Superovulatory response following transvaginal follicle ablation in cattle

Benefits and Risks of Preventing Twin Pregnancies

Clinical problems associated with twin pregnancies have been well established, and twin births are now considered undesirable or even disastrous for the dairy cattle industry and the individual cow. The high incidence of early fetal loss, abortion during the mid-lactation period, dystocia, stillbirth, and placenta retention should be considered a preventable consequence of management, as these disorders greatly compromise the welfare and productive lifespan of a cow carrying or delivering twins. The use of sexed semen generates herd replacements and additional heifers, so a proposed strategy for twin pregnancy prevention is the transfer of a single in vitro-produced female beef cow embryo to cows not suitable for producing replacements. Another proposed strategy is drainage at insemination of co-dominant follicles to prevent twin pregnancies in cows with genetic merit. As a result, embryo survival should improve, economic losses associated with twin pregnancies will be prevented, beef output from the herd will be increased, and the health and welfare of the cow will certainly benefit. In this review, the clinical prospects of preventing or avoiding twin pregnancies using both procedures are discussed.

Identification of key bacterial populations affecting early embryonic development in cattle uterus

Superovulation is an important animal breeding biotechnology, while the quality of embryos obtained from superovulation is unstable in cattle. The relationship between the microorganisms in the cattle uterus and embryo qualities was determined to identify the key bacterial populations affecting early embryonic development. A total of 10 Xia Nan cows underwent superovulation, we collected cervical mucus and flush samples to investigated by 16S rDNA sequencing. Results showed that there were abundant microorganisms in cervical mucus, but no obvious relationship with the quality of embryos. The clustering results of flush samples were consistent with the grouping of embryo quality. Proteobacteria accounted for more than 95% of the total bacterial community in group A with the best embryo quality (qualified embryo ratio above 0.8), and as embryo quality decreased, the Proteobacteria proportion also decreased. In contrast to the proportion of Proteobacteria, the proportions of Firmicutes and Bacteroidetes significantly increased as embryo quality decreased. For group C with the worst embryo quality, the proportions of Firmicutes and Bacteroidetes increased to 4.7 times and 12.3 times of group A, respectively. These results showed that the quantities and proportions of Firmicutes and Bacteroidetes may be related to early embryonic development in cattle.

Factors affecting embryo production in superovulated Bos taurus cattle

Despite a long history of bovine superovulation research, significant commercial applications did not start until the early 1970s. For some 20 years thereafter, superovulation represented the primary tool for the production of cattle embryos. In the early 1990s, commercial invitro production (IVP) was initiated in cattle. Although ovum pick-up and IVP are now commercially practiced on a wide scale, superovulation and embryo recovery by flushing remain a widespread and very effective approach to the production of cattle embryos. This review covers both the history and the effects of multiple factors on superovulation in Bos taurus cattle. There are three general protocols for suitable pre-FSH programming of donors so that gonadotrophin-responsive follicles are available. Superovulation protocols vary widely based on the FSH source, the diluent used, the number and timing of FSH injections and the timing and utilisation of various prostaglandins, controlled internal progesterone releasing devices, gonadotrophin-releasing hormone, and other means of controlling follicular development and ovulation. The number of oocytes that can be stimulated to grow and ovulate within any given donor can be estimated by either ultrasound-guided sonography or by measuring concentrations of anti-Müllerian hormone in the blood. Animal-related factors that can influence the efficacy of superovulation include cattle breed, age, parity, genetics, lactational status and reproductive history. In addition, nutrition, stress, season, climate, weather and several semen factors are discussed.

A single administration of a long-acting recombinant ovine FSH (roFSH) for cattle superovulation

A recombinant long-acting ovine follicle stimulating hormone (roFSH) has been devised and its biological effectiveness following a single dose has been assessed in several experiments under field conditions, in pasture-based beef and dairy farming in New Zealand. Owing to the molecular structure of this long-acting roFSH, which includes additional N-glycosylation sites, a single dose combined with a simple CIDR-based superovulatory regime elicits successful ovarian stimulation with averages of 11.8 corpora lutea and of 6.1 good quality embryos collected in cattle. Solid performance of this novel FSH was demonstrated in several beef and dairy breeds which included yearling heifers and mixed age cows, with embryo production results in the same range as those observed nowadays with eight doses of commercial pituitary FSH (pFSH). Viable embryos produced from these collections, when implanted either fresh or frozen and thawed, gave pregnancy rates in recipients similar to those collected from cows and heifers superstimulated with pFSH. Repeated superovulatory treatment of the same cows was not associated with a decrease in ovarian response or embryo yield. The single administration of this long-acting roFSH when combined with a modified simple superovulatory regime has the advantage of reducing animal welfare concerns, lowering labour resource requirements and giving similar results to other commercially prepared pituitary FSH extracts.

