Reproductive season affects inhibitory effects from large follicles on the response to superovulatory FSH treatments in ewes

Plasma steroid profiles and ovarian response in llamas treated with eCG for superovulation combined with exogenous progesterone during early luteal phase

The objective of this study was to evaluate the effects of plasma progesterone (P₄) concentrations during eCG-ovarian follicular superstimulatory treatment performed in early luteal phase and estradiol concentrations during peri-ovulatory period on ovarian response, number and embryo quality. On Day -2, females (n = 75) having a follicle ≥7 mm were treated with GnRH to induce ovulation. On Day 0, females that had ovulations (n = 54) were treated with 1000 IU eCG and were assigned to one of two treatments: (1) intravaginal device (ID) containing 0.5 g P₄ (P₄ group) and (2) no ID (Control group). On Day 5, females were administered PGF_2α and the ID was removed. On Day 7 and 8, females were mated and embryo recovery was performed 7 or 8 days later. Blood samples were collected from Day 0 to 9. Number (± SD) of follicles ≥7 mm on day of mating was greater (P =  0.04) in the control (9.7 ± 4.2) than P₄-treated (6.7 ± 4.9) group; number of corpora lutea did not differ (5.5 ± 3.1 and 5.2 ± 3.4 respectively). Ovulation rate was greater (P <  0.01) in the P₄-group (77.4%; 130/168) than control group (53.3%; 135/253). Number of embryos with an excellent grade (grade 1) tended to be greater (P =  0.07) in the P₄-group (82.4%; 42/51) than control group (65.4%; 36/55). It was concluded that supplementation with exogenous P₄ during eCG treatment in early luteal phase inhibits excessive follicular growth, increases ovulation rate and improves embryo quality.

Artificial insemination in Payoya goats: factors affecting fertility

The present study was conducted to determine the effect of different factors on pregnancy rate after artificial insemination (AI) with refrigerated and frozen semen in Payoya goats reared under commercial farm conditions. A total of 820 goats, belonging to 10 farms, was used. The total number of studied inseminations was 1384 over a 4-year period. Factors considered in the study were year, farm, month of AI, age of the goat at AI, dose of progestagen, eCG dose, buck, type of semen (refrigerated or frozen), technician, number of goats to be inseminated (group size), incidences at AI (problems, no problems, trans-cervical insemination), distance from semen collection to farm, number of previous kidding, kidding–AI interval, and milk production. The variable studied was fertility, expressed as successful kidding. Mean fertility was 59%. Six (farm, age, group size, transcervical AI, number of kidding and milk production) of the 15 factors studied presented a significant (P < 0.05) effect on fertility after AI. Our results demonstrated that it is difficult to control all the critical aspects of AI programs at the farm level. These factors should be controlled and the variations that could compromise the chance of being pregnant must be known by technicians. The good fertility results obtained during the non-breeding season emphasise the implementation of this technique so as to improve the competitiveness of the dairy Payoya breed flocks.

New approaches to superovulation and embryo transfer in small ruminants

The present paper reviews the current state of knowledge in multiple ovulation and embryo transfer (MOET) technology in small ruminants, focusing on recently reported information. Major new findings are related to follicular wave patterns in small ruminants, the elucidation of follicular dominance and the integration of this information into ovarian superstimulatory treatment protocols. Follicular dynamics determine steroid and gonadotrophin secretion, follicular responses to FSH, ovulatory responses and embryo yield. Protocols that control follicular dominance have been designed to allow the initiation of superstimulation at the beginning of a follicular wave. New approaches consist of (1) synchronisation of ovulation for superstimulation during Wave 1 (i.e. Day 0 protocol), (2) pretreatment with a gonadotrophin-releasing hormone (GnRH) antagonist from 10 days prior to FSH treatment to avoid follicular dominance and (3) progesterone–oestradiol cotreatment to synchronise follicle wave emergence. These protocols provide a homogeneous pool of small follicles that are gonadotrophin responsive, enhancing the superovulatory response and embryo yield with a reduction in the incidence of unovulated follicles and early regression of corpora lutea. In addition, the rate of fertilisation failure has been reduced by using an inducer of ovulation (i.e. GnRH) associated with intrauterine insemination. In summary, the application of recently acquired knowledge has resulted in relevant improvements in MOET programmes in small ruminants.

