Chabro is a strain of poultry birds especially designed for backyard farming and is more adoptive to climatic variations in the tropics. The thyroid gland plays an important role in controlling basal metabolic rate. Histochemical changes of the gland in association with seasonal changes have not been studied so far in Chabro chicken. The present study describes the season related variations in the histochemistry of thyroid gland. Methods: The histochemical study was conducted on thyroid gland

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... eight to ten weeks old 24 apparently healthy Chabro chickens procured from Poultry Farm, DUVASU, Mathura. The birds were divided into two groups consisting of 12 chickens in each group reared in summer and winter seasons.Result: The capsule showed mild reaction for PAS, protein and glycogen. Follicular cells showed intense reaction for bound lipids, protein and alkaline phosphatase. The colloid in summer season showed strong reaction for PAS at periphery and very strong reaction at center while in winter colloid showed strong PAS positive activity. The Chabro chicken thyroid was functionally more active in winter as compared to summer season because of increased diameter of all follicles and concentration of thyroid hormones level in winter season.