Pursuit of a means of manipulating ovarian function in the cow: An adventure of serendipity, collaboration and friendship

A research career is not only built on ideas and publishable results; it is more often the product of determination, hard work, collegiality and collaboration. It is through our collaborators, family and friends that we really become better persons, and scientists. It is also a matter of being at the right place at the right time. My work in bovine reproduction has progressed from an interest in superovulation and embryo transfer before I became a veterinarian, to the development and application of this technology and fixed-time artificial insemination in beef and dairy herds. Everything that I have done has been possible because of the people that I have worked with over the years. This manuscript combines some of the very exciting things that I have learned about bovine reproduction over the last 30 years and personal stories behind the projects and ideas that we have pursued during that time.

Strategies to increment in vivo and in vitro embryo production and transfer in cattle

Knowledge of follicular wave dynamics obtained through the use of real-time ultrasonography and the development of the means by which follicular wave dynamics can be controlled have provided practical approaches for the in vivo and in vitro production and transfer of embryos in cattle. The elective control of follicular wave emergence and ovulation has had a great impact on the application of on-farm embryo transfer, especially when large groups of donors need to be superstimulated at the same time. Although estradiol and progestins have been used for many years, practitioners in countries where estradiol cannot be used have turned to alternative treatments, such as mechanical follicle ablation or the administration of GnRH for the synchronization of follicle wave emergence. In vitro embryo production also benefits from the synchronization of follicle wave emergence prior to Cumulus Oocyte Complexes (COCs) recovery. As Bos indicus cattle have high antral follicle population, large numbers of oocytes can be obtained by ovum pick-up (OPU) without superstimulation. However, synchronization of follicular wave emergence and superstimulation is necessary to obtain high numbers of COCs by OPU and blastocysts following in vitro fertilization in Bos taurus donors. Finally, embryos can now be transferred in commercial beef or dairy herds using efficacious synchronization and re-synchronization protocols that are easily implemented by farm personnel. These technologies can also be used to resolve reproductive problems such as the reduced fertility observed during summer heat stress and/or in repeat-breeder cows in commercial dairy herds.

Characterization and control of oocyte large-scale chromatin configuration in different cattle breeds

Differences in reproductive physiology between cattle breeds may help to explain distinct responses to assisted reproductive techniques and to define breed-specific protocols with improved efficiency. Germinal vesicle (GV) stage oocytes are characterized by increasing levels of chromatin compaction enclosed within the nucleus (graded from GV0 to GV3), associated with different developmental competence. The first objective of this study was to characterize chromatin configuration of GV stage oocytes recovered by OPU at random days of the estrous cycle from Nelore (Bos indicus) and Holstein (Bos taurus) cows. In Nelore 90% of the oocytes presented advanced stages of chromatin compaction associated with higher developmental competence (GV2 and GV3), while in Holstein, only 65% of the oocytes were at these stages. Then, aiming to obtain a more homogeneous population of oocytes in Holstein, we tested two synchronization protocols combining aspiration of all visible follicles at a random day (day 0), two IM injections of FSH 12 h apart on day 2, and OPU on day 4 (OPU/D4) or 5 (OPU/D5). The protocol OPU/D4 provided around 45% of the oocytes with low chromatin compaction (GV1), while the protocol OPU/D5 provided 70% of the oocytes at GV2 and 20% at GV3. Finally, we assessed the effects of a culture system known to prevent meiotic resumption on chromatin configuration of the GV2 enriched oocyte population obtained with the protocol OPU/D5. After 9 h of culture most oocytes transited from GV2 to GV3, with 90% of the oocytes at GV3 stage. This study demonstrates differences between Nelore and Holstein cows regarding patterns of chromatin configuration that may account for their different performance in IVM/IVF. In addition, it provides novel references for the design of protocols aiming to regulate oocyte quality before IVM for the optimization of IVF outcomes.

Synchronization of time of development of ovarian follicular waves in South American Camelids

South American camelids (SAC) are induced ovulating animals. In unmated females, ovarian follicle development occurs in waves of growth and regression, while mating when there is the presence of a mature follicle leads to ovulation. The capacity to respond to an ovulatory stimulus depends on the stage of the follicular wave development. Treatments to control ovarian follicular development have been performed to synchronize timing of wave emergence and development of the dominant follicle at a predictable time. Thus, synchronization of the time of follicular wave development allows for performing fixed time mating or artificial insemination, and superestimulatory treatments for multiple follicule development. Protocols are based on removal of the suppressive effect of the dominant follicle, that can be achieved by physical ablation or by inducing ovulation (with LH or GnRH) or atresia (with progesterone or progestagens alone or combined with estradiol) of this follicle. Differences between treatments should be taken into consideration when choosing a protocol for fixed time mating or artificial insemination, especially when applying the use these technologies for SAC production by commercial enterprises. Furthermore, the objective of applying synchronization protocols should be considered, because not all of these are effective in inhibiting follicular growth before initiation of a superestimulatory treatment for multiple follicle development.

