Serum and hepatic lipid fractions and total protein status of laying hens supplemented with tarragon (Artemisia dracunculus L.) under different stocking densities

High stocking density can induce metabolic disturbances in laying hens, particularly in lipid metabolism. This study evaluated the effects of dietary tarragon (Artemisia dracunculus L.) supplementation on serum and hepatic total protein and lipid parameters in laying hens reared under different stocking densities. A total of 192 50-week-old Lohmann Brown laying hens were assigned to a 2 × 4 factorial arrangement with two stocking densities, 5 or 7 hens per cage, and four dietary tarragon treatments providing 0, 1, 5, or 10 mmol/kg feed of tarragon-derived additional antioxidant activity for 8 weeks. Serum total protein concentration was not affected by stocking density but increased with tarragon supplementation, rising from 7.5 to 8.3 g/dL. Liver total protein concentration remained unchanged. SDS-PAGE analysis of pooled treatment-group samples identified 24 serum and 39 hepatic protein bands. High stocking density altered the serum lipid profile by increasing cholesteryl ester, free fatty acid, and acylglycerol proportions, as well as total cholesterol and triacylglycerol concentrations, while decreasing triacylglycerol and phospholipid proportions. Tarragon supplementation increased serum cholesteryl ester and phospholipid proportions and reduced serum triacylglycerol and free fatty acid proportions, together with lower total cholesterol and triacylglycerol concentrations. In the liver, high stocking density increased cholesteryl ester and free cholesterol proportions and triacylglycerol concentration, whereas it decreased triacylglycerol and phospholipid proportions and total cholesterol concentration. Tarragon supplementation increased hepatic cholesteryl ester, free cholesterol, and phospholipid proportions and reduced hepatic triacylglycerol proportion and concentration. Significant stocking density × tarragon-derived additional antioxidant activity interactions were observed for serum free fatty acid and hepatic free fatty acid and free cholesterol. Overall, stocking density had a stronger effect on lipid metabolism than on total protein status.