| The production and application of frozen semen could make full use of the elite livestock genetic resources and improve crossbreeding and improvement efficiency.Ovine spermatozoa are susceptible to cold shock and its semen frozen technology has not been well developed.Dairy Meade is a specific dairy sheep breed from New Zealand.To find out the optimal freezing program for production of Dairy Meade semen straws,current study collected the semen from three Dairy Meade（N1、N2、N3）rams,diluted with commercial OptiXcell（IMV）extender,and produced frozen semen straws with different freezing programs,which had different cooling rates（30℃/min,40℃/min,50℃/min,60℃/min,70℃/min,80℃/min,90℃/min,100℃/min）during the dangerous temperature zone from-10℃to-100℃.The quality of the thawed semen was assessed by viable rate,motility,acrosome integrity,plasma membrane integrity,mitochondria membrane integrity,none-apoptosis rate and embryo cleavage rate after IVF.The results were as follows.1)No significant differences were found of the fresh semen quality from the three rams（N1,N2 and N3）.The viable sperm rate of 30℃/min and 100℃/min group were significantly lower than other groups.2)The VCL,VAP and rapid moving sperm rate of 60℃/min group was significantly higher than other groups.3)The acrosome integrity rates of60℃/min and 70℃/min group were significantly higher（N2 and N3）or had no significant difference with 80℃/min group but significantly higher than the rest groups（N1）.4)The plasma membrane integrity rates of 60℃/min had no significant difference with 70℃/min and 80℃/min group but significantly higher than the rest groups（N1）or had no significant difference with 80℃/min group but significantly higher than the rest groups.5)The mitochondria membrane integrity rates of60℃/min and 70℃/min group were significantly higher than other groups.6)The none-apoptosis rate of 60℃/min group was significantly higher than other groups（N1）or had no significant difference with 70℃/min but significantly higher than the rest groups（N2 and N3）.7)The embryos cleavage rate after IVF by using the sperm of60℃/min group had no significant difference with 40℃/min group but was significantly higher than 30℃/min and 80℃/min group.Combine with above mentioned results from all the 7 assessment parameters under 8 different freezing programs with 3 rams,we concluded that the program with cooling rate of 60℃/min during the-10℃to-100℃period was the best one for Dairy Meade semen freezing.Current study provided the theoretic basis for producing high quality Dairy Meade frozen semen straws. |