Effects of endogenous progesterone during ovarian follicle superstimulation on embryo quality and quantity in beef cows

Despite modifications in techniques and protocols used for multiple ovulation embryo transfer in recent decades, transferrable quality embryos (TQE) has remained relatively unchanged. The objective of this study was to evaluate the effects of endogenous progesterone during beef cow superstimulation on embryo quality and quantity. Thirty non-pregnant beef cows were sorted into 1 of 5 replicates and randomly assigned to one of two groups: High Progesterone (HP) or Low Progesterone (LP). All cows, were pre-synchronized utilizing a 5-d CO-Synch + CIDR protocol. Nine days after estrus (d 0) with a corpus luteum present, all cows received ultrasound-guided dominant follicle ablation (DFA) and were administered a CIDR with LP cows also being administered PGF2α. All cows began a timed, 13-d, superovulation CIDR-based protocol and were artificially inseminated (AI) twice. Embryo were recovered and evaluated on each replicate 7 days after first AI. Blood samples were collected to evaluate progesterone (P4) and estradiol concentrations daily when cows were handled. Greater number of total embryos were recovered from the HP than the LP cows (19.26 vs. 10.74, P = 0.01). The HP cows also had greater number Stage 4 embryos along with more Quality Grade 3 and 4 embryos than the LP group (5.76 vs 2.20 P = 0.002; 1.87 vs 0.61, P = 0.01; 8.22 vs 2.89, P = 0.01, respectively). However, LP cows had a greater percentage overall of freezable embryos with a higher percentage of Grade 1 embryos (58.22 vs 37.32, P = 0.03) and a greater percentage of Stage 7 and 6 TQEs (18.47 vs 1.22, P = 0.01; 10.37 vs 3.19, P = 0.03). Serum P4 concentrations were greater on d 2-3 in the HP cows (P = 0.002). In addition, HP cows had greater concentrations of estradiol (P < 0.0001) on d 6. Comparatively, estradiol was greater in concentration in the LP cows (P ≤ 0.04) on d 2-4. In conclusion, removal of endogenous progesterone during superovulation may decrease the total number of embryos but increase the percentage of Grade 1 embryos and percentage of Stage 6 and 7 TQE in a single recovery.

Effect of the interval from follicle aspiration to initiation of lengthened FSH treatment on follicular superstimulatory and superovulatory responses and embryo production in lactating Simmental cows

The present study evaluated follicular superstimulatory (FSS) and superovulatory (SOV) responses and in vivo embryo production in lactating Simmental cows treated with FSH starting 1 or 2 days after follicle aspiration (FA). The performance of a lengthened superovulation program, named 6dFSH-P36-hCG60, is described. At random stages of the estrous cycle, cows (n = 52) were subjected to ultrasound-guided transvaginal aspiration of all follicles ≥ 5 mm. After FA, cows were randomly assigned to one of two groups in which FSH treatments started 1 or 2 days after FA (groups FA-1D and FA-2D, respectively). Cows were superstimulated with a total of 500 μg pFSH over 6 days on a decreasing dose schedule and were pre-treated with a single dose of 400 IU of eCG 24 h before the start of FSH treatments. Follicular superstimulatory (the mean numbers of follicles ≥ 8 mm on the day of hCG treatment) and SOV responses (the mean numbers of CL and cows with ≥ 3 CL at the time of collection) were similar in FA-1D and FA-2D groups. However, when compared to FA-1D group, the number of unfertilized ova tended to decrease (0.4 vs 1.7; P = 0.065) and percentage of fertilized ova tended to increase (95.8% vs 84.6%; P = 0.066) in FA-2D group. Moreover, the mean numbers and percentages of both transferable embryos (8.0 and 77.6% vs 6.4 and 57.7%) and freezable embryos (5.3 and 51.5% vs 3.5 and 31.1%) were numerically higher in FA-2D group than FA-1D group. The results of the study suggest that starting a lengthened superovulation programs in Simmental cows 2 days after FA has potential to increase percentage of fertilized ova and the number of transferable and freezable embryos, although new studies may be needed to confirm this findings.

Puncture and drainage of the subordinate follicles at timed artificial insemination prevents the risk of twin pregnancy in dairy cows

The objective of this study was to determine whether fluid drainage from the subordinate follicles by ovum pickup procedures prevents the risk of twin pregnancy without reducing the fertility of the cow. Lactating dairy cows with at least two follicles over 12 mm diameter located one on each ovary and selected from synchronized groups for fixed-time insemination were assigned to a Control (n = 49) or Drainage (n = 49) group. The largest follicle was considered as the dominant follicle. Draining of all subordinate follicles (≥10 mm) was performed in the Drainage group. All drained follicles developed as a corpus luteum 7 days later. In the Control cows, the presence of two corpora lutea (55.1%) was lower (p = .003) than those in the Drainage cows (87.8%), whereas the incidence of twin pregnancies was 50% and 0% for the Control and Drainage groups, respectively (p < .001). Draining did not affect the pregnancy rate. These results indicate that puncture and drainage of the subordinate follicles at insemination may eliminate the risk of twin pregnancies and reduce the risk of subsequent pregnancy loss by increasing the incidence of additional corpora lutea.

