Protein Ratio

Protein ratio, in feed formulation, is the proportion of crude protein in a diet expressed as a percentage of dry matter, typically ranging from 35–55% in aquafeeds: around 55% for marine carnivores such as sea bass and eel, 45–50% for salmonids, 40–45% for tilapia, and 35–40% for shrimp. Protein is the most expensive macro-ingredient, so the ratio is set to the minimum that meets the species' requirement for growth at a given life stage, then balanced by digestible energy to hit a target protein-to-energy ratio (about 22–26 g digestible protein per MJ in carnivorous fish). Feeding protein above requirement wastes nitrogen: surplus amino acids are deaminated and excreted as ammonia, directly raising the water's TAN load and pressuring biofilters in RAS. Conversely, protein below requirement reduces growth and FCR. For the feed producer, the protein ratio drives cost, fish meal and fish oil inclusion, and the need for crystalline amino acid supplementation (lysine, methionine) to balance the profile. The farmer reads it together with FCR and ammonia trends: a rising ammonia level on a high-protein diet signals the system, not the fish, is the constraint.