Effect Of Cryopreservation On Sperm Quality In Pigs

China is the world’s largest producer and consumer of pork,and it is also the world’s largest pig breeding market.Artificial insemination is the main way of pig breeding and reproduction.More than 90% of semen used in artificial insemination is fresh semen,and the use of frozen semen accounts for less than 1%.Compared with fresh semen,frozen semen has many advantages,such as artificial insemination without being limited by geographical environment,time and other factors;However,frozen semen also has disadvantages,for example,the fertilization rate of frozen sperm sows,the farrowing rate is not as good as fresh semen,so it cannot be widely used in production.The fertilization rate of frozen semen of pigs has a certain gap compared with that of frozen semen of cattle and sheep.The research on improving the fertilization rate of pig frozen sperm at home and abroad mainly focuses on semen diluent components,cryoprotectant types and cryopreservation procedures.It has been found that sperm fertilization rate is related to such factors as viability,acrosome and plasma membrane integrity,antioxidant capacity,etc.The related physiological indexes of fresh and frozen semen were detected and compared in the experiment.In addition,according to the relevant literature,a natural lipophilic compound,resveratrol,was added into the cryopreservation solution and tested for its effects on the plasma membrane,acrosome,sperm nuclear DNA,mitochondrial activity,and antioxidant capacity of frozen porcine sperm.The results of the study are as follows:1.Cryopreservation results in a significant decrease in sperm motility in pigs.The viability of swine fresh sperm was 78%,and the recovery activity of sperm after freezing was 41%,which showed that the sperm motility caused by cryopreservation was significantly reduced(P<0.01);The rate of dead sperm(23.53%)after cryopreservation was significantly higher than that of fresh sperm(0.10%),and the difference between the two was significant(P<0.05);The intact live sperm of the apical body after freezing was11.33% significantly lower than that of fresh sperm,and the number of sperm in the broken apical body was significantly increased due to cryopreservation(P<0.01);The number of sperm with high mitochondrial membrane potential after cryopreservation was significantly reduced by 51.83% compared with 93.3% of fresh sediment,and the difference between the two was very significant(P<0.01).2.Cryopreservation leads to a decrease in the antioxidant capacity of porcine sperm.Compared with fresh sperm,the sperm T-AOC level,GSH-Px activity decreased significantly(P<0.01),SOD activity decreased significantly(P<0.05),and cryopreservation led to a significant increase in the content of toxic substances in sperm(P<0.01)and ROS levels(P<0.05).3.Cryopreservation leads to changes in the ultrastructure of porcine sperm.Compared with fresh sperm,the apical body of the sperm after freeze-thaw is ruptured,or even completely lysised,and the apical body enzyme flows out;Partial breakage of the plasma membrane,partial lysis;Fractures occur at the joint of the neck,and part of the sperm is separated from the head and tail;The mitochondrial sheath of the middle segment of the tail is blurred and unevenly arranged,and the outer membrane of the middle and posterior segment of the tail is broken;The 9+2 structure shows blurred and uneven distribution;Partial sperm lysis as a whole.4.The addition of resveratrol to the porcine semen freezing solution can significantly improve the quality of sperm after freeze-thaw.Sperm breakage mortality,mitochondrial membrane potential,total antioxidant capacity(T-AOC),superoxide dismutase(SOD)activity,glutathione peroxide(GSH-PX)enzyme activity,toxic substance malondialdehyde(MDA)content,ROS levels were significantly improved compared with the unadded Res group.In summary,freezing will lead to pig sperm membrane damage,mitochondrial activity decreased,sperm reactive oxygen species level increases,the addition of resveratrol before sperm freezing can significantly improve the damage of frozen process to pig sperm,thereby improving the quality of frozen sperm,for the application of resveratrol in pig semen protectant to provide experimental basis.