Characterization of blood flow and the effects of exogenous estradiol benzoate on residual follicles formed after ultrasound-guided transvaginal follicle aspiration in cattle

BACKGROUND

Removal of the follicular content by ultrasound-guided transvaginal follicle aspiration (TVFA) may fail to induce immediate atresia and loss of function, resulting in the occurrence of residual follicles (RF). The aims of this study were to characterize the blood flow in RF and to determine the effects of the treatment with estradiol benzoate on RF fate. Lactating, cyclic Holstein-Gir crossbred cows were used. In Experiment 1, follicular wave emergence (D0) was synchronized in cows (n = 10) and follicular growth was then monitored by transrectal ultrasonography from D0 to D8, followed by TVFA of the largest follicle present on the ovaries 24 h later. Color Doppler ultrasound imaging was used to examine blood flow on the follicular wall, which was recorded immediately before and every 12 h after TVFA, up to 72 h. In experiment 2, cows (n = 22) were randomly allocated to receive either 2 mL of saline i.m. (Control group, n = 11) or 2 mL estradiol benzoate i.m. (EB group, n = 11) immediately after TVFA. Ovaries were scanned every 12 h to confirm the presence and to measure the diameter of RF. The contents of the RF, if present, were collected 72 h after the first TVFA, using the same aspiration procedures. Follicular fluid from original follicles and RF were stored at -20 °C until hormonal assays.

RESULTS

In Experiment 1, there was no reduction (P > 0.05) of blood flow in the remaining follicle walls after TVFA and maximum blood flow values were observed at 49.5 ± 19.7 h post-TVFA. In Experiment 2, formation of RF after TVFA was proportionally similar between Controls (5/9) and EB (5/10) cows. Also, RF diameter did not differ between groups (P > 0.05). Nonetheless, the content of RF from cows in the EB group had lower (P = 0.0004) estradiol (E2) concentration and lower (P = 0.0005) E2:P4 ratio compared with Controls.

CONCLUSIONS

In conclusion, 1) the persistence of vascularization in the remaining follicle wall may contribute to the formation of RF after follicle aspiration, and 2) the treatment with estradiol benzoate does not prevent formation of RF, but does reduce their estradiol production.

Study of two strategies to induce follicular wave emergence for assisted reproductive treatments (ART)-a preliminary trial

PURPOSE

This study aimed to induce follicular wave emergence (FWE) using pharmacological (recombinant hCG administration) or mechanical (aspiration of dominant follicle) interventions in infertile women.

METHODS

Sixteen infertile women (≤35 years) with indications for in vitro fertilization due to tubal and/or male factor infertility were randomized into three groups: control (n = 6), pharmacological (n = 5) and mechanical (n = 5) groups. Women in both experimental groups underwent serial transvaginal sonograms (TVS) from menstrual cycle day 10 until identification of a dominant follicle ≥15 mm. Women in the pharmacological group received 250 μg of recombinant-hCG to induce ovulation, and resumed serial TVS 2 days later. In the mechanical group, dominant and subordinate follicles ≥10 mm were aspirated, and daily TVS was resumed on the following day. An increased pool of follicles ≥5 and ≤9 mm after interventions characterized FWE. Women in the control group underwent ovulation induction (OI) with 150 IU/day of recombinant follicle-stimulating hormone started on menstrual cycle day 3 (D3). OI was started on the day of FWE in the experimental groups. Endometrial asynchrony with development of the embryo was expected in the experimental groups. Therefore, all viable embryos were cryopreserved and transferred in an endometrial-stimulated cycle.

RESULTS

The number of follicles ≥5 and ≤9 mm increased after the interventions in both experimental groups (p < .001), indicating induction of FWE. OI outcomes were similar among the groups.

CONCLUSIONS

The pharmacological and mechanical interventions are efficient in inducing FWE; outcomes of OI synchronized with FWE should be further investigated.

Biomedical applications of ovarian transvaginal ultrasonography in cattle

Ovarian transvaginal ultrasonography (OTU) has been used world-wide for commercial ovum pick-up programs for in vitro embryo production in elite herds, providing an excellent model for the elucidation of factors controlling bovine oocyte developmental competence. Noninvasive sampling and treatment of ovarian structures is easily accomplished with bovine OTU techniques providing a promising system for in vivo delivery of transgenes directly into the ovary. The current review summarizes existing bovine OTU models and provides prospective applications of bovine OTU to undertake research in reproductive topics of biomedical relevance, with special emphasis on the development of in vivo gene transfer strategies.

