Submitted to: Fish Physiology and Biochemistry Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/30/2003
Publication Date: 3/30/2002
Citation: Lochmann, R.T., Davis Jr, K.B., Simco, B.H. 2002. Cortisol responses of golden shiner (notemigonus crysoleucas) fed diets differing in lipid content. Fish Physiology and Biochemistry Journal. 27:29-34. Interpretive Summary: The golden shiner is the predominant fish species raised for bait for recreational fishing in the US. Baitfish are marketed as live products, and they undergo frequent handling during production and transport to retail outlets. Nutritional enhancement of stress resistance is more important for baitfish than diets which maximize growth. The plasma cortisol response to a low-water stress was compared among groups of fish fed diets differing in amounts and types of dietary lipid. In experiment 1, golden shiners were fed low or high dietary lipid derived from either menhaden or poultry lipid for 4 weeks before subjecting the fish to the stress test. The pattern of the cortisol response was similar to that seen in other species, however there was no difference in fish fed the different diets. In experiment 2 fish were fed a 10% lipid diet derived from cottonseed oil (CSO), cod liver oil (CLO), soybean oil (SBO), or a combination of soybean and cod liver oils. Fish fed the diet with equal amounts of soybean oil and cod liver oil had lower initial cortisol levels and higher cortisol levels 2 h after removal of the stress when compared to fish fed the other diets. The main differences between the diets were the relative amounts and types of fatty acids of the n-3 and n-6 families. Diet lipid composition may be able to affect the cortisol stress response under some conditions.
Technical Abstract: The purpose of this study was to characterize the plasma cortisol response in golden shiners under crowding stress, and to determine whether dietary lipid composition affects the cortisol response. In experiment 1, triplicate groups of golden shiners were fed diets with 4 or 13% menhaden fish oil, or 4 or 13% poultry fat for 4 weeks before the crowding stress. In experiment 2, fish were fed diets with 10% lipid from cottonseed oil (CSO), cod liver oil (CLO), soybean oil (SBO), or soybean+cod liver oil for 6 weeks before the stress test. Serum cortisol was measured initially, two hours after the stressor was applied, and two hours after the stressor was removed. Cortisol responses were not significantly different among fish fed different diets in experiment 1. The overall pattern of the response was similar to that seen in other warmwater fishes. However, the magnitude of the cortisol response 2 h after application of the stress and after 2 h recovery time appeared to be greater in golden shiners than in many other species. In experiment 2, initial and recovery cortisol levels were affected by diet. Fish fed a diet with equal amounts of SBO and CLO had reduced initial cortisol relative to fish fed the other diets. Two hours post stress, fish fed the SBO+CLO diet had not recovered and had significantly higher cortisol than fish fed diets with either SBO or CLO alone. The main differences between the diets were the relative amounts and types of fatty acids of the n-3 and n-6 families.