Circulating levels of luteinizing hormone and androgen in mature male Japanese quail over 24 hours.

Male Japanese quail on a 16 light:8 dark photoperiod (on at 0600 h) were sampled over 24 h to determine peripheral levels of the luteinizing hormone and testosterone. Six males were sampled (each animal sampled once) at each of 10 sampling periods that began at 0800 h and ended the next morning at 0800 h. Serum testosterone concentrations were greatest at 2000 h and decreased across the night (2200 to 0600 h) to reach a nadir at 0500 h; levels increased in the morning but fell again at 1700 h. Luteinizing hormone levels were more constant, with peaks at 1500 and 0200 h.