Effect of sperm number and frequency of insemination on fertility of mares inseminated with cooled semen.
Abstract: In this study, we tested the hypothesis that insemination of mares with twice the recommended dose of cooled semen (2 x 10(9) spermatozoa) would result in higher pregnancy rates than insemination with a single dose (1 x 10(9) spermatozoa) or with 1 x 10(9) spermatozoa on each of 2 consecutive days. A total of 83 cycles from 61 mares was used. Mares were randomly assigned to 1 of 3 treatment groups when a 40-mm follicle was detected by palpation and ultrasonography. Mares in Group 1 were inseminated with 1 x 10(9) progressively motile spermatozoa that had been cooled in a passive cooling unit to 5 degrees C and stored for 24 h. A second aliquot of semen from the same collection was stored for an additional 24 h and inseminated at 48 h after collection. Mares in Group 2 were inseminated once with 1 x 10(9) progressively motile spermatozoa that had been cooled to 5 degrees C and stored for 24 h. Group 3 mares were inseminated once with 2 x 10(9) progressively motile spermatozoa that had been cooled to 5 degrees C and stored for 24 h. All mares were given 2500 IU i.v. hCG at the first insemination. Pregnancy was determined by ultrasonography 12, 14 and 16 d after ovulation. On Day 16, mares were administered i.m. 10 mg of PGF2 alpha and, upon returning to estrus, were randomly reassigned to a group for repeated treatment. Semen was collected from one of 3 stallions every 3 d; mares with a 40-mm ovarian follicle were inseminated with semen from the stallion collected on the preceding day. Semen was allocated into doses containing 1 x 10(9) progressively motile spermatozoa, diluted with dried skim milk-glucose extender to a concentration of 25 x 10(6) motile spermatozoa/ml (total volume 40 ml), placed in a passive cooling unit and cooled to 5 degrees C for 24 or 48 h. Response was measured by number of mares showing pregnancy. Data were analyzed by Chi square. Mares inseminated twice with 1 x 10(9) progressively motile spermatozoa on each of two consecutive days had a higher pregnancy rate (16/25, 64%; P 0.10) among stallions (69, 34 and 32%). Interval from last insemination to ovulation was 0.9, 2.0 and 2.0 d for mares in Groups 1, 2 and 3, respectively. Based on these results, the optimal insemination regimen is a dose of 1 x 10(9) progressively motile spermatozoa given on two consecutive days. However, a shorter interval ( 0.9 d) between insemination and ovulation may affect pregnancy rates, and needs to be investigated.
Publication Date: 2000-03-25 PubMed ID: 10732082DOI: 10.1016/S0093-691X(98)00023-5Google Scholar: Lookup
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
The research investigates the impact of sperm count and frequency of insemination on the fertility of mares when inseminated with cooled semen. It specifically focuses on whether a double dosage of semen, or spreading the standard dosage across two days would have a higher pregnancy success rate compared to a single dose.
Research Method
- The study involved a total of 83 cycles from 61 mares. Each mare was randomly assigned to one of three treatment groups upon the detection of a 40-mm follicle.
- Mares in Group 1 were inseminated with 1 x 109 progressively motile spermatozoa, cooled to 5 degrees Celsius and stored for 24 hours. The same collection was used for a second insemination after another 24 hours of storage.
- Group 2 mares were inseminated once with a single dose of 1 x 109 progressively motile spermatozoa that had been cooled to 5 degrees Celsius and stored for 24 hours.
- Group 3 mares received a single insemination with twice the standard dose: 2 x 109 progressively motile spermatozoa, cooled to 5 degrees Celsius and stored for 24 hours.
- All the mares were given a 2500 IU intravenous hCG dose during the first insemination and pregnancy was determined via ultrasonography 12, 14, and 16 days after ovulation.
Results
- Mares from Group 1, which had two consecutive days of insemination, had higher pregnancy rates (64%) than those that had only one instance of insemination, whether it was a single dose (31%) or a double dose (41%).
- There was no significant difference in the pregnancy success rates among the three different stallions that the semen came from.
- The time from the last insemination to ovulation was tracked for the groups: 0.9 days for Group 1, 2 days for Group 2, and 2 days for Group 3.
- The optimal insemination regimen suggested from these findings is a dose of 1 x 109 progressively motile spermatozoa given on two consecutive days.
Additional Considerations
- The researchers suggest that a shorter interval (24 hours or less) between insemination and ovulation might have an impact on pregnancy rates, indicating a potential direction for future research.
Cite This Article
APA
Squires EL, Brubaker JK, McCue PM, Pickett BW.
(2000).
Effect of sperm number and frequency of insemination on fertility of mares inseminated with cooled semen.
Theriogenology, 49(4), 743-749.
https://doi.org/10.1016/S0093-691X(98)00023-5 Publication
Researcher Affiliations
- Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins 80523, USA.
MeSH Terms
- Animals
- Chorionic Gonadotropin / pharmacology
- Female
- Horses
- Insemination, Artificial / methods
- Insemination, Artificial / veterinary
- Male
- Ovarian Follicle / diagnostic imaging
- Ovarian Follicle / physiology
- Pregnancy
- Semen
- Sperm Count
- Sperm Motility
- Temperature
- Ultrasonography
Citations
This article has been cited 1 times.- Brito LFC, Linardi RL, Rosales LAS, Balamurugan NS, Hernández-Avilés C, Ramírez-Agámez L. Evaluation of a Chemically Defined, Long-Term Extender for Liquid Storage of Stallion Semen. Reprod Domest Anim 2025 Sep;60(9):e70126.
Use Nutrition Calculator
Check if your horse's diet meets their nutrition requirements with our easy-to-use tool Check your horse's diet with our easy-to-use tool
Talk to a Nutritionist
Discuss your horse's feeding plan with our experts over a free phone consultation Discuss your horse's diet over a phone consultation
Submit Diet Evaluation
Get a customized feeding plan for your horse formulated by our equine nutritionists Get a custom feeding plan formulated by our nutritionists
