Differences in energy utilization efficiency of digested protein, fat and carbohydrates in snakehead (Channa striata)
Phan, L.T.T. | Masagounder, K. | Mas-Muñoz, J. | Schrama, J.W.
This study aimed to assess if the relationship between digestible energy (DE) intake and energy retention (RE) is dependent on dietary macronutrient composition; and to quantify the energy utilization efficiency of digested protein (dCP), fat (dFat) and carbohydrates (dCarb) for growth in snakehead (Channa striata). This was achieved by conducting a 42-day feeding trial on snakehead (29.1 g) with a 4 × 2 factorial design. Nutrient digestibility, nitrogen and energy balances were measured. Four diets were formulated, which had contrasting levels of protein, fat and carbohydrates. Each diet was tested at 2 feeding levels, in order to estimate within each feeding level the relationship between DE and RE. Snakehead (a carnivore) is well able to digest starch. Starch digestibility ranged from 93% to 99.5%. The linear relationship between RE and DE intake was affected by diet. Diets with a high Carb content had a lower slope (0.45 versus 0.53 to 0.56), which indicates that DE is less efficiently used for RE. Multiple regression of RE as a function of dCP, dFat and dCarb (in g.kg⁻⁰.⁸.d⁻¹) intake was also applied to estimate the energy utilization efficiency of each digestible macronutrient. A linear relationship was found between RE and dCP, dFat and dCarb. Snakehead are a lean fish, which we observed prioritise digestible protein intake for protein gain. The estimated energy efficiencies of dCP, dFat and dCarb (respectively, kNE;dCP, kNE;dFₐₜ, and kNE;dCₐᵣb) for energy retention were 53, 79 and 5%, respectively. Snakehead can digest starch at the high level but cannot metabolise digested starch for growth efficiently.
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