Author
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WULSTER-RADCLIFFE, MEGHAN - B.A.S. FORMER ARS |
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Lewis, Gregory |
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Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only Publication Acceptance Date: 2/1/2002 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: The difficulty of traversing the cervix severely limits the use of transcervical (TC) AI in sheep. In an attempt to overcome the problems associated with TC intrauterine AI (i.e., trauma induced as the instrument is manipulated through the cervix and into the uterus), a new TC AI instrument was developed. Neither this instrument nor passing it through the cervix effects semen characteristics, fertilization, or pregnancy rate through d 3; however, it is unknown if this instrument or passage of the instrument through the cervix effects pregnancy rates after d 3 of pregnancy. Thus, experiments were conducted to determine whether this TC AI instrument and(or) using this instrument to perform TC AI affected pregnancy rate. To synchronize estrus in all experiments, progestogenated pessaries were inserted and left in place for 12 d. On d 5 after pessary insertion, 15 mg of Lutalyse were injected i.m. At pessary removal, 400 IU of eCG were injected i.m. In ewes were artificially inseminated, inseminations were performed 48 to 52 h after pessary removal. Fresh, diluted semen (200 microliters) pooled from the same nine rams each day during the experiment was used. If ewes were exposed to rams, than ewes were exposed to rams individually until the rams mounted and ejaculated or for a maximum of 20 min. If a ewe would not stand to be mounted, she was removed from the experiment. In Exp. 1, ewes were assigned to one of three treatments: 1) TC intrauterine AI using the new TC AI instrument + sham intrauterine AI via laparotomy (n = 29); 2) sham TC AI + intrauterine AI via laparotomy using a proven laparoscopic AI instrument (n = 29); and 3) sham TC AI + intrauterine AI via laparotomy using the new TC AI instrument (n = 30). Approximately 14 d after AI, uteri were collected and flushed. Embryos were recovered and evaluated morphologically for development. Treatments significantly affected pregnancy rate ([ewes pregnant ¸ number of ewes] ´ 100; P < 0.05). Transcervical deposition of semen significantly reduced pregnancy rate (17.2 vs 61%); however intrauterine deposition of semen using the TC AI instrument via midventral laparotomy significantly increased pregnancy rate (76.6 vs 44.8%). In Exp. 2, ewes were assigned to one of two treatment groups: 1) sham cervical manipulation (n = 40) or 2) cervical manipulation via mimicing TC AI (n = 40). Immediately after treatment, ewes were individually exposed to rams until bred. In Exp. 3, ewes were assigned to one of two treatment groups: 1) TC AI (n = 99) or 2) laparoscopic AI (n =99). Twenty five and 56 d after, pregnancy was determined in ewes in Exp. 2 and 3 using transrectal ultrasonography. In Exp. 2, no significant differences in pregnancy rate on d 30 or d 50 were found following sham treatment or traversing the cervix with the TC AI instrument when the rams were used to deposit the semen (mean = 66%). In Exp. 3, significantly fewer animals were pregnant on d 30 following TC AI (5 vs 45%; P < 0.01). Loses between d 30 and d 50 were not significantly different between the two groups. Following natural service (i.e., deposition of a large number of sperm cells), there are no difference in pregnancy rate after mimicing TC AI; whereas, the use of TC AI to deposit semen (i.e., a fixed lower number of sperm cells) results in a marked reduction in pregnancy rate, suggesting that sperm numbers as the limiting factor in effective use of TC AI in sheep. |
