The University of Arizona

The influence of exogenous PGF2a on spermatozoa motility and fertility*

-L. Penrod, K. Adams, M. J. Arns
Department of Animal Sciences, University of Arizona, Tucson, AZ. USA 85721

Introduction

Breeders in several animal industries have used PGF2a to induce and synchronize estrous cycles and parturition. Recently, PGF2a has been found to enhance the mode of transportation by which the sperm travel through the female reproductive tract. Sperm are normally transported through the female genital tract via passive and active transport. Passive transport involves muscle contractions, while active transport consists of intrinsic movement of sperm. Prostaglandin F2a causes uterine smooth muscles to contract. These contractions aid in expulsion of any remaining fluid, (i.e. from inflammation) or following artificial insemination and potentially aid in the sequestration of sperm at the utero-tubal junction. Previous studies in swine have demonstrated an increase in conception rates and total piglets born when PGF2a was added to extended semen. Problems associated with AI breeding techniques have led to many infertile mares due to overwhelming inflammation, contamination, and other adverse reactions. Imprecise timing using AI techniques can create lower number of viable sperm reaching the oviduct at the time of ovulation, contributing to poor conception in the mare.

The objectives of this study were to determine the effects on sperm motility and fertility when extended semen was enriched with PGF2a.

Materials & Methods

Three ejaculates from each of three mature stallions of known fertility were utilized to determine the influence of increasing concentrations of PGF2α (Lutalyse, The Pharmacia-Upjohn Co., Kalamazoo, MI) on sperm motility. Gel-free semen was diluted with a skim milk-glucose extender to a final concentration of 25 million progressively motile sperm/ml. Aliquots of extended semen contained 0, 33, 63, 94, or 125 μg/ml PGF2α. The percentage of progressively motile spermatozoa (PMS) was determined in a double blind fashion following 15 and 240 min of incubation at 37 oC, and following 24 h of cold storage (5 oC). Motility data were analyzed using PROC MIXED of the Statistical Analysis System (SAS, 2001).

Six mares of quarter horse and thoroughbred breeding were utilized to determine the influence of PGF2α -enriched semen on fertility. Mares were randomly assigned to be bred with non-enriched or PGF2a -enriched semen. Gel-free semen was diluted with SKMG containing 0 or 125 μg/ml PGF2a. Inseminations alternated within mare over a total of four estrous cycles. During the first two cycles, mares were bred with semen containing 100 million progressively motile sperm per dose. During the remaining two cycles mares were bred with semen containing 200 million progressively motile sperm per dose. Mares were bred every other day beginning when mares showed estrous behavior and had a minimum of a 35 mm follicle. Pregnancies were determined ultrasonically on day 14 post-ovulation. Overall pregnancy rates were compared using Chi-square analysis.

Results

Increasing concentrations of PGF2a had no affect on PMS at any of the time points evaluated (Figure 1). The per cycle pregnancy rates (Table 1) were low in this study. In an attempt to evaluate the influence of PGF2α-enriched semen, a “low fertility” model was used. In the first set of cycles the insemination dose was 100 million progressively motile sperm, while in the second set of cycles, the dose was increased to 200 million progressively motile sperm. One of the mares entered anestrus and was not bred during the last cycle. Overall, there was no difference in per cycle pregnancy rates between mares inseminated with PGF2α-supplemented semen and those inseminated with non-supplemented semen.

Figure 1

Figure 1. Mean percentages of progressively motile sperm in response to increasing concentrations (μg/ml) of PGF2α. Means within time did not differ (P>.05).

Dose +PGF2α -PGF2α
100 x 106* 17% (1/6) 0% (0/6)
200 x 106* 40% (2 /5) 50% (3/6)
Overall 27% (3 /11) 25% (3 /12)

Table 1. Per cycle pregnancy rates for mares bred with non-supplemented and PGF2α supplemented semen.

Conclusion

The inclusion of PGF2α in semen extenders for stallions does not appear to alter sperm motility, however the data does not support any beneficial effects of including PGF2α in semen extenders for enhancing fertility.

*Study to be presented at IX International Symposium on Equine Reproduction, August 2006

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