In vivo embryo production in cows superovulated 1 or 2 days after ovum pick-up

The present study evaluated superovulatory responses and in vivo embryo production in cows treated with FSH starting 1 or 2 days after ovum pick-up (OPU). Thirty-three non-lactating Nelore cows were subjected to aspiration of all follicles ≥3mm for OPU. After OPU, cows were randomly divided into two groups in which the follicle superstimulatory treatments with FSH started 1 or 2 days after OPU (Groups D1 and D2, respectively). Data are presented as the least squares mean±s.e.m. The number of follicles ≥3mm before OPU was similar between groups (~34); however, cows in Group D2 had more follicles ≥3mm on the first day of FSH (15.2±2.3 vs 7.6±1.7; P=0.04) and a higher ratio of the number of follicles at first FSH/number of follicles before OPU (0.41±0.04 vs 0.24±0.02; P=0.01). In addition, Group D2 cows had a greater superovulatory response than did cows in Group D1 (18.9±2.8 vs 9.1±1.9 corpora lutea, respectively; P<0.03). However, there was no difference in the total number of recovered ova and embryos from cows in Groups D2 and D1 (5.1±1.4 vs 4.9±1.3, respectively; P>0.10). Nevertheless Group D2 cows had more freezable embryos than Group D1 cows (3.2±1.1 vs 1.3±0.5, respectively; P<0.05). Cows from Group D2 had a much higher proportion (P<0.001) of follicles ≥8mm compared with follicles ≥6mm and <8mm at the time of the last treatment with FSH. In conclusion, to obtain a greater production of viable embryos in superovulated cows after OPU, it is recommended to wait at least 2 days before starting FSH treatment.

Effect of vehicle and route of administration of letrozole on ovarian function in a bovine model

The objective of this study was to determine the effects of vehicle and route of administration of letrozole on ovarian function in sexually mature beef heifers. On Day 3 (Day 0 = ovulation), heifers were assigned randomly to four treatment groups and given 1 mg kg–1 letrozole intravenously (iv, n = 10) or intramuscularly (im, n = 10) or given a placebo iv (control iv, n = 5) or im (control im, n = 5). The interwave interval was longer in heifers treated with letrozole im than in im and iv controls (11.7 ± 0.30 vs 9.5 ± 0.50 and 10 ± 0.43, respectively; P < 0.05). Corpus luteum diameter profiles and plasma progesterone concentrations were greater (P < 0.03 and P < 0.05, respectively) in heifers treated with letrozole im compared with control im. Plasma oestradiol concentrations were lower in both letrozole-treated groups compared with controls (P ≤ 0.03). Plasma LH concentrations tended to be elevated at the time of wave emergence in heifers treated with letrozole im compared with other groups (group-by-day interaction, P = 0.06) and plasma FSH concentrations tended to be greater (P < 0.09) in heifers treated with letrozole by either route compared with a single control group. We conclude that intramuscular administration of letrozole in oil is a feasible route and vehicle for the development of a letrozole-based treatment protocol for herd synchronisation in cattle.

Aromatase inhibitor treatment with an intravaginal device and its effect on pre-ovulatory ovarian follicles in a bovine model

BACKGROUND

Letrozole, a non-steroidal aromatase inhibitor, prevents the body from producing its own estrogen. The objectives of the present study were to test the hypotheses that letrozole treatment, initiated prior to selection of the preovulatory dominant follicle, will induce the growth of more than one follicle to a pre-ovulatory size, and will delay ovulation.

METHODS

Post-pubertal beef heifers were given two luteolytic doses of PGF (12 h apart) and monitored by ultrasonography for ovulation. Five to eight days later, ovarian follicular wave emergence was synchronized by ultrasound-guided transvaginal follicular ablation (Day 0=wave emergence) and a luteolytic dose of PGF was given 60 and 72 h later. On Day 1, heifers were divided randomly into two groups (n=15/group) and an intravaginal device containing 1 g of letrozole or a blank device (control) was inserted. The intravaginal devices were removed on Day 7, or at the time of ovulation, whichever occurred first. Transrectal ultrasonography and blood sample collection were performed daily from the day of ablation to 12 days after subsequent ovulation.

RESULTS

The mean (+/-SEM) interval from device placement to ovulation was longer in letrozole-treated animals compared to controls (6.1+/-0.25 vs 5.1+/-0.26 days, respectively; P<0.01). Single dominant follicles were present in both groups. The day-to-day diameter profiles of the dominant follicles of the ovulatory wave were larger (P<0.05) and the maximum diameters greater in letrozole-treated heifers (14.6+/-0.51 vs 12.4+/-0.53 mm, respectively; P<0.01). The diameter profile of the corpus luteum (CL) that formed after treatment did not differ between groups; however, plasma progesterone concentrations were higher (P<0.01) in heifers treated with letrozole. Estradiol concentrations were reduced following letrozole treatment (P<0.05), although a preovulatory rise of estradiol occurred in both groups.

