A total of 411 mixed-parity sows were subjected to controlled ovulation by injection of 600 IU equine chorionic gonadotrophin at weaning and 5 mg porcine luteinizing hormone (pLH) 80 hours later. Sows were assigned to a single insemination of 1 or 3 × 109 sperm delivered into either the cervix or uterus. Inseminations were performed
approximately 36 hours after pLH injection. Intensity of standing estrus at insemination was subjectively scored as 1
to 3, with 3 being a stronger response, and semen backflow was recorded as yes or no. Number of sperm and site of
deposition did not affect pregnancy or farrowing rates or subsequent litter size. Mean farrowing rates were 68.32% and 68.63% in sows inseminated using an intrauterine catheter and either 1 or 3 × 109 sperm, respectively. In sows inseminated using the cervical method, farrowing rates were 77.88% and 67.31% when 1 and 3 × 109 sperm were used, respectively. Greater intensity of estrus at insemination was associated with higher pregnancy and farrowing
rates (P < .001), and backflow during insemination was associated with lower pregnancy and farrowing rates (P <
.01). When appropriately timed after induced ovulation, insemination of low sperm numbers does not adversely affect sow fertility, and this lack of effect is independent of the site of sperm deposition.