T1 (4.27%). Ash content peaked in T1 (3.22%) and was lowest in T6 (2.84%). Whole-body carbohydrate content increased with dietary CHO levels, with the highest value recorded in T6 (1.55%) and the lowest in T1 (1.12%). These findings suggest that a diet containing 40% carbohydrates is adequate to support optimal growth and nutrient utilisation in blue gourami, T. trichopterus fingerlings.