Techniques for the insemination of low doses of stallion sperm

In the last decade, there has been a significant increase in the quality and commercial use of frozen equine semen. The emergence of new reproductive technologies, coupled with the high prices for an insemination dose from some stallions, the increasing costs of import and export and the marketing policies of stallion agents or owners in the sport horse industry has stimulated the fractionation of doses for insemination. Consequently, the sperm number and the volume of an insemination dose are significantly reduced. To deliver lower doses of sperm in lower volumes compared to the standard dose, two techniques are used in clinical practice. Semen can be delivered hysteroscopically (HI) or by rectally guiding a flexible pipette to the tip of the desired uterine horn (RI). Both techniques have been described with good success and have triggered an incentive to further reduce the number of spermatozoa without having a negative effect on fertility. This article will review the expected success of both techniques in clinical settings and will highlight their advantages and disadvantages both for the mare and stallion. In addition, some of the implications of reducing sperm numbers on the industry will be discussed. From the available information, it is evident that lower sperm numbers deposited by RI or HI to deliver the inseminate can result in acceptable pregnancy rates with fresh or frozen semen in commercial settings. These methods of insemination could have major implications in the implementation and commercialization of new and emerging technologies in the equine industry.