CONCLUSIONS

Administration of letrozole with an intravaginal device during growth of the ovulatory follicle delayed ovulation by 24 h and resulted in the formation of a CL that secreted higher levels of progesterone. A sustained-release intravaginal device may be useful for the development of an aromatase inhibitor-based protocol to control ovulation for herd synchronization and to enhance fertility by increasing circulating progesterone concentrations during the first 7 days post-ovulation in cattle.

The evolution of improved and simplified superovulation protocols in cattle

Superovulation protocols have improved greatly since the early days of bovine embryo transfer when purified gonadotrophins were not available, follicular wave dynamics were unknown physiological phenomena and prostaglandins were not available. Although superstimulatory protocols in cattle are normally initiated mid-cycle, elective control of follicular wave emergence and ovulation have had a great impact on the application of on-farm embryo transfer. However, the most common treatment for the synchronisation of follicular wave emergence involves the use of oestradiol, which cannot be used in many parts of the world. Therefore, the need for alternative treatments has driven recent research. An approach that has shown promise is to initiate follicle-stimulating hormone (FSH) treatments at the time of the emergence of the new follicular wave following ovulation induced by gonadotrophin-releasing hormone. Alternatively, it has been shown that it may be possible to ignore follicular wave status and, by extending the treatment protocol, induce subordinate follicles to superovulate. Finally, the short half-life of pituitary FSH necessitates twice-daily treatments, which are time-consuming, stressful and subject to error. Recent treatment protocols have permitted superstimulation with a single FSH treatment or two treatments 48 h apart, reducing the need for animal handling during gonadotrophin treatments.

A bovine model for examining the effects of an aromatase inhibitor on ovarian function in women

OBJECTIVE

To test the hypothesis that treatment with an aromatase inhibitor (letrozole) will terminate dominant ovarian follicle growth and result in the emergence of a new follicular wave, regardless of the stage of follicular development at the time of treatment.

DESIGN

Prospective study.

SETTING

Academic research center.

ANIMAL(S)

Postpubertal beef heifers.

INTERVENTION(S)

Randomized trial involving treatment with letrozole on days 1-3, 3-5, 5-7 (day 0 = pretreatment ovulation) or no treatment.

MAIN OUTCOME MEASURE(S)

Follicular development, corpus luteum (CL) development, hormone profiles, and plasma aromatase inhibitor concentration.

RESULT(S)

Multiple doses of letrozole lengthened the period of follicular dominance, delayed emergence of the next follicular wave, and resulted in a larger CL regardless of the stage of the follicular wave in which treatments were initiated. No effects on circulating FSH concentrations were detected, but the stimulatory effects on the dominant follicle and CL were associated with increased plasma concentrations of LH in letrozole-treated animals. Plasma P concentrations were numerically higher throughout the luteal phase in letrozole-treated versus control heifers, but differences were not significant.

CONCLUSION(S)

The results provide rationale for the hypothesis that the mechanism of action responsible for the stimulatory effect of aromatase inhibitors on ovarian function involves an elevation in circulating concentrations of LH rather than FSH.

Induction of ovarian follicular wave emergence in wapiti (Cervus elaphus)

Two experiments were done to test the effects of treatments designed to electively induce ovarian follicular wave emergence in wapiti for the purpose of group synchronization. In Experiment 1, hinds were assigned randomly to three groups and given saline im (controls; n=5), 5mg of estadiol-17beta im (n=4), or 5mg estradiol-17beta plus 100mg progesterone im (n=5). In Experiment 2, hinds were assigned randomly to two groups and given no treatment (controls; n=6), or transvaginal ultrasound-guided follicle ablation (n=7). In both experiments, ovarian follicular dynamics were monitored by daily transrectal ultrasonography from Day 0 (day of treatment) to Day 9. In Experiment 1, blood samples were collected at each examination for measurement of serum concentrations of progesterone and FSH. Both experiments were conducted during the late anestrous period (July and August). The mean (+/-S.E.M.) day of wave emergence did not differ between the control and estradiol alone groups, but tended to be later in the estradiol plus progesterone group Day 4.0+/-0.7, Day 3.5+/-0.3, and Day 5.2+/-0.2, respectively; P=0.06). The interval from treatment to wave emergence was less variable in the estradiol plus progesterone group (P<0.05) and tended to be less variable in the estradiol-alone group (P=0.07) than in the control group. The day of wave emergence was more variable (P<0.05) and tended to be later (P=0.10) in the control group compared to the ablation group (Day 2.5+/-0.8 versus Day 1.4+/-0.2). All three treatments were effective in synchronizing ovarian follicular wave emergence among a group of wapiti hinds. Follicle ablation may be an alternative method for synchronization of follicular waves in estrus synchronization and superstimulatory protocols.

