Follicle Stimulating Hormone Increases Serum Oestradial‐17ß concentrations, number of growing follicles and yolk deposition in aging hens (Gallus gallus domesticus) with decreased egg production

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Abstract
1. The aims of this study were to determine if the number of small yellow follicles (SYF) and large white follicles (LWF) in ovaries of young and old hens differed; and if injection of old hens with follicle stimulating hormone (FSH) changed growth of and yolk deposition into follicles of old hens. 2. Ovaries were removed and follicles were divided according to size and condition and counted. The number of normal SYF and LWF was decreased in old hens compared to young hens, whereas the number of atretic follicles was greater in old hens compared to young hens. 3. Old hens were injected subcutaneously with saline containing 0.1% bovine serum albumin (BSA, vehicle) or 12.5, 50, 200, 400 μg porcine (p) FSH or 25 or 50 IU pregnant mare's serum gonadotropin (PMSG) for 5 consecutive days. Blood samples were taken on days 1 and 5 before FSH and PMSG injection and 2 h after FSH and PMSG injection on day 5. Sudan black and Sudan red dyes were injected intravenously on alternative days to monitor yolk deposition into follicles of the hierarchy removed after the fifth day of FSH treatment. 4. Treatment with 200 μg pFSH or 25 IU PMSG for 5 d increased serum progesterone (P4) concentrations as compared to controls. Injection of hens with FSH caused a linear dose dependent increase in serum oestradiol‐17ß (E2) concentrations, dose dependent increase in SYF and LWF, and dose related decrease in number of atretic SYF and LWF. The hierarchy of the ovary was disrupted with PMSG, but not FSH. Larger doses of FSH increased the number of small follicles (10 mm diameter) and yolk deposition. 5. We conclude that small follicles which have not entered the rapid