Development of an homologous radioimmunoassay for chicken follicle-stimulating hormone and measurement of plasma FSH during the ovulatory cycle.

1. A highly specific and sensitive homologous radioimmunoassay was developed for measurement of chicken follicle stimulating hormone (cFSH). 2. Mammalian gonadotropin releasing hormone (GnRH) significantly stimulated secretion of chicken luteinising hormone (cLH) but not cFSH when administered to 22 week non-laying hens. 3. Chicken GnRH-I did not affect circulating cFSH concentrations but significantly stimulated cLH secretion when administered to 3 week cockerels. 4. The plasma concentration of cFSH was low throughout the ovulatory cycle, but a significant decline in cFSH occurred prior to the pre-ovulatory LH surge and a significant increase occurred during the 3 hr prior to oviposition as LH levels decline.