Retrospective study of factors affecting fertility of fresh, cooled and frozen semen

A retrospective study of artificial insemination of 251 mares using chilled and fixed time frozen‐thawed semen

“…This study used a fixed time procedure that involved using 2 doses of frozen semen per cycle, which, combined with the use of a reliable ovulatory agent, considerably reduced the management required to achieve successful pregnancy rates. The study supports the report of Squires et al (2006) that mares can be inseminated more than once during a cycle with frozen semen without a decrease in fertility. Hemberg et al (2006) used just one insemination dose post ovulation (first cycle pregnancy rate 45.4%); however this considerably increases the veterinary input to ensure the deposition of the semen at the time of ovulation.…”

“…This study disproves the stated hypothesis that artificial insemination with chilled semen achieves higher conception rates than using frozen semen, supporting previous reports (Loomis 2001;Squires et al 2006). This result is of considerable clinical significance as it contradicts the preconceptions of many mare owners and veterinary surgeons that frozen semen produces poor conception rates.…”

“…Reger et al (2003) reported seasonal pregnancy rates of 86.6% and per cycle pregnancy rates of 76.4% using frozen semen, but only based on 30 mares in the frozen semen group and used hCG as its induction agent. Squires et al (2006) reported a per cycle conception rate of 46% over 2 breeding seasons from 536 mares using frozen semen, and per cycle conception rate of 44% over 2 breeding seasons from 272 mares using chilled semen with the induction agent of choice being hCG.…”

“…Previous reports have included: Squires et al (2006) in a series of 536 frozen semen inseminations using various insemination strategies with a 46% per cycle pregnancy rate; Samper et al (2002) a rate of 40%, inseminated in a commercial setting with frozen semen from various sources; Loomis (2001) one cycle pregnancy rates for mares with cooled (59%) and frozen (51%) semen in a commercial setting; and Reger et al (2003) described a clinical trial with mares being inseminated twice at 24 and 40 h after HCG injection with a per cycle pregnancy rate of 76.4% (26 pregnancies out of 34 cycles) and seasonal pregnancy rate of 86.6%.…”

“…Historically, several factors have limited the use of frozen semen in the commercial setting, the foremost being the increased frequency of ultrasound examinations to determine the appropriate timing of insemination (Squires et al 2006). In order to achieve the highest fertility rate, frozen semen must be inseminated between 12 h pre-and 6 h post ovulation (Barbacini et al 1999;Sieme et al 2003).…”