Low-dose insemination-Why, when and how

The typical dose for insemination into the uterine body of the mare is >300 × 106 progressively motile spermatozoa (PMS) and an insemination dose of >200 × 106 PMS is recommended for frozen-thawed semen. Low-dose insemination techniques allow for a drastic reduction in the numbers of spermatozoa required to achieve pregnancy. Acceptable pregnancy rates can be achieved with doses ranging from 1 to 25 × 106 PMS in volumes ranging from 20 to 1000 μL. Two techniques have been described: hysteroscopic insemination and transrectally guided deep horn insemination using a pipette. Similar pregnancy rates can be attained by either method when 5 × 106 PMS are used. Hysteroscopic insemination may provide an advantage when the dose is 1-3 × 106 PMS. These techniques have the potential to make more efficient use of frozen-thawed or sex-sorted semen from certain stallions. The use of low-dose insemination to improve fertility of infertile stallions warrants further investigation.