Choosing the right breeding method for your mare is a critical decision that can significantly impact success rates and overall management. This guide explores the advantages and considerations of three primary breeding techniques: live cover, chilled semen insemination, and frozen semen insemination, providing valuable insights for horse owners and breeders.
Live Cover Breeding: The Traditional Approach
Live cover, or natural breeding, has been practiced for centuries and offers several advantages depending on your specific circumstances. The fundamental requirement for successful live cover is that the mare must be in standing heat (estrus) and receptive to the stallion at the time of service. This ensures the safety of handlers, the stallion, and the mare, minimizing the risk of injury. Routine scanning and teasing of the mare are essential to confirm she will stand for service.
Sperm can remain viable in the mare’s reproductive tract for up to 72 hours, meaning ovulation must occur within this timeframe following service. Ideally, ovulation should happen within 48 hours after natural cover. To optimize this, your veterinarian can perform regular ultrasounds to monitor ovulation and examine the uterus for any inflammation or fluid post-breeding. The use of ovulation induction agents, such as Deslorelin (Ovuplant™ or Bio Release™ Deslorelin) or Chorulon™, can also help synchronize ovulation.
For mares that remain receptive to the stallion for extended periods within their cycle, owners may opt for repeated services. While routine scanning might be less frequent in such cases, it’s crucial to remember the importance of pregnancy diagnosis 14-16 days after the last service. Early detection of twins is vital, as there’s a small window between 14-17 days post-ovulation to safely reduce them, ensuring a single, viable pregnancy. The overall success of live cover breeding is inherently linked to the fertility of both the mare and the stallion. Studies have reported conception rates as high as 65% per cycle in intensively managed Thoroughbred mares in the Northern Hemisphere, with rates up to 70% achieved in Australia.
Chilled Semen Insemination: Expanding Genetic Access
Artificial insemination, particularly with chilled semen, presents numerous advantages. It allows breeders to utilize superior genetics from stallions located elsewhere, while their mare can be managed by a local veterinarian. This method reduces the need for transporting valuable livestock and minimizes risks to the mare during the breeding process.
Effective use of chilled semen requires intensive management of the mare by a veterinarian to maximize pregnancy chances. Ideally, mares should ovulate within 12-24 hours post-insemination. However, it’s important to consider that the semen was likely collected up to 24 hours prior to its arrival and has a limited lifespan. Coordinating mare ovulation, semen collection, and semen transportation can be complex, especially in remote areas. Despite these challenges, when managed appropriately, breeders can achieve pregnancy rates around 65% per cycle, comparable to live cover but with significantly reduced risk.
Frozen Semen Insemination: Overcoming Challenges with Advancements
Frozen semen has historically faced challenges due to issues with cryopreservation quality, post-thaw handling, and technician experience. However, significant advancements in ultrasonography, ovulation induction agents, improved cryopreservation methods, and quality control programs like Select Breeders Services (SBS) have substantially increased success rates.
Successful frozen semen insemination depends on mare and stallion factors, as well as technician expertise. Employing an experienced reproduction veterinarian is crucial for optimal mare management and timing of insemination. Generally, mares bred with frozen semen exhibit slightly lower first-cycle pregnancy rates (around 51.3%) compared to chilled semen (approximately 59.4%). However, some studies indicate that end-of-season pregnancy rates can be slightly better for frozen semen (75.6%) than chilled semen (74.7%).
Historically, more frequent ultrascans were needed for accurate timing with frozen semen. Now, timed insemination protocols and ovulation induction agents allow for management similar to chilled semen. It is important to note that not all mares are suitable for frozen semen insemination; older or “problem” mares may have lower pregnancy rates. In such cases, using a stallion with proven fertility via natural cover or chilled semen insemination is recommended.
References
- Morris, LHA, Allen, WR (2002) Reproductive efficiency of intensively managed Thoroughbred mares in Newmarket, Equine Veterinary Journal, 34: 51-60
- Bosh, KA (2006) Reproductive efficiency of thoroughbred mares in Central Kentucky, Journal of Equine Veterinary Science, 26:192-3
- Nath, LC, Anderson, GA, McKinnon, AO (2010) Reproductive efficiency of thoroughbreds and standardbred in North-East Victoria, Australian Veterinary Journal, 88: 169-175
- Squires, E.L, Barbacini, S., Matthews, P., Byers, W., Schwenzer, K. Steiner, J. and Loomis, P.R. (2003) Retrospective study of factors affecting fertility of fresh, chilled and frozen semen, Equine Veterinary Education, 18:2, 96-99
