Short Communication IXth International Conference on Boar Semen Preservation 2019

Effects of number of sperm and site of uterine semen deposition on conception rate and number of embryos in weaned sows receiving a single fixed time insemination (#7.2)

Robert Knox 1 , Brad Belstra 2 , Kilby Willenburg 2 , Domingo Gomez 2 , Kara Stewart 3
  1. University of Illinois, Champaign, IL, United States
  2. Fast Genetics, DeForest, WI, USA
  3. Animal Sciences, Purdue University, West Lafayette, IN, USA

Reducing the number of sperm required to produce a litter can allow superior boars, of higher genetic merit, to influence more pigs. Induced ovulation and a single fixed time artificial insemination (SFTAI), combined with uterine (UI) or deep uterine insemination (DUI), could help improve fertility with low numbers of sperm. The primary objectives were to determine the fertility effects of sperm numbers and site of insemination. The study was performed on 7 wean groups on a 3,600-sow commercial farm. At weaning (0 h), sows (n=534) were assigned by parity and estrus induction method (eCG or none) to receive 1.2 x 109 sperm by UI, 0.6, 0.3, or 0.15 x 109 sperm by UI or DUI, or 0.075 x 109 sperm by DUI. At 80 h after weaning, all sows received OvuGel and 26 h later a SFTAI using pooled semen. Sows were exposed to boars once daily and ultrasound was performed to determine follicle size and time of ovulation. At 4 wks post-SFTAI, sows were slaughtered to determine pregnancy status, numbers of corpora lutea (CL), and embryos. Data were analyzed using 3 levels of sperm (0.6 to 0.15) and 2 levels for site (UI vs DUI) to test for interactions, and then for the overall effects of AI method (8 treatments). Other variables included parity, AI-to-ovulation interval, and number of CL. Sows averaged parity 3.7, and weaned 10.4 pigs after lactating for ~19 d. Overall expression of estrus was 93% within 5 d of weaning with an average wean-to-estrus interval of 3.9 d. Average follicle size was 6.1 mm at OvuGel and the interval from AI-to-ovulation was 16.4 h. Pregnancy rate averaged 78.6%, number of CL 21.7, and number of normal embryos 12.2. There was no effect of site of insemination and no interaction with the number of sperm. Pregnancy rate (range: 80.9% to 70.5%) was not affected by number of sperm but was influenced by interval from AI-to-ovulation (P < 0.02) with AI after ovulation dramatically reducing rate. Number of embryos (range: 16.5 to 10.3) was affected by AI treatment (P < 0.0001) with more embryos present with higher numbers of sperm (1.2 and 0.6) compared to lower numbers of sperm (0.3 to 0.075). Numbers of total and healthy embryos increased with number of CL (P < 0.0001). These results suggest that litter size is more sensitive to low sperm numbers than pregnancy status and DUI is unable to compensate for lowering the number of sperm. Acceptable fertility can be achieved with low numbers of sperm when using a SFTAI and uterine deposition, but both insemination to ovulation interval and ovulation rate influenced final fertility.