The present studies examined the effects of photoperiod changes during growth and early reproduction on secretory patterns of LH and T in male turkeys. The results demonstrated age-related and photoperiod-related changes in plasma LH and T levels. This is the first study to report in detail the pulsatile changes in circulating LH and T in male birds in relation to the initiation of reproduction. Circulating levels of LH and T were characterized into three different patterns: 1) before sexual maturation, low baseline levels of both LH and T with detectable pulses of both hormones; 2) after sexual maturation, high baseline levels of both LH and T with detectable pulses of both hormones; and 3) after photostimulation of photosensitive male turkeys, high baseline levels of both LH and T with detectable pulses of LH but few detectable pulses of T. antibiotic levaquin
Before secretory patterns of LH and T were determined, two trials were conducted to ascertain developmental patterns of the hormones in male turkeys exposed to the various photoperiods. In trial 1, increases in levels of LH and T occurred at about 18 wk of age under either LD or SD lighting, and the results of trial 1 were confirmed and extended in trial 2.