Effect of low light intensity on testicular function in photorefractory domestic ganders.
The seasonal variation of the plasma testosterone level of domestic ganders--living under natural photoperiod in Central Hungary--shows a bimodal rhythmicity. An experimental group of ganders within a photorefractory period was exposed to continuous low light intensity (1 lx/m2) from the middle of July until the beginning of August. They were then kept under natural daylight (14.5 L-9.5 D), and then had extra light (14 L-10 D) until the end of the experiment (end of November). The testis weight and the plasma concentration of testosterone were increased significantly as a result of low light intensity but failed to reach the seasonal (February) peak. Having readjusted the birds to natural photoperiod the testosterone plasma concentration did not continue to increase, but decreased slowly for 44 days (16 September). Between the 44th and 52nd day of the experiment (24 September) the testosterone concentration was reduced to the level of the control animals, which were maintained under natural photoperiod. It was established that the photorefractory period had not been terminated by 3 weeks' low light intensity, but a moderate gonadostimulation had occurred. Since photostimulation did not increase the plasma testosterone, but a superactive LH-RH analog increased it significantly in birds which had been in low light intensity, it is supposed that the cause of the refractoriness in ganders may also be decreased gonadotropin-releasing hormone secretion.
D000818:Animals; D005777:Geese / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D008027:Light; D008297:Male; D012621:Seasons; D013737:Testis / Q000187:drug effects / Q000502:physiology*; D013739:Testosterone / Q000097:blood
D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone