Investigation Of Goat Sperm Metabolism During Long Term Liquid Storage Of Goat Semen

Sperm preservation contributes to the expansion of reproductive techniques, such as artificial insemination (AI) and in vitro fertilization(IVF). Preservation techniques could be used as an additional method to promote genetic progress in domestic animals,mainwhile,it is essential in breeding and selection schedules contributing to increase production of domestic species. The main method of preservation of semen is cryopreservation,while freezing sperm is an expensive process because cryopreservation causes damage and some loss of spermatozoa,for example ultrastructural, biochemical and functional damage etc which may resulting in a decline in motility and viability. Moreover pregnancy is low(about 50%)by AI with frozen semen, which limits application of the AI. So liquid-stored spermatozoa can be an alternative to frozen–thawed spermatozoa for AI, because freezing sperm is an expensive process.Thus, long term liquid storage of goat sperm is desirable, as it would confer greater flexibility to breeding farms. While studies on liquid storage of goat semen are few especially investigation of metabolism mechanism of goat spermatozoa during long term liquid storage. Motility and fertilizability of sperm during storage is influenced by so much factors as electrolyte, oxidative stress, metabolic acidosis, DNA fragmentation, Shedding off specific lipid constituents from sperm cell membrane during preservation, acrosome reaction and spontaneous capacitation etc. Discovering and eliminating these disadvantage factors, constructing a chemically defined extenders and an efficient semen storage system is inevitable for generalization of fertilization in vitro and artificial insemination. Therefore, the application of chemically defined extenders will have obvious advantages in long term liquid storage of buck semen. At the same time this system will provid a platform that we can use to investigate metabolism mechanism of goat sperm during long term liquid storage.The aim of the present study was to increase the in vitro viability of goat sperm after semen storage by optimizing procedures for semen processing and storage in phosphate buffer saline.The effects of calcium ion, magnesium ion,coating with egg yolk,storage temperature and cooling rate during semen storage on goat sperm viability were investigated and an optimized protocol was obtained for liquid storage of goat semen. Meanwhile investigation of goat sperm metabolism mechanism during long term liquid storage were carried out . The results of this study indicate that1) Motility and viability of goat sperm is significantly lower if the semen is stored in PBS supplemented with Ca2+ and Mg2+ regardless of sperm coating or not during semen collection when the semen is stored at 5℃.2) Motility and viability of goat sperm is significantly higher if the semen is stored in PBS supplemented with 144mM glucose regardless of sperm coating or not during semen collection when the semen is stored at 5℃.3) Motility and viability of goat sperm is were significantly higher in coated semen than in non-coated semen when the semen is stored at 5℃.4) Motility and viability of goat sperm is were highest in non-coated semen when the semen is stored at 15℃, compare to 5℃and 25℃.When the non-coated semen was stored at 15℃, a sperm motility of 30% was maintained for 7 days.We have constructed a an efficient semen storage system whose constituent is simple and chemically defined.5) Motility and viability of goat sperm is were highest in non-coated semen if the semen is stored in PBS supplemented with 3mM glucose when the semen is stored at 15℃,and a sperm motility of 30% was maintained for 9 days. However motility and viability of goat sperm is lower if the concentration of glucose exceeding 5mM/L and a sperm motility of 30% was maintained for only 3 days.6) Motility of goat sperm extendered in PBS containing glucose supplied with iodoacetate,inhibitor of glycolysis,were lower significantly than the control which didn't contain iodoacetate.Meanwhile the time of sperm motility of exceeding 30% maintained for declined significantly.7) Motility of goat sperm extendered in PBS containing glucose supplied with dehydroepiandrosterone,inhibitor of pentose phosphate pathway,were not significantly lower than the control which didn't contain dehydroepiandrosterone,and the time that motility of sperm exceeding 30% maintain for were not declined significantly. 8) Motility of goat sperm were lower significantly in non-coated semen if the semen is stored at 15℃during winter than during other seasons.While motiliy can be elevated significantly if the sperm is coated with egg yolk during semen collection.It is concluded that for liquid storage of buck semen:1)It is unfavourable for sperm's survival if the extender is supplemented with Ca2+,Mg2+ during long term liquid storage;2) It is favourable for sperm's survival if the extender is supplemented with glucose during long term liquid storage at 5℃; 3) It is favourable for sperm's survival if the sperm is coated with egg yolk during semen collection when the semen is stored at 5℃; 4) It is favourable for sperm's survival in non-coated semen when the semen is stored at at 15℃;5) It is favourable for sperm's survival if the semen is extendered in PBS supplemented with 3mM/L glucose compare to the other concentration at 15℃if the semen is extendered directly after collection without coating with egg yolk; However It is unfavourable for sperm's survival when the concentration of glucose exceeding 5mM/L;6) Sperm metabolizes glucose by glycolysis pathway,because of inhibiting glycolysis pathway influence sperm's survival during long term liquid storage at 15℃;7)Sperm metabolizes glucose not by pentose phosphate pathway,because of inhibiting pentose phosphate pathway didn't influence sperm's survival during long term liquid storage at 15℃.