Seasonal and circadian fluctuation of plasma LH level and its change in the domestic goose as an effect of GnRH treatment.

We have defined the seasonal and circadian changes of the LH level of plasma of 2 years old male and female Hungarian domestic geese by means of the LH antigen-antibody of chickens in the heterologous RIA system. The LH level of plasma in geese living in conditions of natural light does not show any variation resulting from sexual differences, but the application of GnRH analogue (Ovurelin) causes higher peaks in ganders than in females. Since the LH level of plasma at the end of November in sexually inactive birds is high at night and lower during the day; the fluctuation in females can be considered as having a circadian rhythm. Five minutes after the intravenous application of GnRH analogue the LH level reaches its peak in the plasma and this high LH level returns to pre-injection values in 3 hours. The LH level shows a characteristic seasonal cycle in both sexes. The spring peak (reproduction cycle) is followed by a definite decrease at the beginning of the photorefractoriness (mid-June) with a slight automnal increase in female geese.