Effects of plasma progesterone concentrations on LH release and ovulation in beef cattle given GnRH

The effects of plasma progesterone concentrations on LH release and ovulation in beef cattle given 100 microg of GnRH im were determined in three experiments. In Experiment 1, heifers were given GnRH 3, 6 or 9 days after ovulation; 8/9, 5/9 and 2/9 ovulated (P<0.02). Mean plasma concentrations of progesterone were lowest (P<0.01) and of LH were highest (P<0.03) in heifers treated 3 days after ovulation. In Experiment 2, heifers received no treatment (Control) or one or two previously used CIDR inserts (Low-P4 and High-P4 groups, respectively) on Day 4 (estrus=Day 0). On Day 5, the Low-P4 group received prostaglandin F(2alpha) (PGF) twice, 12 h apart and on Day 6, all heifers received GnRH. Compared to heifers in the Control and Low-P4 groups, heifers in the High-P4 group had higher (P<0.01) plasma progesterone concentrations on Day 6 (3.0+/-0.3, 3.0+/-0.3 and 5.7+/-0.4 ng/ml, respectively; mean+/-S.E.M.) and a lower (P<0.01) incidence of GnRH-induced ovulation (10/10, 9/10 and 3/10). In Experiment 3, 4-6 days after ovulation, 20 beef heifers and 20 suckled beef cows were given a once-used CIDR, the two largest follicles were ablated, and the cattle were allocated to receive either PGF (repeated 12h later) or no additional treatment (Low-P4 and High-P4, respectively). All cattle received GnRH 6-8 days after follicular ablation. There was no difference between heifers and cows for ovulatory response (77.7 and 78.9%, P<0.9) or the GnRH-induced LH surge (P<0.3). However, the Low-P4 group had a higher (P<0.01) ovulatory response (94.7% versus 61.1%) and a greater LH surge of longer duration (P<0.001). In conclusion, although high plasma progesterone concentrations reduced both GnRH-induced increases in plasma LH concentrations and ovulatory responses in beef cattle, the hypothesis that heifers were more sensitive than cows to the suppressive effects of progesterone was not supported.

Serum biochemical parameters and embryo production during superovulatory treatment in dairy cattle

The objective of this study was to determine the relationship between the number of transferable embryos (TE) and various blood chemistry parameters as a reflection of the metabolic state of cows after superovulatory treatment. Forty-nine Holstein cows were subjected to superovulatory treatment for commercial embryo production. At the time of embryo harvest, individual blood samples were taken from cows for biochemical analysis. All embryos including dead ones as well as non-fertilized oocytes were counted in uterine lavage. Feed samples collected daily for a period of two weeks before embryo harvest, were analyzed for mycotoxins: vomitoxin, zearalenone and T-2 toxin. On average, cows produced 9.45+/-5.60 embryos and oocytes of which 5.27+/-4.20 were TE, 0.37+/-0.80 were dead embryos and 3.82+/-3.78 were non-fertilized oocytes. Higher concentrations of Mg and K were associated with a higher production of TE (p=0.005 and p=0.043, respectively) and higher activity of creatinine kinase was associated with a lower production of TE (p=0.011).

In vitro oocyte maturation, fertilization and culture after ovum pick-up in an endangered gazelle (Gazella dama mhorr)

The recovery of immature oocytes followed by in vitro maturation, fertilization and culture (IVMFC) allows the rescue of biological material of great genetic value for the establishment of genetic resource banks of endangered species. Studies exist on sperm cryopreservation of endangered Mohor gazelle (Gazella dama mhorr), but no work has been carried out yet on oocyte collection, fertilization and culture in this or related species. The purpose of this study was to develop a protocol for ovarian stimulation for the recovery of oocytes and subsequent IVMFC in the Mohor gazelle using frozen-thawed spermatozoa. Ovum pick-up was performed after ovarian stimulation with a total dose of 5.28 mg of ovine FSH. A total of 35 oocytes were recovered from 56 punctured follicles (62%) (N=6 females). Out of 29 cumulus-oocyte complexes matured in vitro, 3% were found at germinal vesicle stage, 7% at metaphase I, 21% were degenerated, and 69% advanced to metaphase II. Fertilization and cleavage rates of matured oocytes were 40 and 30%, respectively. Embryos cleaved in vitro up to the 6-8 cell stage but none progressed to the blastocyst stage, suggesting the existence of a developmental block and the need to improve culture conditions. Although more studies are needed to improve hormonal stimulation and oocyte harvesting, as well as IVMFC conditions, this study demonstrates for the first time the feasibility of in vitro fertilization with frozen-thawed semen of in vitro matured oocytes collected by ovum pick-up from FSH-stimulated endangered gazelles.

