Effect of spermatozoal concentration and number on fertility of frozen equine semen.
Abstract: Information on the number of motile spermatozoa needed to maximize pregnancy rates for frozen-thawed stallion semen is limited. Furthermore, concentration of spermatozoa per 0.5-mL straw has been shown to affect post-thaw motility (7). The objectives of this study were 1) to compare the effect of increasing the concentration of spermatozoa in 0.5-mL straws from 400 to 1,600 x 10(6) spermatozoa/mL on pregnancy rate of mares, and 2) to determine whether increasing the insemination dose from approximately 320 to 800 million progressively motile spermatozoa after thawing would increase pregnancy rates. Several ejaculates from each of 5 stallions were frozen in a skim milk-egg yolk based freezing medium at 2 spermatozoal concentrations in 0.5-mL polyvinyl-chloride straws. Half of each ejaculate was frozen at 400 x 10(6) cells/mL and half at 1,600 x 10(6) cells/mL. Insemination doses were based on post-thaw spermatozoal motility and contained approximately 320 x 10(6) (320 to 400) motile spermatozoa or approximately 800 x 10(6) (800 to 900) motile spermatozoa. Sixty-three mares were assigned to 1 of 4 spermatozoal treatments (1--low spermatozoal number, low concentration; 2--low spermatozoal number, high concentration; 3--high spermatozoal number, low concentration; 4--high spermatozoal number, high concentration) and were inseminated daily. Post-thaw spermatozoal motility was similar for cells frozen at both spermatozoal concentrations (P > 0.1). One-cycle pregnancy rates were 15, 40, 28 and 33%, respectively, for Treatments 1, 2, 3 and 4. Packaging spermatozoa at the high concentration tended to increase pregnancy rates vs packaging at the low concentration (37 vs 22%; P = 0.095). Furthermore, when the lower spermatozoal number was used, there tended (P < 0.1) to be a higher pregnancy rate if spermatozoa were packaged at the higher concentration. There was no increase in pregnancy rates when higher numbers of motile spermatozoa were inseminated (27 vs 31%; P > 0.1). Based on these results, a single 0.5-mL straw dose containing 800 x 10(6) spermatozoa should be used and each insemination dose should contain approximately 320 x 10(6) motile spermatozoa. Fertility trials utilizing other freezing extenders are necessary before recommending a single 0.5-mL insemination dose for all freezing extenders.
Publication Date: 2000-03-25 PubMed ID: 10732017DOI: 10.1016/s0093-691x(98)00099-5Google Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This study examines the influence of sperm concentration and number on the fertility rates resulting from the use of frozen stallion semen. The researchers found that a higher sperm concentration tended to improve pregnancy rates, but increasing the number of motile spermatozoa used in insemination did not markedly improve these rates.
Objective and Methods
- The study aimed to explore two main facets. Firstly, it sought to observe the impact of higher concentration of spermatozoa – from 400 to 1,600 million per 0.5-mL straw – on the pregnancy rate of mares. Secondly, it aimed to discern whether increasing the insemination dose from about 320 to 800 million progressively motile spermatozoa would augment pregnancy rates.
- The experimental process involved freezing multiple semen samples from each of 5 stallions in a medium made of skim milk and egg yolk. Every semen sample was split into two, with one half frozen at 400 million cells/mL and the other half at 1,600 million cells/mL.
- Insemination doses were determined based on sperm motility after thawing and contained approximately 320 to 400 or 800 to 900 million motile spermatozoa.
- Sixty-three mares were allotted to one of four sperm treatments, which varied in sperm count and concentration, and were inseminated daily.
Results
- Post-thaw sperm motility was similar for semen frozen at both concentrations. This indicates that varying concentration levels did not detrimentally affect sperm vitality.
- Pregnancy rates for the four different treatments ranged from 15% to 40%. These cervical insemination data suggested that packaging sperm at a higher concentration was associated with increased pregnancy rates, compared to packaging at a lower concentration. Interestingly, increasing the number of motile sperm in the insemination dose did not correspondingly increase pregnancy rates.
Conclusions and Implications
- The study concluded that a single 0.5-mL straw dose containing 800 million spermatozoa should be used for insemination, with each dose containing approximately 320 million motile spermatozoa.
- However, the researchers caution that fertility trials using other freezing extenders should be conducted before generalizing this insemination dose. Thus, while the research provides useful insights into sperm concentration and number effects on fertility, it is applicable only to the specific freezing medium used in the study. Equine practitioners and reproduction scientists may need to customize strategies based on particular freezing extenders used in their processes.
Cite This Article
APA
Leipold SD, Graham JK, Squires EL, McCue PM, Brinsko SP, Vanderwall DK.
(2000).
Effect of spermatozoal concentration and number on fertility of frozen equine semen.
Theriogenology, 49(8), 1537-1543.
https://doi.org/10.1016/s0093-691x(98)00099-5 Publication
Researcher Affiliations
- Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins 80523, USA.
MeSH Terms
- Animals
- Cryopreservation / methods
- Cryopreservation / veterinary
- Enzyme Inhibitors / therapeutic use
- Female
- Gonadotropin-Releasing Hormone / analogs & derivatives
- Gonadotropin-Releasing Hormone / therapeutic use
- Horses / physiology
- Insemination, Artificial / veterinary
- Male
- Pregnancy Rate
- Random Allocation
- Semen / physiology
- Semen Preservation / methods
- Semen Preservation / veterinary
- Sperm Count / veterinary
- Spermatozoa / physiology
- Triptorelin Pamoate / analogs & derivatives
Citations
This article has been cited 1 times.- Dong Q, Rodenburg SE, Huang C, VandeVoort CA. Effect of pre-freezing conditions on semen cryopreservation in rhesus monkeys.. Theriogenology 2008 Jul 1;70(1):61-9.
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