Progesterone treatment, FSH plus eCG, GnRH administration, and Day 0 Protocol for MOET programs in sheep

The effect of various superstimulatory treatments on the number of corpora lutea, fertilization rate, and embryo yield was studied in sheep. Overall, data from 708 Merino donors and 4262 embryos were analyzed in four experiments. In Experiment 1, varying intervals of progesterone treatment (5 to 14 d) before follicle-stimulating hormone (FSH) administration did not significantly affect the proportion of responding donors, the mean number of corpora lutea, or the mean number of recovered and transferable embryos per donor. In Experiment 2, a single dose of equine chorionic gonadotropin (eCG, 200 or 300 IU) combined with the FSH treatment (i.e., given at CIDR removal) reduced the number and the quality of embryos compared with that for not giving eCG (P<0.05). In Experiment 3, one dose of gonadotropin-releasing hormone (GnRH) given 24h after CIDR removal improved the number of transferable embryos compared with that for not giving GnRH (P<0.05). In Experiment 4, the new superstimulatory Day 0 Protocol, which includes starting FSH treatment at the emergence of Wave 1 (i.e., soon after ovulation, in the absence of a large follicle), improved ovarian response, with a tendency to produce more embryos compared with that for the Traditional Protocol. In summary, this study, analyzing data from various pharmacologic treatments, allows an improvement from four to eight transferable embryos per treated donor in multiple ovulation and embryo transfer programs in sheep.

Undernutrition and exogenous melatonin can affect the in vitro developmental competence of ovine oocytes on a seasonal basis

This study evaluated the effects of exogenous melatonin and level of nutrition on oocyte competence, in vitro fertilization (IVF), and early embryonic development in sheep during seasonal anoestrus (SA) and the reproductive season (RS). Adult Rasa Aragonesa ewes were assigned randomly to one of four treatment groups in two experiments based on a 2 x 2 x 2 factorial design. Individuals were treated (+MEL) or not treated (-MEL) with a subcutaneous implant of melatonin for 42 days and then were fed 1.5 (Control, C) or 0.5 (Low, L) times the daily maintenance requirements for 20 days. Ewes were synchronized and mated at oestrus (Day = 0). On Day 5, ovaries were collected and oocytes were used for IVF. Season had a significant (p < 0.01) effect on the number of oocytes recovered (RS: 19.6 +/- 1.0; SA: 14.5 +/- 1.0) and the number of healthy oocytes (RS: 13.9 +/- 0.7; SA: 9.0 +/- 0.7). In the RS, neither nutrition nor melatonin had a significant effect on the evaluated oocytes quality parameters although melatonin implants appeared to reduce the number of unhealthy oocytes in the undernourished group (p < 0.05). During SA, in undernourished ewes exogenous melatonin tended to increase the number of healthy (L+MEL: 9.4 +/- 1.0, L-MEL: 7.6 +/- 1.4; p < 0.1), and significantly improved both cleaved oocytes (L+MEL: 7.0 +/- 0.7, L-MEL: 4.1 +/- 0.9; p < 0.05) and blastocyst rate (L+MEL: 37.2, L-MEL: 21.9%; p < 0.05). In conclusion, oocyte competence in ewes was affected by season, and melatonin implants appeared to improve developmental competence in the seasonal anoestrous period, particularly in experimentally undernourished ewes.

