Intra-uterine insemination with low numbers of frozen–thawed boar spermatozoa in spontaneous and induced ovulating sows under field conditions Kakanang Buranaamnuay ⁎, Padet Tummaruk, Mongkol Techakumphu Department of Obstetrics, Gynaecology and Reproduction, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand article info abstract Article history: Received 29 September 2009 Received in revised form 28 February 2010 Accepted 17 March 2010 The present study was conducted to evaluate non-return rate (NR), farrowing rate (FR), and number of total pigs born/litter (TB) of weaned sows after intra-uterine insemination (IUI) using low numbers of frozen–thawed (FT) spermatozoa. Semen from 6 boars was cryopreserved individually in a 0.5-ml straw, at a concentration of 1 × 10 9 spermatozoa/ml. A total of 40 multiparous sows with weaning-to-estrus interval of 3 to 7 days were included. The sows were detected for standing estrus twice daily and randomly assigned to two groups: I) spontaneous ovulation (n = 20) and II) induced ovulation (n = 20) which the sows were given 750 IU human chorionic gonadotrophin (hCG) i.m. immediately at estrus detection. Ovulation was determined every 12 h using transrectal ultrasonography. FT semen containing 1 × 10 9 motile spermatozoa/dose was used to IUI. In group I, the sows were inseminated at 24 h after the detection of estrus and repeated every 12 h until ovulation. In group II, the sows were inseminated at 36, 42 and/or 48 h after hCG treatment. The results showed that the interval from standing estrus to ovulation (EOI) differed significantly between group I (40.2 h) and group II (35.6 h; P = 0.01). Variation of EOI among sows within each group seemed to be lower in group II (4.5 h SD) than in group I (5.5 h SD; P = 0.5). The number of IUI per sow was 2.9 ± 0.6 times in group I and was 2.4 ± 0.5 times in group II. There were no significant differences (P N 0.05) in the NR (80 vs 85%), FR (60 vs 65%) and the TB (8.0±2.8 vs 9.4±3.7 piglets/litter) between the groups. These results indicated that multiple doses of IUI with a low number of FT boar spermatozoa provided a fairly good NR, and reasonable FR and TB both in spontaneous and induced ovulating sows. The number of inseminations required for attaining acceptable fertility tended to be lower in the weaned sows with induced ovulation. © 2010 Elsevier B.V. All rights reserved. Keywords: Frozen–thawed semen IUI Fertility hCG Sows 1. Introduction The procedure for artificial insemination (AI) in pigs using frozen–thawed (FT) semen involves the deposition of a high number of FT spermatozoa (5 to 6 × 10 9 cells) in a large volume of diluent (80 to 100 ml) into the cervix. Despite inseminating with this high sperm number, low fertility levels are usually obtained (about 20 to 30% conception (CR) and farrowing rates (FR) and 2 to 3 total piglets born/litter (TB) lower than those achieved by fresh semen) (Almlid and Hofmo, 1996; Johnson et al., 2000). Therefore, the use of FT semen in commercial AI swine herds is still limited (Wagner and Thibier, 2000). Recently, a procedure for non-surgical intra-uterine insemination (IUI) in sows, which allows the transcervical deposition of semen into the uterine body, has been developed (Sumransap et al., 2007; Watson and Behan, 2002). The fertility rates achieved by IUI with fresh semen using 1 × 10 9 spermatozoa/dose were comparable to those of conventional AI with 3 × 10 9 spermatozoa/dose (Watson and Behan, 2002). Furthermore, it has been demonstrated that the Livestock Science 131 (2010) 115–118 ⁎ Corresponding author. Tel.: + 66 1 2189644 5; fax: + 66 1 2520738. E-mail address: ningkakanang@yahoo.com (K. Buranaamnuay). 1871-1413/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2010.03.010 Contents lists available at ScienceDirect Livestock Science journal homepage: www.elsevier.com/locate/livsci