Effects of different artificial insemination techniques and sperm doses on fertility of normal mares and mares with abnormal reproductive history.

The research involved studying the effects of various artificial insemination (AI) techniques and sperm doses on the fertility of normal Hanoverian breed mares and those with a history of barrenness or pregnancy failure. The results indicated that the type of semen, breeding mares during foal heat, as well as the interaction between insemination technique, semen parameters, and mares, had substantial impacts on fertility.

Research Design and Methods

• The study analyzed 187 mares classified as normal (148 foaling and 39 young maiden mares), and 85 labeled as ‘problem mares’ with a history of reproductive issues like barrenness or pregnancy failure.
• The mares were randomly distributed into groups based on factors including AI technique (routine AI into the uterine body, transrectally controlled deep intracornual AI ipsilateral to the preovulatory follicle, or hysteroscopic AI onto the uterotubal junction ipsilateral to the preovulatory follicle), storage method of semen (fresh, frozen-thawed), AI volume (0.5, 2, 12 ml), and sperm dose.
• Factors like insemination technique, mare, semen, and stallion were examined using multivariate logistic models to establish expectation values and confidence intervals. The differences in pregnancy rates among the varying treatment groups were analyzed through a Chi-squared test.

Key Findings

• The study found that neither AI technique, volume, sperm dose, mare, nor stallion had significant effects on fertility (P > 0.05).
• However, factors like the type of semen, breeding mares during foal heat, and an interaction between AI technique, semen parameters, and mares did have significant impacts (P < 0.05).
• For ‘problem’ mares, the use of frozen semen during AI resulted in considerably lower pregnancy rates than those relying on fresh semen. But, such a difference was not observed among ‘normal’ mares.
• Among ‘normal’ mares, hysteroscopic AI with fresh semen yielded significantly better pregnancy outcomes than uterine body AI. On the other hand, ‘problem’ mares experienced significantly lower pregnancy rates with hysteroscopic AI compared to uterine body AI.
• Ultimately, the findings suggest that for mares with reproductive issues, conventional insemination into the uterine body proves superior to hysteroscopic insemination. Conversely, for normal mares, the highest pregnancy rates can be expected through hysteroscopic insemination.