Choice preference of diets with different protein levels depending on water temperature in Nile tilapia

This study tested a choice feeding model for Nile tilapia that allowed the selection of a higher or lower protein content in the diet depending on water temperature. Nile tilapia were reared in twelve 200-L tanks for 63 days with 12 fish (body weight 38 g/fish at start) per tank. Two temperatures (22 or 30 degrees C) and two color combinations (yellow and red each) for a two-component diet containing 30% (low) and a 38% (high) crude protein content based on dry matter were used. High water temperature (30 vs. 22 degrees C) resulted in a significantly higher feed rate (1.93 +/- 0.123 and 1.26 +/- 0.100%, respectively), body weight gain (39.3 +/- 4.29 and 4.75 +/- 0.66 g, respectively), final body weight (70.3 +/- 9.31 and 43.0 +/- 7.49 g, respectively), and feed efficiency (55.4 +/- 6.09 and 14.6 +/- 2.86%, respectively), as well as protein efficiency ratio (1.687 +/- 0.186 and 0.450 +/- 0.087, respectively), regardless of color codes. No significant differences of color codes on growth parameters, body composition, and fatty acid profile were seen. Higher water temperature (30 vs. 22 degrees C) only had an effect on percentage-specific fatty acids of total fatty acids of the whole body (biggest difference: C16:0, 20.5 +/- 1.00 and 17.4 +/- 1.11%, respectively). Therefore, water temperature clearly influences growth and fatty acid composition of the body.