The effect of exogenous melatonin administration before superovulation on embryo yield in Assaf ewes

The aim of this study was to determine the effect of exogenous melatonin administration on transferable embryos by increasing total antioxidant status before superovulation in Assaf ewes. Selected ewes were randomly divided into two equal groups: melatonin (n = 9) and control (n = 9). In the melatonin group, a melatonin implant (18 mg melatonin, Regulin®, Ceva, Turkey) was placed under the skin of the ear 7 days prior to insertion of the progesterone-containing sponge. In the control group, a physiological saline solution was injected under the skin of the ear on the same day. The same superovulation protocol was used in both groups. In addition, blood samples for determination of Glutathione peroxidase, superoxide dismutase, total antioxidant status and total oxidant status concentrations were collected on five different days, including the day of melatonin implant placement (Day-7), vaginal sponge insertion (Day 0), vaginal sponge removal (Day 11), mating (Day 12-13) and uterine flushing (Day 19). Embryos were collected by laparotomy on the 7th day after mating. Uterine flushing taken into petri dishes were scanned under a stereomicroscope, and the quality and developmental stages of the embryos were recorded. In the study, total corpus luteum count and total cell count were found to be higher in the control group than in the melatonin group (p < .05). When the results were evaluated in terms of oxidative stress index, a negative correlation was found between the total number of corpus luteum, number of cells obtained, count of transferable embryos and number of Grade 1 embryos on Day 0. There was also a positive correlation oxidative stress index and the number of unfertilized oocytes on Day-7. As a result, exogenous melatonin administration prior to superovulation during the breeding season is thought to have a negative effect on embryo yield and quality. Therefore, the use of exogenous melatonin in MOET studies during the breeding season is recommended to be investigated in new studies.

Towards Improving the Outcomes of Multiple Ovulation and Embryo Transfer in Sheep, with Particular Focus on Donor Superovulation

Considerable improvements in sheep multiple ovulation and embryo transfer (MOET)protocols have been made; however, unlike for cattle, MOET is poorly developed in sheep, and thus has not been broadly applicable as a routine procedure. The tightly folded nature of the ewe cervix, the inconsistent ovarian response to various superovulatory treatments, and the requirement of labor to handle animals, particularly during large-scale production, has limited the implementation of successful MOET in sheep. Moreover, several extrinsic factors (e.g., sources, the purity of gonadotrophins and their administration) and intrinsic factors (e.g., breed, age, nutrition, reproductive status) severely limit the practicability of MOET in sheep and other domestic animals. In this review, we summarize the effects of different superovulatory protocols, and their respective ovarian responses, in terms of ovulation rate, and embryo recovery and transfer. Furthermore, various strategies, such as inhibin immunization, conventional superovulation protocols, and melatonin implants for improving the ovarian response, are discussed in detail. Other reproductive techniques and their relative advantages and disadvantages, such as artificial insemination (AI), and donor embryo recovery and transfer to the recipient through different procedures, which must be taken into consideration for achieving satisfactory results during any MOET program in sheep, are also summarized in this article.

Transcervical vs. laparotomy embryo collection in ewes: The effectiveness and welfare implications of each technique

This study assessed animal welfare in ewes subjected to transcervical (TC) or laparotomy (LP) embryo collection, and the efficiency of these two techniques. Santa Inês ewes (n = 57) received a protocol for estrus synchronization and superovulation. Cervical dilation protocol was initiated 12 h before embryo collection in all ewes. Depending on the success of cervical passage, the embryos were collected from ewes by either TC or LP. Records were made of physiological (rectal temperature (RT) and heart rate (HR)), endocrine (cortisol concentration), biochemical (glycaemia, total proteins, globulin and albumin concentrations), and behavioral variables. Data were recorded before fasting (BF) and sedation (BS), during (DC) and immediately after embryo collection (IAC), and 1 h (1hAC), 3 h (3hAC), 6 h (6hAC), 12 h (12hAC), 24 h (24hAC), and 48 h (48hAC) after embryo collection. The LP and TC procedures were applied to 22 and 35 ewes (with 100.0% and 94.3% of procedures being successful, respectively). The use of LP took longer than TC (P = 0.007) but was less effective in the recovery of uterine fluid and structures (P = 0.0002 and P = 0.0180, respectively), with no difference in the number of viable embryos recovered per animal. The TC procedure induced a greater RT at DC (P = 0.002) and IAC moments (P < 0.0001). The heart rate was greater in TC than LP in IAC (P = 0.036). On the other hand, HR was greater with LP at 12hAC (P = 0.033) and 24hAC (P = 0.002). There was no interaction between the procedures and time on total proteins, albumin, or globulin concentrations. The TC procedure induced greater glycaemia than LP in IAC (P < 0.0001). LP induced greater serum cortisol concentration than TC at DC, IAC, 1hAC (P = 0.0004; P = 0.0006; P = 0.036, respectively), even though it was greater in the TC than the LP procedure at 3hAC (P = 0.008). In conclusion, the TC embryo collection was more effective than the traditional LP procedure. Although both embryo collection procedures affected ewes' welfare, the TC procedure is probably less stressor than the LP.

