Fertilization failure, mostly due to absence of sperm in the oviducts, is a major cause of reproductive inefficiency of farm animals. Sperm may be transported to the oviducts of cattle and sheep within a few minutes after mating or insemination, but these sperm probably fertilize few ova. Slower transport, with establishment of sperm populations in each segment of the reproductive tract, requires a few to several hours. In swine, sperm capable of fertilizing ova reach the oviducts in less than 1 h. Smooth muscle contractions of the reproductive tract, ciliary beats, fluid currents, and flagellar activity of sperm are primary mechanisms of sperm transport. Sperm become hyperactive in the oviducts in association with capacitation. Most sperm in an inseminate drain from the female reproductive tract within a few minutes or hours after insemination; remaining sperm are removed from the tract by slower drainage or phagocytosis. Sperm survival and transport in estrous ewes is reduced drastically by pastures with high estrogen content and by regulating estrus with progestogen or prostaglandin F2 alpha. The cervix is the initial site of inhibition of sperm transport in ewes, and endocrine imbalances probably are the basis of inhibition. Sperm transport problems generally are associated with immobilization and death of sperm in the uterus and anterior segments of the cervix within 2 h after mating. After gilts are inseminated with frozen-thawed semen, relatively few sperm are retained in the reproductive tract, apparently accounting for lowered fertilization rates. Sperm transport has been improved by adding to semen or administering to females such compounds as prostaglandin F2 alpha, oxytocin, estradiol, phenylephrine, or ergonovine. Estradiol, prostaglandin F2 alpha, phenylephrine, and ergonovine administered to rabbits at insemination each increased fertilization rates.
"Additionally, one pregnancy was obtained in a treated animal despite of all these negative factors. Seminal fluid is rich in prostaglandins, especially PGE 2 ; in fact, a higher PGE 2 content has been correlated with increased male fertility in humans . The possibility that the application of Cervidil and the " plugs " , or the process of traversing the cervix using the Guelph method, may have a long-term effect on subsequent fertility is also unlikely. "
[Show abstract][Hide abstract] ABSTRACT: The underlying theme of this study involved the evaluation of the dilatory effects of prostaglandin E2 (PGE2) on the ovine cervix and thus the assessment of its potential applicability to transcervical artificial insemination (TCAI) in ewes. A novel method of PGE2 administration (controlled slow-release vaginal inserts) was examined and the practical implications of this approach including cervical penetrability and post-treatment pregnancy rates were evaluated. The Guelph method of TCAI was performed during the seasonal anestrus (n=40) and the breeding season (n=40) on multiparous Rideau Arcott x Polled Dorset ewes, with or without the pre-treatment with Cervidil® (for a duration of 12 h or 24 h prior to TCAI). Cervical penetration rates averaged 82.5% (66/80) and they did not vary (P>0.05) between the two seasons nor between Cervidil®-treated ewes and their respective controls. Cervidil® priming significantly reduced the total time required for TCAI during the breeding season in comparison to controls (54 sec vs. 98 sec), especially after the 24-h exposure (38 sec vs. 108 sec). The time taken to traverse the uterine cervix was negatively correlated (P<0.05) with the breed (% of Rideau Arcott genotype) and lifetime lamb production in seasonally anestrous ewes. Four out of 36 (11%) successfully penetrated ewes in the breeding season (3 ewes allocated to the 12-h control group and 1 ewe that had received Cervidil® for 12 h) became pregnant and carried the lambs to term. Vaginal mucus impedance (VMI) at TCAI was significantly and positively correlated with the total time (TT) required to complete the procedure in cyclic ewes, and the negative correlation between VMI and TT values at the time of CIDR removal approached to significance in anestrous ewes. The present results indicate a moderate benefit of using Cervidil® for inducing cervical dilation prior to TCAI in ewes, mainly in the breeding season. The specific reason(s) for impaired fertility after the TCAI using frozen-thawed ram semen remains to be elucidated.
