Effect of zinc supplementation on body and organ weights, certain serum biochemical and endocrinological markers of spent layers

Zinc is the most important micronutrient and enhances overall body performance of the laying hens. Three hundred commercial white leg horn birds of 67 week age were procured from market and the laying hens were supplemented with ZnO (3g/kg) for consecutive three weeks after acclimatization. Body and organs weight of all the spent layers was recorded at the time of each sampling. Serum cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, alanine transaminase (ALT), aspartate transaminase (AST), triiodothyronine (T₃), thyroxine (T₄) and cortisol were studied in the spent layers before and after zinc supplementation. The body and organs weight did decrease significantly in the spent layer supplemented with dietary zinc oxide as compared to the birds before zinc supplementation. Serum total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerides concentration did decrease significantly in the birds after supplementation of ZnO in the diet. The enzymatic activity of ALT and AST significantly increased after zinc supplementation as compared to the birds before supplementation. In the spent layers supplemented with dietary ZnO, triiodothyronine (T₃) concentration was decreased significantly while thyroxine (T₄) and cortisol concentration increased significantly as compared to the spent layers before supplementation. In conclusion, no consistant effects of Zn supplementation were found on body and organ weights, certain serum biochemical and endocrinological markers of spent layers.

Keywords: Spent layers; ZnO, T₃ , T₄ , ALT, AST