Changes on corpus luteum structure and progesterone synthesis pathway after hCG or GnRH treatment during the early luteal phase in sheep.

This study investigated the effect of hCG or GnRH on structural changes of the corpora lutea (CL) and the regulation of the expression of steroidogenic enzymes involved in P4 secretion in post-ovulatory (po-CL) and accessory CL (acc-CL). Sixty-four ewes were assigned to three groups receiving: 300 IU of hCG (hCG) or 4 µg Buserelin (GnRH) or 1 mL of saline solution (Control) on Day (d) 4 post artificial insemination (FTAI). Laparoscopic ovarian were performed on d 4, 14 and, 21 post-FTAI to determine the numbers of CL. Blood samples were collected for serum LH and P4 analysis. On d 14 post-FTAI, both CL were removed from the ovary to determine large luteal cell (LLC) number and to evaluate the expression of steroidogenic enzymes (HSD3B1, STAR, CYP11A1). Only hCG and GnRH treated ewes generated acc-CL. The LLC in both po- and acc-CL were significantly greater in the hCG group compared to GnRH and Control groups (P<0.05). Overall, hCG group showed the greatest immunodetection of HSD3B1and STAR in both po- and acc-CL (P<0.05). rnRNA expression of HSD3B1, STAR and CYP11A1 in the acc-CL tended to be greater in hCG group than in GnRH group (P<0.1). The LH concentration was increased in GnRH group (P<0.05) and P4 concentration was greater in hCG group compared to the other groups (P<0.05). In conclusion, administration of hCG has a notably impact on acc-CL development and the expression of steroidogenic enzymes compared to GnRH treatment in ewes. This leads to elevated P4 concentration and improved luteal function.

A simple method to select high superovulatory responder goats.

In most female mammals, a common drawback to multiple ovulation embryo transfer programs is the variability in the superovulatory response to the multidose pFSH treatment. The aim of the present study was to identify embryo donor goats based on their response to superovulation before the performance of a high-cost hormonal treatment, as we have previously done in sheep. To this end, we evaluated the number of ovulations obtained in response to the administration of a one-shot eCG treatment and related it with the subsequent ovarian response to a multiple-dose pFSH treatment in 33 goats of the Criolla-Neuquina breed. Goats received a one-shot eCG treatment of 800 IU at the end of a 17-day progestational treatment; 9 days later, started a second 17-day progestational treatment and then received a multiple-dose pFSH treatment on days 15-17 (116 mg pFSH, in six decreasing doses). The number of corpora lutea (CL) per goat was recorded laparoscopically after both hormonal treatments. On day 8 after the second pessary removal, embryos were surgically recovered and classified by quality. Results showed a significant positive correlation between the number of CL obtained in response to the eCG and pFSH treatments (r = 0.41; y = 0.8352x + 6.9906; P < 0.05), although of limited value to select high ovulatory responding goats, due to its low correlation value. Then, goats were grouped into high and low ovulatory responders to the eCG (High ≥9; Low <9 CL) and pFSH treatments (High ≥13; Low <13 CL). After the eCG and pFSH treatments, 60% of the goats maintained their classification as high or low superovulatory responders (expressed as recurrence rate). Significant differences were found in the number of CL (18.2 ± 1.3 vs 9.9 ± 1.3), number of embryos + oocytes (13.5 ± 1.7 vs 7.6 ± 1.7), number of embryos (10.8 ± 1.4 vs 5.1 ± 1.4) and number of Grade 1 and Grade 2 embryos (8.8 ± 1.4 vs 4.3 ± 1.4) between high and low superovulatory responder goats (P < 0.05), while no differences were observed in the number of oocytes and in the recovery of embryos + oocytes, embryos, Grade 1 and Grade 2 embryos and fertilization rates (P > 0.05). In conclusion, the recurrence rate in ovarian response between the one-shot eCG treatment and the multiple-dose pFSH treatment would confirm the existence of an "individual or intrinsic factor" of the donor goat that would respond as a high or low ovulatory responder to superovulatory treatments.

A successful vitrification technique for goat morulae conservation.

The aim of this study was to evaluate the effect of different vitrification and warming processes on the in vitro embryo survival of caprine morulae, considering the day of recovery. A total of 136 morulae of Criolla-Neuquina goats recovered on Days 7 or 8 after sponge removal, were exposed to three different vitrification processes; V1 (n = 48): glycerol (G) + ethylene glycol (EG); V2 (n = 44): EG + 0.5 M sucrose and V3 (n = 44): G + EG + 0.5 M sucrose. The morulae of each vitrification process were randomly assigned to three warming processes; W1 (n = 45): 0.5 M sucrose at 25 °C; W2 (n = 44): 0.5 M sucrose at 39 °C; and W3 (n = 47): solution containing half the concentration of the cryoprotectants + 0.5 M sucrose at 25 °C. After, embryos were cultured in 100 µL TCM 199 drops under mineral oil, at 39 °C and a 6.5% CO2 atmosphere for 72 h according to the different treatments. There were no viable embryos in V1 and V2 in none of their three respective warmings. Only V3 showed an embryo survival rate to hatched blastocyst stage of 59.1%. When considering embryo survival according to the warming processes, the survival rate was higher in V3W2 (76.9%) and V3W3 (66.7%) groups compared to the V3W1 group (37.5%; P < 0.05). The embryo survival of V3 for Day 8 after sponge removal (81.3%) was higher compared to Day 7 (46.4%; P < 0.05). In conclusion, a successful embryo survival is obtained by using a combination of cryoprotectants (G + EG) with addition of sucrose in the vitrification process for conservation of caprine morulae in embryo transfer programs. The survival rates in vitro of vitrified-warmed morulae in goats were influenced by their recovery day. Further studies should be conducted to determine if these results are reproducible in vivo embryo transfer on field situations.

Technical recommendations for artificial insemination in sheep.

Artificial insemination (AI) was the first important biotechnology applied to improve the genetics of farm animals. It allows the rapid and massive diffusion of desirable characteristics of males with high productive potential. We describe the different types of estrus induction and synchronization techniques and the use of the AI with fresh, chilled or frozen semen. Through the adequacy of the protocols of estrus synchronization and AI to the different production systems, the efficient use of reproductive techniques is possible, reaching acceptable pregnancy rates. Summary of reproductive results obtained using cervical and laparoscopic AI are presented.