Collection of genital tract samples

All sows were subjected to mid-ventral laparotomies to collect the tissue samples 24 h after mating/inseminations (pre-/peri-ovulation period), as described by Alvarez-Rodriguez⁶. Briefly, sows were sedated by the i.m. administration of a mixture of 5 mg dexmeditomedine (Dexdomitor, Orion Pharma Animal Health, Sollentuna, Sweden) and 100 mg tiletamine hydrochloride/zolazepam hydrochloride (Zoletil vet, Virbac A/S, Kolding, Denmark) followed by anaesthesia induced i.v. with sodium thiopental (Abbot Scandinavia AB, Solna, Sweden, 7 mg/kg bw), and maintained with isoflurane (3.5–5%, Baxter Medical AB, Kista, Sweden) administered via a tracheal cuffed tube by a close-circuit PVC-ventilator (Servo ventilator 900 D, SIEMENS-ELEMA AB, Solna, Sweden). The number of pre-ovulatory follicles or eventual new ovulations per sow was 22.30 ± 7.29 (mean +− standard deviation) pre-ovulatory follicles, without significant differences between sow-groups. Peripheral blood was collected for estradiol 17ß (E₂) and progesterone ELISA analyses in plasma, which confirmed the animals were in pre-/peri-ovulatory estrus (mean ± SD pg/mL for P4 = 0.77 ± 0.35 in all sows; and for E₂ ranging 376.50 ± 27.76–294.20 ± 80.24 in all experimental groups, e.g., without significant differences). Segments of the female genital tract segments were immediately retrieved and stored at –80 °C in RNAlater (Ambion, Thermo Fisher Scientific Baltics UAB, Vilnius, Lithuania) until analysed.