Among the alternative ingredients, p lant proteins (PP) are the most commonly used in aquafeed . However, PP contain anti-nutritional factors and imbalanced nutrient composition which a dversely affect the performance, health, and fillet quality of fish. The f eed additives can improve the growth and health of fish. The goal of the study was to assess the impact of the PP diets (~30% soy) supplemented with the additive mixture (A) on the growth and fillet quality of rainbow trout and establish a feeding protocol based on muscle fibre recruitment pattern to maximize PP utilization.
In a seven-month feeding trial, 2,000 fish (2.22 g) were divided into four groups with 5 replicates (100 fish/tank), fed isonitrogenous (42% crude protein) and isolipidic (20% lipid) diets: control (30% FM), plant protein (PP) , PP+A1 (krill meal, taurine, and organic selenium), and PP+A2 (proline, hydroxyproline, and vitamin C).
Results indicate that FM, PP+A1, and PP+A2 groups exhibited significantly higher (p < 0.05) weight gain compared to the PP group. Additionally, the additive mixtures (PP+A1 and PP+A2) maintained fillet quality, showing significantly increased (p < 0.05) hardness and chewiness compared to the FM and PP groups during 90 days of storage at -20oC. Muscle histology revealed four growth phases based on muscle fiber recruitment (Figure 1 and 2) : hyperplasia (2.2 - 15 g), hypertrophy (15 - 50 g), hyperplasia (50 - 150 g), and hypertrophy (150 - 350 g). Conclusively, supplementing additive mixture in PP-diet can mitigate their negative effects in rainbow trout. Based on identified muscle recruitment pattern in growth phases offer valuable insights for precision nutrition in future feeding trials.