Timing of preovulatory LH surge and ovulation in superovulated sheep are affected by follicular status at start of the FSH treatment

The aims of this study were to evaluate the chronology of periovulatory events (oestrus behaviour, LH surge and ovulation) in 16 superovulated Manchega sheep and to determine whether follicular status at start of the FSH supply might affect their occurrence. Mean timing for onset of oestrus behaviour was detected at 28.1 +/- 0.7 h after sponge withdrawal; the preovulatory LH surge and ovulation started at 37.2 +/- 0.7 h and 65.4 +/- 0.7 h after progestagen withdrawal, respectively. The intervals between oestrus, LH surge and ovulation were affected by a high individual variability, which might be the cause for reported decreased efficiency in embryo production. Current results also addressed the role of follicular status at start of the superovulatory treatment on the preovulatory LH surge and the ovulation. The interval LH surge-ovulation was increased in ewes with a growing dominant follicle at starting the FSH treatment (32.3 +/- 0.9 vs 28.6 +/- 0.5 h, p < 0.05). The developmental stage of the largest follicle at starting the superovulatory treatment also affected occurrence of LH surge and ovulation; follicles in growing phase advanced the occurrence of the LH surge and ovulation when compared to decreasing follicles (33.0 +/- 1.0 vs 43.5 +/- 1.1 h, p < 0.05, for LH peak and 60.7 +/- 1.1 vs 72.8 +/- 1.2 h, p < 0.05, for ovulation). Thus, only ewes with growing follicles ovulated prior to 55 h after sponge withdrawal; conversely, no sheep with decreasing follicles ovulated earlier than 67 h, when an 85.7% of the ewes bearing growing follicles has ovulated at 63 h.

Day 0 Protocol: Superstimulatory treatment initiated in the absence of a large follicle improves ovarian response and embryo yield in goats

A new superstimulatory protocol (Day 0 Protocol) to initiate FSH treatment in the absence of a large follicle was compared to a traditional protocol in goats. The Day 0 Protocol (n=44) consisted of pre-treatment with progesterone and eCG to synchronize ovulation and the emergence of Wave 1, with FSH starting 84 h after the end of progesterone exposure (i.e., soon after ovulation). The traditional protocol (n=46) consisted of 11 d of progesterone exposure, with FSH treatment beginning 2 d before the end of progesterone exposure. Treatment with FSH was initiated in the absence of a large follicle in 37/44 and in 6/46 goats in the Day 0 Protocol and traditional protocol, respectively (P<0.01). There was more CL in the Day 0 Protocol than in the traditional protocol (breeding season: 9.6+/-0.6 and 6.3+/-0.8, P<0.05; non-breeding season: 14.3+/-1.5 and 10.7+/-1.5; P<0.05). More Grades 1 and 2 embryos were recovered in the Day 0 Protocol than in the traditional protocol (breeding season: 4.8+/-0.7 and 1.8+/-0.5, P<0.05; non-breeding season: 5.6+/-1.1 and 3.5+/-0.7, P=0.07). Similarly, the proportion of embryos that were Grades 1 and 2 was higher for the Day 0 Protocol than for the traditional protocol (breeding season: 81/114, 71%, versus 16/43, 37%, P<0.05; non-breeding season: 118/203, 58% versus 95/205, 46%, P<0.05). In summary, the Day 0 Protocol, was effective in initiating superstimulatory treatment in the absence of a large follicle, and compared to the traditional protocol, induced a higher ovulation rate and better embryo yield in goats.

Evidence of intraovarian follicular dominance effects during controlled ovarian stimulation in a sheep model

OBJECTIVE

To evaluate intraovarian dominance effects in a sheep model and to determine whether local factors, independent of FSH-mediated pathways, are capable of interfering with the final development of subordinate follicles.

DESIGN

Observational, model study.

SETTING

Public research unit.

ANIMAL(S)

Three hundred sixty-four adult Manchega ewes.

INTERVENTION(S)

Synchronization of estrous cycle with intravaginal progestogens and ovarian stimulation with FSH; ovarian ultrasonography, laparoscopies, and embryo recoveries.

