The paper was to evaluate the efficient seasons for embryo transfer of cattle in different climatic zones in China. Three climatic zones(mid-temperate zone,warm temperate zone,subtropical zone) were designed,and embryo transfers had been carried out in spring,summer,autumn and winter from 2009 to 2011,respectively. The total number of transplant recipient cattle was 22 208. The results showed that the best seasons for embryo transfers varied with different climatic zones. In mid-temperate zone,summer and autumn were better while summer was the best,and the rate of pregnant was 50. 67%(the number of pregnant cattle was 8 005). In warm temperate zone,spring and autumn were better while autumn was the best,and the rate of pregnant was 54. 99 %(the number of pregnant cattle was 551). In subtropical zone,spring and winter were better while winter was the best,and the rate of pregnant was 56. 94 %(the number of pregnant cattle was 328). The seasonal average temperatures and relative humidity of the best seasons in different climatic zones were concentrated on the same region. In mid-temperate zone,the mean temperature ranged between 22. 4 ℃ and 24. 2 ℃,and the mean relative humidity ranged from 44% to 55. 3%. In warm zone,the mean temperature ranges were between 14. 2 ℃ and 16. 2 ℃,and the mean relative humidity ranges were from 59. 3% to 71. 6%. In sub-tropical zone,the mean temperature ranges were between 3. 26 ℃ and 7. 73 ℃,and the mean relative humidity ranges were from 72% to 80. 6%. Therefore,the optimized conditions of temperature and humidity of season in different zones could be simulated. It is possible that we apply the program to bovine production in the similar agroecological zones,which is of great significance for improving the embryo transfer efficiency of livestock in production.
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