Study Of Dextran,Carrageenan And Carboxymethyl On Boar Semen Cryopreservation

Semen cryopreservation makes it possible for genetic resources of sires of fine hereditary quality to spread on a global scale,which largely accelerate the genetic updating rate of global graziery.In recent years,artificial insemination has been widely applied to cattle breeding industry,and thus given rise to a matured and integrate industrial chain.However,artificial insemination has not been widely applied to pig raising industry due to several reasons.The main reason was the extreme vulnerability to freezing and sharp change in temperature of boar spermatozoa,which means,inadequate protection during cryopreservation or even procedure could severely damage the boar spermatozoa.These characters largely hindered the research and the development of cryoprotectant of boar semen.After frozen boar sperm was thawed,the sperm motility and viability would significantly drop,and the membrane structure and the acrosome would be severely damaged.These damage would finally lower the insemination rate of the frozen-thawed boar semen and thus obstructed the application of artificial insemination on pig raising industry.In this study,three natural polysaccharides including dextran,carrageenan and carboxymethyl chitosan were investigated to explore their potential as cryoprotectant on boar semen cryopreservation by experiments on sperm motility,viability,plasma membrane integrity,mitochondrial membrane integrity and acrosome integrity.Furthermore,the MDA level and the SOD activity was examined to identify the antioxidative ability of the three polysaccharides.And the results were shown below:1.The addition of dextran to the extender results in a higher sperm quality.The optimal concentration of dextran was determined to be 0.8 mg/mL,of which the motility,viability,mitochondrial membrane integrity,plasma membrane integrity and the acrosome integrity were 52.3%,57,7%,38.3%,56.7% and 60.0%,respectively.The addition of dextran also demonstrated the antioxidative activity by lowered the MDA level to 1.93 nmol/mg protein and increase the SOD activity to 107.1 U/mg protein,which significantly increased the oxidative damage(P<0.05),compared to the control group.2.The addition of carrageenan to the extender significantly increased the sperm quality after cryopreservation(P<0.05).And the optimal concentration of carrageenan was 0.8 mg/mL.Under the optimal concentration,the sperm motility,viability,mitochondrial membrane integrity,plasma membrane integrity and the acrosome integrity has reached 50.3%,55.0%,40.7%,53.7% and 60.3%,respectively.Notably,carrageenan showed high activity as an antioxidant by lowered the MDA level to 1.79 nmol/mg protein and increase the SOD activity to 122.8 U/mg protein.3.The addition of carboxymethyl chitosan to the extender improved the sperm quality after cryopreservation(P<0.05)with an optimal concentration of 0.6 mg/mL.Under the Opimal condition,the sperm motility,viability,mitochondrial membrane integrity,plasma membrane integrity and the acrosome integrity were 52.1%,54.0%,40.5%,52.2% and 59.1%,respectively.More importantly,carboxymethyl chitosan showed the highest antioxidative activity of the three polysaccharides by lowered the MDA level to 1.44 nmol/mg protein and increase the SOD activity to 116.9 U/mg protein.Our results show that supplement of dextran,carrageenan and carboxymethyl chitosan provides significant protection to membrane structures and against the oxidative damage of bovine sperm during cryopreservation.The optimal concentrations are 0.8 mg/mL,0.8 mg/mLand 0.6 mg/mL,respectively.