types of flaxseed (no processing, milled and extruded) on egg performance, egg yolk fatty acids (FAs), and lipids components in yolk and blood of Hy-Line W-36 75-week-old for nine weeks. We allocated 300 laying hens to ten treatments, including control and three inclusion levels (3, 6, and 9%) of three processed methods (whole, WF; milled, MF; and extruded, EF). Each treatment had six replicates containing five hens each. Egg performance, Haugh unit, feed intake, and egg production increased concomitantly with enhancing the percentage of flaxseed in diets. In contrast, shell thickness, shell strength, yolk weight, feed conversion efficiency, and egg mass remained unchanged. Interestingly, the extrusion method had positive effects on egg weight, egg production, feed intake, and egg mass contents, unlike other groups. In respect of yolk FAs, as predicted, individuals fed the 9%EF (9.31 g/100 g) diet had the highest value of n-3 fatty acids. Consequently, n-6/n-3 ratio was improved from 9.20 g/100 g in the yolk of chicks fed the control diet to 1.26 g/100 g in hens fed the 9%EF diets. While cholesterol (CHO) in yolk, egg, and blood of hens fed 9%EF diet were significantly lower than control, total protein in blood was significantly higher than control (P < 0.05). Although superoxide dismutase in the blood of birds fed the control diet was significantly higher than those fed 9%EF diets, serological enzymes in laying hens were not affected by experimental diets. In conclusion, feeding birds with 9%EF significantly improved most of the egg quality parameters, FAs profile, blood factors, and antioxidant capacity. Therefore, extruded flaxseed up to 90 g/kg can be used as a useful method towards improving the productive performance of old laying hens in a commercial-scale study without impairing the antioxidant system and inducing liver damage.

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