Timing Protocol Modification for Frozen Semen Insemination in Mares

There are in use a variety of protocols for frozen semen insemination. This research compares the results from several currently used with those from a new timing protocol.

Protocol for frozen semen insemination - mare in stocksBackground:

  • There is a growing demand for use of frozen semen in equine artificial insemination practices
  • Classic protocols rely on time-intensive mare examination using post-ovulation insemination
  • Study goal: reduce examination frequency and eliminate the need for a second insemination

Study Design:

  • 67 mares (ages 3–22), 127 cycles across 3 years; multiple breeds
  • Ovulation induced (time = 0h) when criteria met: dilated cervix, uterine edema, follicle >35mm
  • Induction agents: hCG 3,000 IU IV, deslorelin acetate 1.7mg IM, or histrelin 0.5mg IM
  • Three protocols compared:
Protocol Examinations Insemination Timing
6 Hour Every 6h until ovulation At ovulation detection
Timed 24h, 30h, 48h 30h and 48h
Proposed 24h, 30h, 33–36h, 48h 33–36h (single dose)

Results:

  • Pregnancy rates per cycle: Proposed 69.2%, Timed 44%, 6 Hour 48.6%
  • No statistically significant difference between groups

Conclusions:

  • Proposed protocol achieves comparable pregnancy rates using a single frozen semen dose
  • Eliminates examinations between 10PM–8AM, directly improving clinician wellbeing
  • Limitations: retrospective design; small Proposed group sample size (9 mares, 13 cycles)

(Hayna J, Ragon A, Hubner A. 2025. Protocol modification for frozen semen insemination in mares. JEVS 145:105292. JEVS 145:105277 – Presented in Association with and by Permission of the International Society for Equine Reproduction)