"When these rapidly transported sperm were collected and evaluated, most were found to be damaged and immotile—presumably dead or dying (Overstreet and Cooper 1978). It has been proposed that these sperm are byproducts of contractions of the tract that were meant to draw sperm up into the uterus (Overstreet and Cooper 1978; Hawk 1983). In the rabbit, the oviduct appears to be cleared of these sperm before ovulation and therefore they are unlikely to participate in fertilization. "
[Show abstract][Hide abstract] ABSTRACT: The mammalian female reproductive tract interacts with sperm in various ways in order to facilitate sperm migration to the egg while impeding migrations of pathogens into the tract, to keep sperm alive during the time between mating and ovulation, and to select the fittest sperm for fertilization. The two main types of interactions are physical and molecular. Physical interactions include the swimming responses of sperm to the microarchitecture of walls, to fluid flows, and to fluid viscoelasticity. When sperm encounter walls, they have a strong tendency to remain swimming along them. Sperm will also orient their swimming into gentle fluid flows. The female tract seems to use these tendencies of sperm to guide them to the site of fertilization. When sperm hyperactivate, they are better able to penetrate highly viscoelastic media, such as the cumulus matrix surrounding eggs. Molecular interactions include communications of sperm surface molecules with receptors on the epithelial lining of the tract. There is evidence that specific sperm surface molecules are required to enable sperm to pass through the uterotubal junction into the oviduct. When sperm reach the oviduct, most bind to the oviductal epithelium. This interaction holds sperm in a storage reservoir until ovulation and serves to maintain the fertilization competence of stored sperm. When sperm are released from the reservoir, they detach from and re-attach to the epithelium repeatedly while ascending to the site of fertilization. We are only beginning to understand the communications that may pass between sperm and epithelium during these interactions.
Cell and Tissue Research 07/2015; DOI:10.1007/s00441-015-2244-2 · 3.57 Impact Factor
", 1993 ) were increased with el - evated concentrations of circulating estradiol . Sperm transport has been reported to be optimized when females are in estrus or have been under the in - fluence of estrogen ( Hawk , 1983 ) . This increase in sperm transport may be a direct result of alterations in uterine pH . "
[Show abstract][Hide abstract] ABSTRACT: It has been repeatedly demonstrated that estrous expression before fixed-time AI (TAI) results in increased pregnancy success. Therefore, the objective of this experiment was to determine if preblastocyst embryonic developmental characteristics differed from heifers that did or did not exhibit estrus before TAI. Beef heifers ( = 113) were synchronized using the 5-d CO-Synch + controlled internal drug release device with TAI on d 0. Before TAI, estrous expression was assessed twice daily. On d 6, single embryos were collected and visually evaluated to determine quality (International Embryo Transfer Society standards; 1-4, in which 1 = excellent/good and 4 = degenerate) and stage (1-9, in which 1 = unfertilized and 9 = expanded hatched blastocyst). Embryos were stained and evaluated to determine number of dead blastomeres, number of total blastomeres, and number of accessory sperm. Estrous expression before TAI did not affect the percent of embryos recovered ( = 0.59), number of dead cells ( = 0.99), or number of total cells ( = 0.25). However, heifers that exhibited estrus had increased mean ( = 0.03) and median accessory sperm numbers and ( = 0.01) percent live cells when compared with nonestrus heifers. Heifers that exhibited estrus also produced embryos that had a more advanced stage ( = 0.03) and improved quality ( = 0.04) when compared with those heifers not exhibiting estrus. When all heifers were evaluated, there was no correlation between circulating concentration of estradiol at TAI and embryo quality or embryo stage. There was a significant correlation between accessory sperm numbers and embryo quality ( = 0.01) and embryo stage ( < 0.01), such that as accessory sperm numbers increased, embryo quality and stage increased. In conclusion, exhibiting estrus before TAI resulted in improved embryo quality and advanced embryo stage on d 6 and increased the number of accessory sperm associated with the embryo.
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