关键词: 马鹿, 甲状腺, 体重, 繁殖活动, 季节性变化

Abstract: This study investigated the role of thyroid function in the regulation of Seasonal
changes of live weight and reproductive activities in red deer ataga． Experiment 1
observed the effects of thyroidectomy(THX)in 3 THX stags from January 1988 to June 1989，with 5 intact stags as controls．M ean plasma concentration of T₃ in co ntrol stags exhibited a seasonal pattern with high levels during spring to early autumn and low levels in autumn and winter．From October 1988 (spring)．control stags exhibited a marked reduction in testicular diameter， accompanied by a decrease of plasma testosterone to undeteetable levels．whereas none of the THX stags expressed these changes． After reaching the nadir in November 1988， testicular diameter of control stags increased abruptly and reached the peak in M arch 1989 (autumn)，which was significantly higher than the peak of THX stags occurring in January 1989． The substantial gain of live weight during December 1988 to March 1989 (summer to autumn)in control stags did not occur in THX stags and these animals had lower (p<0.05)live weight than controls from February 1989．Experiment 2 observed the effects of supplementing T₄ to 4 THX stags from September 1990 on changes in live weight and teaticular activities， with another 4 THX stags as controls． T₄ treated THX stags initially lost weight，but gained more weight during the growing period of spring and summer than control THX stags(p< 0.05)．T₄ treated stags reduced testieular diameter in October and November 1990 (spring and summer) with plasma testosterone concentrations undetectable，but increased thereafter and reached the peak in February 1991 accompanied by a sharp rise of plasma testosterone concentrations． Testicular
diameter of control THX stags had little change in the course of experiment，and these animals maintained high levels of plasma testosterone in spring and summer．Results of this study demonstrate that THX prevented the seasonal changes in live weight and reproductive activities which occur in spring and early summer，and these effects are overcome by treatment with T₄. This indicates that thyroid function is involved in regulation of seasonal changes of live weight and reproduction in red deer stags．

Key words: Red deer stags, Thyroid function, Live weight, Reproduetive activity, Seasonal change