MAIN OUTCOME MEASURE(S)

Determination of morphological characteristics and developmental competence of ovarian follicles.

RESULT(S)

The presence of a dominant follicle affects number and viability of embryos from the ipsilateral ovary in females that are treated with high FSH doses; this effect, modulated by season and phase of the estrous cycle, highlights the role of LH in follicular dominance.

CONCLUSION(S)

The current study confirms, in a sheep model, the existence of local effects from dominant follicles over neighboring follicles, by direct action and independently from systemic pathways through FSH modulation.

The effect of melatonin implants during the seasonal anestrus on embryo production after superovulation in aged high-prolificacy Rasa Aragonesa ewes

The aim of this study was to assess the effect of melatonin implants administered in March on the ovarian cyclicity, ovulatory response and embryo production after repeated superovulation of selected high-prolificacy Rasa Aragonesa aged ewes. During the seasonal anestrus of two consecutive years, 113 superovulatory treatments have been performed. Ewes were treated (M) or not (C) with melatonin implants in March (day 0). All of them received intravaginal progestogen sponges on day 24 (recovery 1) and 80 (recovery 2) after melatonin implants insertion in year 1, and on day 28 and 77 in year 2. The intravaginal sponges were removed after 14 days. Superovulatory treatments consisted of eight doses in decreasing concentrations (2 mL x 2 and 1 mL x 6) of oFSH (Ovagen) administered twice daily starting 72 h before sponge removal. Seven days after the onset of estrus, embryos were recovered by laparotomy. Melatonin increased cyclicity only in recovery 2 year 2 (83% versus 42%; P < 0.05) but not in the other experimental periods. Among the 78% (88) ewes that ovulated and produced functional corpora lutea, melatonin implants tended to improve embryo viability in recovery 2 by increasing the number of blastocysts per superovulatory treatment (2.4 +/- 0.6 versus 1.1 +/- 0.4; P = 0.09), the rate of viability (67 +/- 9% versus 43 +/- 9%; P < 0.05), and freezability (55 +/- 9% versus 33 +/- 8%; P < 0.05). More specifically, melatonin induced a significant reduction of the number and rate of non-viable (degenerate and retarded) embryos in recovery 2 (0.4+/-0.1 embryos versus 1.3 +/- 0.3 embryos and 4 +/- 1% versus 22 +/- 6%, respectively; P < 0.05). Our results demonstrate that melatonin implants in March can improve at medium term (3 months after implantation) the viability of embryos collected from selected high-prolificacy Rasa Aragonesa aged ewes after superovulation.

The Effect of the Manipulation of Follicle-Stimulating Hormone (FSH)-Peak Characteristics on Follicular Wave Dynamics in Sheep: Does an Ovarian-Independent Endogenous Rhythm in FSH Secretion Exist?1

We designed three experiments to investigate the relationship between FSH peaks and ovarian follicular waves and to examine whether an endogenous rhythm of FSH peaks exists in sheep. In experiment 1, anestrous ewes were treated with ovine FSH (oFSH) or vehicle (6 ewes per group) at the expected time of an endogenous FSH peak, to double the FSH-peak amplitude in treated ewes. In experiment 2, anestrous ewes were treated with either oFSH or vehicle (6 ewes per group) at the expected time of two consecutive interpeak nadirs, such that the treated ewes had 5 FSH peaks in the time frame of 3 FSH peaks in control ewes. In experiment 3, to measure FSH concentrations, daily blood samples were collected from 5 cyclic ewes for a control period during the estrous cycle and then for three 17-day periods after ovariectomy. Daily blood samples were collected from another group of 8 ovariectomized ewes that were treated with estradiol-releasing implants and intravaginal progestogen sponges. Doubling the FSH-peak amplitude did not alter the characteristics of the following follicular wave. Increasing the frequency of FSH peaks stimulated the emergence of additional follicular waves, but did not alter the rhythmic occurrence of FSH peaks and follicular wave emergence. Endogenous follicular waves in oFSH-treated ewes emerged and grew in the presence of the growing largest follicle of the induced follicular waves. Finally, based on the observation of serum FSH concentrations in ovariectomized ewes, it appears that there exists an endogenous rhythm for peaks in daily serum FSH concentrations, which is, at least in part, independent of regulation by ovarian follicular growth patterns.

