Histomorphometrical and Histopathological Assessment of in Ovo Methionine Injection on the Skin Layers and Its Collagen Bundles of Chicken Embryo

Introduction: Skin resistance is greatly dependent on its collagen amount and nutritional&nbsp;substances such as crude protein that affect the skin collagen can indirectly influence the skin&nbsp;resistance and increase its strength. In this regard, this study aimed to evaluate the effect of in&nbsp;ovo methionine injection on histomorphometry of the skin layers. Methods: Thirty fertilized eggs of Ross 308 broiler chicks were randomly divided into 3&nbsp;equal groups of 10 eggs each. On day 4 of incubation, the first and the second group (treatment&nbsp;groups) were injected by 40 mg and 50 mg of methionine (Met) dissolved in 0.5 mL of&nbsp;phosphate buffered saline into the yolk sac, respectively. The third (control) group was only&nbsp;received 0.5 mL of phosphate buffered saline. On the day 18 of incubation, the eggs were&nbsp;removed from the incubator and the embryos were killed humanely. Then, the samples were&nbsp;taken from the skin of thoracic region of each embryo for histomorphometric study under the&nbsp;light microscope. Results: The results indicated no significant increase in the epidermal thickness in Met&nbsp;(treatment) groups except for Met 40 compared to controls and Met 50 (P<0.05). Dermal&nbsp;thickness in the Met groups showed significant increase in Met 50 group compared to the other&nbsp;groups (P<0.05). Collagen bundles thickness of both dermis layers decreased in Met groups. Conclusion: Obtained results revealed that methionine may stimulate immature collagen&nbsp;synthesis.