Effect of dietary carbohydrate and fat supplementation on the yield and chemical composition of fillet and the location of fat deposition in striped catfish (Pangasius hypophthalmus), African catfish (Clarias gariepinus) and snakehead (Channa striata)

This study compared three different fish species, striped catfish (Pangasius hypophthalmus), African catfish (Clarias gariepinus) and snakehead (Channa striata), regarding the effect of dietary macronutrient composition on: 1. the fillet yield and the fillet chemical composition; 2. the location of fat deposition within the body (fillet, liver, viscera or rest fraction). The selected species were studied for the development of net energy formulas, in three different studies. The design of these studies and especially the diet formulation were similar. Diets were formulated according to a 2 × 2 factorial design: with or without extra carbohydrates supplementation; and with or without extra fat supplementation. Fillet yield of striped catfish (P. hypophthalmus), African catfish (C. gariepinus) and snakehead (C. striata) was not affected by the dietary macronutrient composition. Fillet fat and protein contents were changed by the dietary macronutrient composition. In all compartments (liver, viscera, fillet and the rest fraction), both dietary fat and dietary carbohydrates levels increased the fat content. The response to dietary carbohydrates in snakehead, a lowering of fillet fat content, is opposite to the response in both catfish species. The distribution of the total amount of body fat over the different compartments, was not influenced by dietary carbohydrates level, but did depend on dietary fat level. Dietary fat supplementation led to relatively more fat in viscera and fillet but less fat was stored in the rest fraction. In striped catfish (P. hypophthalmus), African catfish (C. gariepinus) and snakehead (C. striata), most of the body fat is stored in the rest fraction (head, skin, subcutaneous fat, scales, bones and air bladders)