关键词: 大熊猫, 精液, 解冻速度, Pentyoxyfilline

Abstract: A management priority for giant pandas is developing cryopreserved sperm banks to use in conjunction with artificial insemination to protect extant diversity and transport genetic material between geographically disparate panda populations. To be an effective tool , these banks , sperm viability post-thaw must be optimized. These studies examined the influence of 1) different thaw rates and 2) the chemical stimulant pentyoxyfilline (PF) , on sperm viability and motility cryopreserved at rapid rates ( - 40 to -100 ℃/ min) . Semen was collected from 11 adult giant pandas and cryopreserved rapidly ( - 40 to - 100 °C/ min) . In study Ⅰ, sperm was thawed at various rates by plunging into water baths at (1) 22 ℃ ( slow rate thawing) ; (2) 37 ℃ (intermediate thaw rate) ; or (3) 50 ℃ (rapid thaw rate) . When compared to mean pre-freeze giant panda sperm motility (78.1 ±2.9 %) , post-thaw motility decreased ( P < 0.05) after rapid (57.5 ±5.4 %) thawing. However , the intermediate (67.5 ±3.1 %) or slow (73.33 ±2.1 %) thawing rates were comparable to the pre-freeze value. In study Ⅱ, sperm was thawed at the intermediate rate and exposed to 0mM, 1mM, 5mM and 10 mM PF for short (15 min) and long periods (24 hrs) . Sperm samples exposed to PF for 15 min at (0mM, 1mM, 5mM and 10 mM) had similar ( P > 0.05) sperm motility , progressive status , viability and acrosomal integrity patterns throughout the 90 min examination period. Long-term incubation with 1 mM PF , did not influence motility among time periods ( P > 0.05) . Giant panda sperm incubated with 5mM and 10 mM PF were less ( P < 0.05) motile by 4 hrs (5 mM: 24.0 ±4.7 ; 10 mM 19.5 ±3.6 %) compared with controls (38.3 ±5.2 %) . Additionally , sperm incubated with 10 mM PF had
fewer ( P < 0105) intact acrosomes (56.3 ±2.8) after 4 hrs incubation , compared with controls (71.0 ±3.3 %). These two studies of giant panda sperm demonstrated that giant panda sperm that are cooled and cryopreserved rapidly in pellet form , have better survival following slow rate thaw. Further , giant panda sperm are sensitive to the common motility enhancer PF. However , this boost is short-term , actually depressing sperm motility after a few hours of incubation and , at higher concentrations , damaging acrosomal integrity.

Key words: Giant Panda, Semen, Thawing rate, Pentyoxyfilline