Goose fat, a promising nutrient for fish feeding, activates antioxidant enzymes in rainbow trout, Oncorhynchus mykiss

• Four iso-nitrogenous and iso-lipidic casein–gelatin based experimental diets with varying dietary sources were formulated.
• Activities of antioxidant enzymes were analyzed upon different dietary lipids.
• All enzyme activities were elevated upon GF diet.
• Goose fat is a promising candidate to be used in fish feeding.

The objective of this experiment was to test effects of different dietary lipids in rainbow trout feeding on the activity and expression of antioxidant enzymes, superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione S-transferase (GST). Four iso-nitrogenous and iso-lipidic casein–gelatin based experimental diets were formulated. The sources of dietary lipids were cod liver oil (CO, rich in polyunsaturated fatty acids), goose fat (GF, rich in saturated fatty acids and monounsaturated fatty acids), soybean oil (SO, rich in linoleic acid), and a blend of CO, GF and SO. Dietary treatments had no significant effect on growth performance and survival was not affected. SOD, GPx and GST enzymes had the maximum activity in GF diet. However qPCR data showed that SOD and GPx mRNA levels were minimum in GF group. Overall data showed that rainbow trout liver enzymes were activated upon GF diet probably activating the enzyme structure itself without stimulating gene expression.