54 Altrenogest supplementation during early pregnancy improves swine embryonic development

Progesterone (P4) is of paramount importance in the establishment and maintenance of pregnancy for mammals. Progesterone stimulates the endometrial secretion of several molecules involved in conceptus growth and development during the peri-implantation period. Indeed, several studies involving ruminants have reported that exogenous P4 supplementation is related to increased early embryo development, higher levels of interferon tau, and improved pregnancy rate. However, there is a lack of information about P4 supplementation during early pregnancy regarding swine embryonic development. Additionally, some of the few studies involving pigs have shown an impaired pregnancy rate when supplementation was performed before Day 6 of pregnancy. Thus, the objective of this study was to evaluate the effects of progesterone/progestin supplementation from Day 6 of pregnancy on total number of embryos (TE), pregnancy rate (PR), embryo development, and maternal serum 17β-oestradiol concentration (17β-E). A total of 31 crossbred, 2 to 6 parity sows were used. All sows were inseminated every 24 h through the first oestrus following a 21-day lactation, and ovulation was detected by transrectal real-time ultrasound to determine Day 0 of pregnancy. On Day 6 of pregnancy, animals were randomly allocated to one of the following groups: CON (n = 11), non-supplemented sows; RU (n = 11), sows supplemented daily with 20 mg of Altrenogest-Regumate® from Day 6 to 12 of pregnancy; and PG (n = 9), sows supplemented with 2.15 mg/kg of long-acting P4 IM on Day 6 of pregnancy. Sows were treated with altrenogest p.o. as a top dressing over a small portion of feed. Blood samples were collected from 12 sows (4 per group) on Day 12 of pregnancy to measure the level of plasma 17β-E by radioimmunoassay. Sows were slaughtered on Day 28 of pregnancy. The uterus from each sow was collected and embryos were counted to determine TE. Embryos were individually separated from their placentas, weighed, and crown-to-rump length was determined. Data were analysed by the SAS program. All variables were analysed by PROC-MIXED t-test. Statistical difference was considered when P   0.05). No difference was observed among groups for TE and 17β-E level (P > 0.05). However, embryonic weight and crown-to-rump length differed among the 3 groups (P < 0.001). The RU-treated sows had heavier and bigger embryos when compared with the other groups. In contrast, PG-treated sows had the lowest averages for the same variables (weight: 1.39 ± 0.01, 1.46 ± 0.02, and 1.22 ± 0.01; crown-to-rump: 21.07 ± 0.08, 21.61 ± 0.11, and 20.66 ± 0.11; for CON, RU, and PG, respectively). In conclusion, altrenogest supplementation from Day 6 to 12 of pregnancy increases size and weight of porcine embryos, whereas 2.15 mg kg−1 of long-acting P4 on Day 6 of pregnancy decreased these variables when compared with non-supplemented sows. Research was supported by FAPESP Grant 2017/00290-0.