Effects of different rations on production performance, spinal anomalies, and composition of Chinook salmon (Oncorhynchus tshawytscha) at different life stages

Abstract

The effect of feeding restricted rations was investigated in two different size classes of Chinook (King) salmon (Oncorhynchus tshawytscha). Smaller individuals (725 g initial mean weight) were fed with 100% (satiation, SR1), 90.4% (SR2), or 81.6% (SR3) feed rations for 64 days, while larger individuals (1689 g initial mean weight) were fed with 100% (LR1), 82.6% (LR2), or 76.1% (LR3) feed rations for 119 days. The growth performance was evaluated for both size classes, and for the larger individuals, the analysis also included spinal curvature incidence (lordosis–kyphosis–scoliosis (LKS)), whole-body and fillet proximate composition, and fatty acid profiles. In both size classes, the final weight, weight gain, specific growth rate (SGR), and condition factor (CF) were significantly higher in individuals fed to satiation (SR1 and LR1) compared to individuals fed restricted rations (SR2 and LR2, SR3 and LR3). However, no significant differences in FCR were observed among the different treatments. Although the incidence of spinal curvature and vertebral body anomalies (i.e., compressions, fusions, vertical shifts) in the larger individuals were higher for the groups fed to satiation (LR1) compared to the groups fed restricted rations (LR2 and LR3), only the differences in vertebral anomalies were statistically significant. No significant differences were observed in whole-body and fillet proximate composition, while several significant differences were observed in the fatty acid profiles (whole-body and fillet) of larger individuals fed different rations. Monounsaturated fatty acids (MUFA), especially oleic acid (OA, 18:1n-9), and n-6 polyunsaturated fatty acids (n-6 PUFA), especially linoleic acid (LA, 18:2n-6) levels, were higher in fish fed to satiation. In contrast, saturated (SFA), primarily palmitic acid (PA, 16:0), and n-3 polyunsaturated fatty acids (n-3 PUFA), primarily eicosapentaenoic acid (EPA, 20:5n-3), and docosahexaenoic acid (DHA, 22:6n-3), were lower in groups fed the higher rations. Despite the overall improved growth performance of the groups fed to satiation, our results suggest that feeding Chinook salmon restricted rations has the potential to decrease the incidence of spinal anomalies, particularly vertebral body anomalies, and improve product quality (based on n-3 PUFA levels), without compromising FCR.