Intrauterine insemination of sows with reduced sperm numbers: results of a commercially based field trial.

Artificial insemination (AI) in pigs requires 2-3 billion spermatozoa to achieve consistently high fertility with current practice of inseminating into the posterior region of the cervix. We have investigated the potential advantages of inseminating through the cervix into the caudal region of the uterus using lower sperm numbers. Total sperm doses from 22 boars of 3, 2 or 1 billion spermatozoa were packaged in 80 ml volumes in X-Cell extender in gene-flat-pack (Cochette) bags. A novel inseminating device, the Deepgoldenpig, was employed which permits the ready introduction of a narrow catheter through the cervix into the uterus without traumatic injury to the mucosa. This was compared with the standard Goldenpig device that allows semen to be deposited in the posterior folds of the cervix. Sows of two different genotypes and of parities ranging from 2 to 11 were used. They were selected solely on the basis of a weaning to estrus interval of 4-6 days. Two inseminations, with a 24 h interval between them, were carried out on each sow. Pregnancy was determined at 35 days by ultrasound scan, and farrowing and litter size recorded. Pregnancy and farrowing data were very similar. The standard inseminating device produced farrowing rates of 91.1, 91.8 and 65.8% for insemination with 3, 2 and 1 billion spermatozoa, whereas the deep insemination device gave rates of 90.5, 90.5 and 86.9%. Only the 1 billion dose with the standard device was significantly different from the high dose control (P < 0.001). Similarly, the mean litter sizes with the standard device were 12.5, 12.6 and 10.3 and with the deep insemination device 12.3, 12.3 and 12.1. Only the 1 billion dose with the standard device was significantly lower (P < 0.001). None of the covariates differed significantly and there were no significant interactions with treatment. We conclude that transcervical insemination in the sow is simple, effective and safe, and allows the sperm dose to be reduced to 1 billion spermatozoa.