The effects of previous ovarian status on ovulation rate and early embryo development in response to superovulatory FSH treatments in sheep

A total of 64 ewes was used to determine if the changes in superovulatory yields related to the ovarian status at the start of superovulatory treatment are due to differences in the population of gonadotrophin-responsive follicles, alterations in the processes of ovulation or transport of embryos from oviduct to uterus and/or developmental competence of the oocyte/embryo. Ovarian status at the start of a superovulatory FSH step-down treatment, administered coincidentally with a progestagen, was assessed by ultrasonography. On Day 4 after progestagen withdrawal, embryos were recovered from oviduct and their viability was determined by assessing development in vitro culture (IVC) until the hatched blastocyst stage. In all the ewes, the ovulation rate was related positively to the number of 2-3 mm follicles at first FSH injection (P<0.005). However, the total number of embryos and their viability were related to the more limited category of 3 mm follicles (P<0.05), whereas a higher degeneration rate was related to the number of 2mm follicles. The presence of a corpus luteum (CL) at the start of superovulatory treatment exerted a protective effect on embryonic viability, decreasing the degeneration of embryos. On the other hand, the presence of a dominant follicle at first FSH dose affected the mean size of the pool of follicles responding to the superovulation treatment, because ovulation arose from 3 to 5 mm follicles in absence of large follicles (P<0.05), but from 2 to 3 mm follicles when large follicles were present (P<0.005), indicating atresia in medium sized follicles in the presence of a large follicle.

Multiple factors affecting the efficiency of multiple ovulation and embryo transfer in sheep and goats

This review offers an overview of the basic characteristics of in vivo embryo technologies, their current status, the main findings and the advances gained in recent years, and the outstanding subjects for increasing their efficiency. The use of superovulation and embryo transfer procedures remains affected by a high variability in the ovulatory response to hormonal treatment and by a low and variable number of transferable embryos and offspring obtained. This variability has been classically identified with both extrinsic (source, purity of gonadotrophins and protocol of administration) and intrinsic factors (breed, age, nutrition and reproductive status), which are reviewed in this paper. However, emerging data indicate that the main causes of variability are related to endocrine and ovarian factors, and so the number of studies and procedures addressing a better understanding and control of these factors may be increased in the future. The accomplishment of this objective, the improvement of procedures for embryo conservation and for the selection and management of recipient females, will allow further development and application of this technology.

Effects of repetition, interval between treatments and season on the results from laparoscopic ovum pick-up in goats

The present study was conducted to evaluate the follicular response and oocyte yield following repeated gonadotrophin stimulation and laparoscopic aspiration in goats and to assess the effects of the time interval between procedures and season. A total of 98 adult goats were subjected to laparoscopic ovum pick-up (LOPU) five consecutive times in a transgenic production programme. Oestrus was synchronised by means of intravaginal sponges inserted for 10 days coupled with 125 μg cloprostenol 36 h before sponge removal and LOPU, and follicular development was stimulated with 80 mg follicle stimulating hormone and 300 IU equine chorionic gonadotrophin administered 36 h before LOPU. No difference was detected in the response for LOPUs 1, 2, 3 and 4. Although a small decrease in response was detected at LOPU 5 (P < 0.05), the numbers of follicles aspirated and oocytes recovered were not different from those at LOPU 1 and LOPUs 1 and 4, respectively. With respect to time interval between LOPU and season, all intervals and seasons produced acceptable responses, with no difference in follicles aspirated and oocytes recovered between intervals and seasons. These results indicate that LOPU may be repeated up to five times in goats at different intervals and in different seasons with little or no important change in overall response.