Sheep estrous synchronization is mainly based on progestagen-impregnated sponges which could cause vaginitis. Several species of Lactobacillus used as probiotics are commonly used in the treatment or prevention of urogenital infections in humans. However, no studies have been performed to analyze the potential use of probiotics to prevent urogenital infections in sheep. A randomized controlled clinical trial was conducted with 21 one-year-old ewes to develop a model of probiotic infusion in vaginal sponges in order to study their influence in ewe’s vaginal microbiota, general health status, fertility and prolificity. Synchronization of estrus was based on intravaginal sponges for 14 days. Bacterial communities (Enterobacteriaceae and lactic acid bacteria) were highly fluctuating over time and between animals. The safety of probiotic infusion (mix of Lactobacillus spp. 60% L. crispatus, 20% L. brevis and 20% L. gasseri) in the vagina of healthy ewes was firstly confirmed. Neutrophils were observed in 80% (8/10) of the control ewes compared to 36% (4/11) of the ewes in the probiotic group 2 days after sponge removal (p = 0.056). Fertility in the control and probiotic groups was 60% (6/10) and 91% (10/11), respectively p = 0.097. These results suggest that Lactobacillus spp. infusion in the ewe’s vagina does not affect general health status or fertility.

Excellent fertility and prolificacy have been reported after non-surgical deep uterine transfers of fresh in vivo-derived porcine embryos. Unfortunately, when this technology is used with vitrified embryos, the reproductive performance of recipients is low. For this reason and because the embryos must be stored until they are transferred to the recipient farms, we evaluated the potential application of non-surgical deep uterine transfers with in vivo-derived morulae cultured for 24 h in liquid stage. In Experiment 1, two temperatures (25°C and 37°C) and two media (one fully defined and one semi-defined) were assessed. Morulae cultured in culture medium supplemented with bovine serum albumin and fetal calf serum at 38.5°C in 5% CO₂ in air were used as controls. Irrespective of medium, the embryo viability after 24 h of culture was negatively affected (P<0.05) at 25°C but not at 37°C compared with the controls. Embryo development was delayed in all experimental groups compared with the control group (P<0.001). Most of the embryos (95.7%) cultured at 37°C achieved the full or expanded blastocyst stage, and unlike the controls, none of them hatched at the end of culture. In Experiment 2, 785 morulae were cultured in the defined medium at 37°C for 24 h, and the resulting blastocysts were transferred to the recipients (n = 24). Uncultured embryos collected at the blastocyst stage (n = 750) were directly transferred to the recipients and used as controls (n = 25). No differences in farrowing rates (91.7% and 92.0%) or litter sizes (9.0±0.6 and 9.4±0.8) were observed between the groups. This study demonstrated, for the first time, that high reproductive performance can be achieved after non-surgical deep uterine transfers with short-term cultured morulae in a defined medium, which opens new possibilities for the sanitary, safe national and international trade of porcine embryos and the commercial use of embryo transfer in pigs.