Successive in vivo embryo production in Santa Inês sheep

Context In vivo embryo production, also called multiple ovulation and embryo transfer, can accelerate genetic gain, and thus improve animal production. However, there are issues limiting a wider use of this biotechnology in sheep livestock. Aims This study aimed to determine (1) whether a previous response to superovulation (SOV) can be used as a criterion to select ewes for in vivo embryo production, (2) whether the intensity of the SOV response (number of corpora lutea, CL) can affect the embryo recovery rate, and (3) whether the number of CL quantified by colour Doppler ultrasonography can be used to calculate the recovery rate. Methods Twenty-five Santa Inês ewes underwent SOV three times (SOV1, SOV2 and SOV3), with 200 mg FSH and natural mating. The number of CL after each SOV was determined by laparoscopy and by colour Doppler ultrasonography. Key results The number of CL significantly decreased (P &lt; 0.05) after SOV1 (7.5 ± 4.8) to 3.0 ± 5.0 at SOV 2 and 2.2 ± 3.5 at SOV3. Strong correlations were observed between SOV2 and SOV3 in terms of numbers of CL (r = 0.86, r2 = 0.74; P &lt; 0.0001) and viable embryos (r = 0.79, r2 = 0.63; P &lt; 00001). However, no correlations were observed between SOV1 and SOV2 or between SOV1 and SOV3. Recovery rate did not differ with the intensity of the SOV response (≤6, 7–10, &gt;10 CL) or between the methods used to quantify CL. Conclusions Ewes did not show the same pattern of response when submitted to successive FSH-based SOV. The intensity of the SOV response did not affect the recovery rate, and the number of CL estimated by colour Doppler ultrasonography can be used to calculate the recovery rate. Implications Selecting sheep embryo donors by a previous SOV response is not always feasible. The recovery rate is homogeneous and it is not affected by the intensity of the SOV response. A nonsurgical technique can be used to assess the recovery rate, improving animal welfare in MOET programs.

Anti-Müllerian hormone and antral follicle count are more effective for selecting ewes with good potential for in vivo embryo production than the presence of FecGE mutation or eCG pre-selection tests

This study aims to compare four different methods for selecting high responding sheep donors for in vivo embryo production. These methods include a pre-selection eCG test (eCG), antral follicle count (AFC), plasma anti-Müllerian hormone measurement (AMH) and genotyping for the presence of the FecG^E mutation (a polymorphism in the GDF9 gene associated with increased ovulation rate). Santa Ines ewe lambs (n = 25) underwent superovulation (SOV) with 800 IU equine chorionic gonadotropin (eCG) and the corpus luteum (CL) count was recorded by laparoscopy after eight days. At the D0_eCG, blood samples for AMH and genotyping analysis were collected. Twenty-one days after the end of the eCG test, the same animals underwent SOV with 200 mg of FSH, administered in six decreasing doses, and then naturally mated. Immediately before the beginning of the FSH protocol (D0_FSH), and at the moment of the first FSH dose (D9_FSH), the AFC was assessed. Plasma AMH was again determined at the D9_FSH. After each screening process, animals were classified as having a high (HR), or low (LR), potential of response (using specific thresholds for each method). Then, the ewes' response to SOV and embryo yield for each screening method, classified as HR or LR, were compared. Animals classified as HR by AFC (HR_AFC) and by AMH concentration (HR_AMH) at the D9_FSH, produced more viable embryos than those classified as LR_AFC and LR_AMH (HR_AFC 6.2 ± 3.2 vs LR_AFC 2.8 ± 3.0 and HR_AMH 6.6 ± 3.6 vs LR_AMH 3.0 ± 2.9). Pre-selection tests with eCG and different FecG^E genotypes, either heterozygous (+/E) or wild type (+/+), were unable to discriminate HR or LR animals. A tendency (P = 0.06) to have lower plasma AMH was observed in heterozygous FecG^E (+/E) ewes. In conclusion, both AFC and plasma AMH can be used to select donor ewes with a higher potential of response for in vivo embryo production.