What is the most appropriate energy-to-protein ratio for fish feed?

Since the first requirement of fish in taking in nutrients is to meet their energy needs, from the perspective of fish nutrition, energy is the foundation of fish feed quality. The energy in feed is the sum of the energy contained in the three major nutrients in the feed - protein, fat, and carbohydrates. As a nutrient, protein is not only a major energy-supplying substance, but also has extremely important physiological functions, and these physiological functions cannot be replaced by fat and carbohydrates, and fish have a particularly high demand for protein, so protein is the first nutrient to consider in feed. Consequently, fish nutrition experts raised the question of the relationship between energy and protein: exactly how much energy and how much protein should be contained in feed to be reasonable. The energy-to-protein ratio (abbreviated as E/P ratio) is an indicator for measuring this; it refers to the ratio of the total energy (kilojoules) contained per kilogram of feed to crude protein (grams).

The energy-to-protein ratio has important practical significance in fish nutrition. An appropriate energy-to-protein ratio in feed is beneficial both to the utilization of energy and to the utilization of protein, thereby improving feed utilization efficiency. Therefore, studying the appropriate energy-to-protein ratio in fish feed is extremely beneficial for improving feed utilization efficiency and improving aquaculture results. For example: the optimal energy-to-protein ratio for grass carp feed is 36.8-57.7 at the juvenile stage, the optimal energy-to-protein ratio for black carp feed is 38.1, and the optimal energy-to-protein ratio for blunt snout bream feed is 36.