Abstract: [Objective] Reproductive initiation in animals is based on gonadotropin-releasing hormone （GnRH）,the release of GnRH in non seasonal estrous animals such as cows is controlled by negative feedback from progesterone,meaning that changes in the estrus cycle of cows are regulated by progesterone levels. Progesterone not only controlled estrus of dairy cows,but also affected oocyte quality,dominant follicle size,ovulation,conception,twin rate and promoting endometrial development,inhibiting contraction,pregnancy maintenance and other physiological changes during the dominant follicle period.Due to food safety concerns,progesterone preparations for injection in production have been banned during the lactation period of cows. The progesterone preparations allowed for lactating cows in China are intravaginal progesterone insert. At present,the products used are mainly imported progesterone suppository products. In order to support the development of China's dairy industry and reduce medication costs, domestic research and development have begun to produce this type of product. In June 2019,a trial was conducted to compare the differences between domestic intravaginal progesterone insert（Xida）and similar imported original research products. [Method] By detecting the changes in progesterone levels in the blood of cows in the experimental group （Xida Suppository） and the control group （original research progesterone Suppository） before,48 h after and 7 days after suppository withdrawal. The proportion of progesterone residue in the silicone plug after use was detected. Also compare the changes in blood drug concentration at the above time points during the second use of the old suppository and the situation of pregnancy after insemination. [Result] There was no difference in the changes in blood progesterone concentration and the proportion of progesterone residue in the suppository between the two products after use （P>0.05）. There was no significant difference in the pregnancy rate between the two groups when the products were used for the first time and reused for the second time （P>0.05）. [Conclusion] The use of Xida Suppository in cows has a stable effect and can replace the original progesterone suppository in production,and it is not recommended to use it again.

Key words: dairy cow, intravaginal progesterone insert, regular transfusion, progesterone concentration