The primary reason juvenile fish require feed with higher protein content than adult fish lies in their explosive growth phase during early life. Juvenile fish experience rapid development of muscles, bones, and organs, all of which heavily rely on amino acids from protein as "building materials," resulting in a substantially higher demand.
Additionally, their digestive systems are not yet fully developed, leading to lower efficiency in protein absorption and conversion, which necessitates greater intake to meet growth requirements. Furthermore, juvenile fish prioritize using protein for energy expenditure (rather than storing fat), whereas adult fish can utilize fats or carbohydrates for energy, thereby conserving protein. Inadequate protein intake in juvenile fish can lead to stunted growth and an increased rate of deformities.
Therefore, high-protein feed (40%–50%) is essential for the healthy development of juvenile koi.
