Rectally Guided or Hysteroscopic Insemination: Is there a difference?

The increasing use of frozen semen, the high cost of a dose of semen from some stallions, and the inability of some stallions to cope with their demand has triggered an incentive to reduce the number of spermatozoa from the traditional 500 PMS to significantly lower numbers per insemination. Two techniques have been described to deposit low sperm numbers in the uterus. Although experimental results have been reported for the rectally guided deep horn insemination (RGDHI) and endoscopic deep horn insemination (EDHI) techniques, little information is available in clinical settings with respect to the results of either method. This article reports on a comparison of the rectally guided insemination and hysteroscopic techniques in a clinical setting over three breeding seasons. Semen frozen in 0.5-mL straws and concentrations of 40 to 200 million per straw was available from 88 stallions whose fertility with frozen semen ranged between 0% and 100%. Of the 2544 inseminations performed 1279 were done by RGDHI, which resulted in a 43% seasonal pregnancy rate compared with 45% for the 1265 inseminations using the EDHI technique. There was an overall, but nonsignificant, advantage for the EDHI technique over the RGDHI and semen usage was slightly lower when using the EDHI procedure. There was no difference in fertility among breeding seasons for either technique. However, fertility of some stallions was increased by increasing the sperm numbers in the inseminates. From these data and results from others, it is evident that lower sperm numbers deposited by rectally guiding a flexible pipette to the tip of the horn or by using an endoscope to deliver the semen will result in acceptable pregnancy rates with frozen semen in commercial settings.