RESUMEN
Effect of short photoperiod (SP; LD 6:18) treatment on serum hormone profile and growth rate of adrenal, thyroid, ovary, oviduct, liver and lymphoid organ was studied in rearing pullets (RIR breed) of 1 to day 90 old. Body weight and growth index of SP pullets were lesser as compared to pullets reared under LD 12:12. Except for ovary (recorded marginal increment), weights and growth indices of thyroid, adrenal and oviduct decreased under SP. Weight of liver and lymphoid organs was higher at 30 and 90 days, in SP pullets as compared to LD 12:12. Histometric data suggested that the transition from small to big follicles was slow in ovary of SP pullets, and also reduced follicular atresia was noted in SP pullets. Except for higher corticosterone level at 30 days and higher progesterone level at 30 and 60 days, relative levels of all the hormones at all other ages were lower in SP pullets. In general, the present observations suggested intraovarian changes in pullets exposed to SP.