Methods to improve the utilization and preservation of gametes in swine
Abstract
The central hypothesis of this thesis is that reproduction in swine can be enhanced through improving methods of preservation and utilization of porcine gametes. Determining the minimum dosage of frozen-thawed (FT) boar semen that yields acceptable reproductive performance (Chapter 2), the impact of ejaculate pH on viability of fresh and FT semen (Chapter 3), and the effects of storage time and temperature on oocyte viability (Chapter 4) were all examined. The effect of boar and FT semen dosage on reproductive success in sows is reported in Chapter 2. Results indicate that both semen dosage and boar from which the ejaculate was collected can impact reproductive potential in sows receiving a single transcervical insemination with FT boar semen. The proportion of sows that conceived following artificial insemination (AI) was greater (P < 0.05) for boar 2 (50.4% ± 0.06) than boar 1 (26.0% ± 0.08). Semen dose influenced (P < 0.05) total fetuses per pregnant sow and total viable fetuses per pregnant sow, with the 0.25 semen dose producing the least number of fetuses and viable fetuses. Collectively, results indicate that if a limited amount of FT semen were available, reproductive efficiency would be maximized by utilizing a FT semen dose between 0.50 and 0.75 x 109 motile sperm cells. In Chapter 3, the effects of pH on the motility and progressive motility of fresh and FT sperm cells were studied. Neat semen pH as well as the difference in pH between the neat semen and extender impacted (P < 0.05) d 1 motility and progressive motility. The extended semen pH tended (P < 0.10) to impact d 1 motility and impacted ( P < 0.05) d 1 progressive motility. For all variables, as the pH became more acidic, sperm motility increased. Also, as the pH difference between neat semen and extender increased, motility decreased. Post-thaw motility and progressive motility were not affected by any of the measured pH parameters. Thus, the reduction in motility observed in FT boar semen appears to be independent of ejaculate pH. In Chapter 4, the effect of storing porcine ovaries for 24 h at various temperatures on oocyte viability was investigated. For all temperatures (4, 17, 37ºC), storage of ovaries for 24 h resulted in a complete loss of oocyte viability as determined by in vitro maturation (IVM) and in vitro fertilization (IVF). Based on cumulus cell matrix scoring immediately after aspiration, oocytes from the 4°C treatment were considered similar to control oocytes, but all oocytes failed to be fertilized and develop into embryos following IVF. Therefore, to optimize the proportion of ooctyes that yield blastocysts following IVM and IVF, oocytes should be aspirated as soon as possible following ovarian collection. Preservation and utilization of porcine gametes has yet to be perfected. However, data from this thesis indicate that when combined with transcervical AI, FT boar sperm can be utilized to achieve satisfactory fertility results in sows, and that among the doses utilized in this study, the dose with the greatest efficacy is 0.75 x 109 motile cells. Ejaculate and extended semen pH do influence fresh semen motility. However, none of the pH parameters evaluated in the current study drastically impacted sperm cell motility following cryopreservation. Lastly, none of the investigated ovarian preservation techniques yielded viable oocytes. Therefore, it is recommended that swine ovarian follicles be aspirated immediately following collection in order to obtain viable oocytes to be used for in vitro maturation and in vitro fertilization. In summary, further investigation into improving methods used to preserve swine gametes as well as the factors that impact the survivability of these gametes following preservation is needed.
Degree
M.S.
Advisors
Stewart, Purdue University.
Subject Area
Animal sciences|Physiology
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