Development and Fine Structure of the Reticulate Scales of the Turkey Foetuses with Regard to Occurrence of the Food Pad Lesions in Turkey Poults

Abstract

Introduction: Most of the morphological studies on the skin of birds refer to chickens. Little can be found about the specific fine structure of the foot‐pad epidermis of turkeys and almost nothing is known about the developing reticulate scales in turkey foetuses. This study deals with the question as to whether the development and morphology of the reticulate scales of turkeys are similar to those of chickens. Since the first signs of food‐pad dermatitis can be observed in turkey poults at the age of four days, it was additionally examined if these alterations can be found in turkey foetuses already.Methods: Foot pad samples of heavy strain BUT Big 6 turkeys were collected at different developmental stages (day 20, 23, and 28 of incubation). The specimens were compared by light‐ and electron‐microscopic methods.Results: On the 20th day of incubation, the reticulate scales cover the food pads as small knob‐like structures. Between the embryonic epidermal cells wide inter‐cellular spaces are visible, and in the intermediate cells multigranular bodies (MGBs) are detectable. Peridermal cells cover the reticulate scales. They are characterized by peridermal granules and protuberances of the outer cell membrane. On the 23rd day of incubation, many lipid droplets are scattered within the intermediate cells. Because a thin stratum corneum has formed, the periderm is almost completely sloughing off. On the 28th day of incubation, the turkey poults hatch. The epidermis has almost reached maturity and a broad stratum corneum is detectable.Conclusions: The development and morphology of the reticulate scale epidermis of turkey is comparable to that of chicken, although little differences were found. Besides former investigations, which described the peridermal protuberances as microvilli, scanning‐electron microscopy proved that they also show a fingerprint‐like surface structure that has not been observed for birds previously. Up to the hatching day, no signs of food pad alterations are seen in developing turkeys.