Changes in the serum concentrations of gonadotrophins and oestradiol in peripubertal Chinese Beijing black gilts.

Four gifts of the Chinese Beijing Black breed, all from the same litter, had their blood serum concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH) and oestrogens (E2) measured by radioimmunoassay at intervals of 20 days between the ages of 5 and 185 days. The concentrations of LH declined sharply between days 5 to 25 and remained low until rising again from day 85 and reaching a peak at day 105 before declining again and remaining constant. The concentrations of FSH increased from day 85, peaking at day 105, followed by a slow decline to day 185. Serum E2 concentrations were high at day 5 then decreased dramatically, but increased considerably at 185 days. These results are similar to those reported from European breeds.