Feed intake, growth, and protein utilisation by post-smolt Atlantic salmon (Salmo salar) in response to graded levels of fish protein hydrolysate in the diet

Summary

This study investigated how partial dietary replacement of fish meal (FM) by a novel fish protein hydrolysate (FPH) affected feed intake, growth, feed efficiency, nutrient retention, and nutrient digestibility by Atlantic salmon in the early seawater stage. FM was replaced by FPH in increments, producing four extruded diets containing 0%, 5%, 10%, and 15% FPH. Each diet was fed to quadruplicate groups of 163-g salmon maintained in 8.3 °C seawater. The experiment lasted 68 days, divided into three periods. The feed consumption was higher in groups fed 10% and 15% FPH than in those fed 0% FPH, with intermediate intake in groups fed 5% FPH. This was mirrored by the growth, and the groups fed 0%, 5%, 10%, and 15% FPH reached respective individual weights of 323, 350, 362, and 377 g. The retention of protein, which ranged from 48% to 53%, was higher in groups fed 5% and 15% FPH than in those fed 0% FPH. The protein retention was lowest in the groups fed 10% FPH. The retentions of individual amino acids largely mirrored the overall protein retention. The differences in apparent digestibility of protein and individual amino acids were slight, but generally highest when feeding 5% and 15% FPH, lowest when feeding 0% FPH, and intermediate when feeding 10% FPH. In conclusion, the tested FPH proved an efficient feeding stimulant in Atlantic salmon and was highly digestible and well utilised for growth.