173
Effect of numbers of sperm and timing of a single, post- cervical insemination on fertility of weaned sows treated with OvuGel®
Variability in estrus and ovulation requires multiple inseminations during estrus to ensure one AI occurs close to ovulation. Induction of ovulation with a GnRH agonist after weaning improves synchrony of ovulation and allows for fixed time AI. However, the interaction between number of sperm in the AI dose and the timing of insemination have not been evaluated. The objective of this study was to determine the effects of sperm numbers in a single post cervical artificial insemination (PCAI) and the timing of insemination following induced ovulation in weaned sows. The experiment was performed in replicates at a 1000 sow, commercial research farm during summer and fall. Multiparous PIC sows (n = 503) were allotted by parity (average = 2.8) and lactation length (average = 19.3 d) to receive a single PCAI using 2.5 or 1.5 billion viable sperm at either 22, 26, or 30 h following OvuGel® administration at 96 h post-weaning. Sows received fence-line boar contact once daily 3 to 6 d following weaning. Sub-populations of sows (n = 427) were assessed for follicle size and ovulation utilizing ultrasound at 8 h intervals. Data were analyzed for the effects of sperm numbers and AI timing with and without ovarian follicle measures excluding sows that were diagnosed by trans- rectal ultrasound as having corpora lutea at time of ovulation induction. Of all sows, 89% expressed estrus within 6 d of weaning. At time of OvuGel® administration, >90% of sows had large (≥ 6.5 mm) follicles; with 89% of those ovulating by 48 h and 93% ovulating by 56 h. Pregnancy rate was not affected by replicate, lactation length, follicle size, or ovarian cysts, but was affected by parity, estrus expression and ovulation (P < 0.05). There was a tendency for number of sperm (P = 0.09) to affect pregnancy with AI using 2.5 billion (87%) greater than AI with 1.5 billion sperm (80%). Pregnancy rate following insemination at 22 h post-OvuGel® (89%) was greater (P = 0.03) than AI at 30 h (76%) while AI at 26 h (87%) did not differ. There was no interaction (P > 0.10) between number of sperm and timing of insemination. These preliminary data indicate that AI timing after ovulation induction affects pregnancy establishment and validates a recommended timing of insemination of 22 h following OvuGel®. Future farrowing and litter data will enable determination of optimal fixed AI timing and number of sperm.
Keywords: AI, fertility, ovulation, swine