Preserving sperm quality during transport is paramount to equine breeding success. This principle applies whether using a fresh, cooled, or frozen sample. At the 2025 Cavalcade Education Equine Reproduction Seminar, held in Red Hook, New York,  Jan. 8, Alana King, DVM, Dipl. ACT, of Millbrook Equine Veterinary Clinic, in New York, shared the latest guidelines for the successful collection and transport of fresh, cooled semen.

Semen Collection Process in Horses

Obtaining semen for artificial insemination (AI) involves the stallion mounting a phantom mare or dummy, with the penis diverted into an artificial vagina (AV) to collect the semen. The AV setup is one of the most critical factors in successful semen collection. King highlighted the importance of adjusting the device’s internal temperature, pressure, and lubrication to each stallion’s preference. She recommended carefully recording the AV setup for each stallion to replicate it consistently.

Wash the stallion’s penis and sanitize equipment thoroughly to remove dirt and debris that could introduce bacteria and negatively impact semen quality. Along with a reliable teaser mare, King stressed the importance of having an experienced stallion handler present to ensure everyone’s safety.

Evaluating Equine Semen for Fertility

After collecting the semen sample, veterinarians evaluate it both grossly and under a microscope for quality—which translates to fertility—and pair it with an extender. King described the steps to measure volume, concentration, and total sperm count, noting these parameters can vary widely between stallions, but the total sperm count is the most important factor in determining fertility. “This number is generally 8 (billion) to 10 billion sperm per ejaculate, 1 (billion) to 2 billion of which is shipped to each mare,” she said.

Beyond sperm count, King also described the role of motility in assessing semen quality. “Progressive motility (sperm swimming in mostly straight lines or large circles) is a better predictor of fertility than total motility, because the latter counts sperm that move erratically without the ability to travel to and fertilize an egg.”

Role of Extenders in Horse Semen Transport

Semen extenders are specifically formulated preservative solutions that allow cooled sperm to survive transport and remain viable long enough for the mare to be artificially inseminated on arrival. King recommended conducting extender trials to determine the best option for each stallion because individuals’ semen can react differently to the antibiotics often contained in these extenders.

Maximizing Horse Semen Quality

To maximize semen fertility potential, King recommended:

• Before collecting semen for insemination, conduct clean-out ejaculations to avoid sperm degradation that can occur when semen is held in the epididymis for too long.
• Ensure proper lighting in the stallion’s stall to support optimal sperm production. Horses are long-day breeders (animals with reproductive cycles stimulated by an increase in daylight length).
• Consider supplements such as the antioxidant alpha (α)-lipoic acid and omega-3 fatty acids to improve sperm quality and motility.
• Centrifuge samples to remove seminal fluid that can be detrimental to stored semen.

Take-Home Message

With AI in horses, every extra step and hour lapsed between ejaculation and insemination has the potential to degrade semen quality. With the proper knowledge, equipment, and attention to detail, breeders can work alongside their veterinarians to consistently produce high-quality semen samples that maximize the chances of a successful conception, said King.