Alternative approaches to setting up donor cows for superstimulation

Protocols that controlled follicular wave emergence and ovulation have had a great impact on the application of on-farm embryo transfer, as they permitted the initiation of superstimulatory treatments at a self-appointed time. However, the most commonly used approach for synchronization of follicular wave emergence involved estradiol, which cannot be used in many countries. Therefore, alternative treatments are required. Mechanical removal of the dominant follicle by ultrasound-guided follicle aspiration was effective, but required the use of specialized equipment and trained technical staff, which made it difficult to utilize in the field. Exogenous GnRH or pLH have also been used to induce ovulation of a dominant follicle, synchronizing follicular wave emergence, but their efficacy was dependent on the stage of the dominant follicle at treatment; thus, the emergence of the ensuing follicular wave may be too variable for superstimulation. An alternative approach could be initiating treatments at the time of emergence of the first follicular wave, but the need to synchronize ovulation may be a disadvantage in groups of donors at random stages of the estrous cycle. The final alternative may be to use FSH or eCG to initiate a new wave, without regard to the presence of a dominant follicle, followed by superstimulatory treatment at a predetermined time. All alternatives need to be thoroughly investigated in order to confirm their utility in the superstimulation of donor cows, regardless of the stage of the estrous cycle and without compromising ova/embryo production.

Effect of estradiol benzoate or GnRH treatment prior to superstimulation in CIDR-treated, Korean native cows (Bos taurus)

The objective of this study was to evaluate the effectiveness of superovulatory protocols by synchronizing the emergence of the follicular wave using estradiol benzoate (EB) or GnRH in CIDR-treated, Korean cows. Sixty-six cows were used in the study and these were divided into three groups. The standard group comprised cows that were between days 8 and 12 of their estrous cycle (n=22). The remaining 44 cows, at all other stages of the estrous cycle, received CIDR and were assigned to two treatment groups that received either 2mg EB (EB-CIDR group, n=22) or 100 microg GnRH (GnRH-CIDR group, n=22) 1 day after CIDR insertion. Gonadotropin treatment began between the 8th and 12th days of the estrous cycle in the standard group, 5 days after EB injection in the EB-CIDR group, and 3 days after GnRH injection in the GnRH-CIDR group. All cows were superovulated with porcine FSH (pFSH) twice daily, with the dose (total 28 mg) decreasing gradually over 4 days. On the 5th and 6th injections of pFSH, 25 and 15 mg doses of PGF(2alpha) were administered. CIDR was withdrawn at the 7th pFSH injection and the cows received 200 microg GnRH at 24h after CIDR withdrawal. Cows were artificially inseminated twice at 36 and 48 h post-CIDR withdrawal and embryos were recovered 7 days after the 1st insemination. The numbers of preovulatory follicles (22.9-28.2), ovulated preovulatory follicles (17.6-21.7) and CL (15.9-17.9) detected by ultrasonography did not differ among groups (P>0.05). Similarly, the numbers of total ova (6.7-10.0), transferable embryos (4.0-6.0), degenerate embryos (1.1-1.8) and unfertilized ova (1.3-4.3) did not differ among groups (P>0.05). Progesterone and estradiol concentrations during superovulation treatments and at embryo recovery were also the same in all groups (P>0.05). We conclude that in CIDR-treated Korean native cows, superovulatory treatments that follow administration of either EB or GnRH (at any stage of the estrous cycle) result in both a superovulatory response and embryo yield comparable to conventional superovulation protocols.

Improved superovulatory response in beef cattle following ovarian follicular ablation using a simplified transvaginal device

The influence of the timing for the ablation of dominant follicle(s) prior to superovulatory treatment, and its effect on ovarian follicular growth and embryo yield, still remain elusive in cattle. The present study was designed to evaluate the effects of: (1) the day of the estrous cycle, at mid-diestrus, for the onset of superstimulation of follicular development, (2) the presence or absence of large ovarian follicles (ovary status) and (3) the time of follicular ablation, in hours, prior to the superovulatory treatment, on the superovulatory response in cattle. From a total of 244 superovulatory treatments and embryo collections in nulliparous and multiparous females, 76 were conducted after follicular ablation using a simplified transvaginal puncture cannula. Results from the present study indicated that the presence of large palpable follicle(s) at the onset of superstimulation of follicular development markedly reduced the superovulatory response. In addition, follicular ablation at 0 h or at 24 h prior to the onset of the superstimulation treatment significantly increased the number of total viable embryos. However, superovulatory responses were not affected by the day of the estrous cycle for the onset of follicular superstimulation and by the animal category (heifers or cows). In conclusion, the ablation of palpable follicle(s) 24 h or immediately prior to the onset of gonadotropin treatment, from days 8 to 12 of the estrous cycle (day 0, behavioral estrus), increased the total number of transferable embryos per flushing in cattle.

Follicle Ablation Improves the Ovarian Response and the Number of Collected Embryos in Superovulated Cows During the Early Stages of Lactation

A field study was designed to compare ovarian response and embryo yield in cows during early lactation when gonadotropin administration followed one of four treatments. In group 1A (n = 19) and 1B (n = 9), the estrouses were synchronized by two prostaglandin F2alpha (PG) injections given 11 days apart, and starting from day 9 of the synchronized cycle superovulation was conducted with eight decreasing dose of FSH. In group 1B, ablation of all follicles >3 mm was carried out on day 8. In group 2A and 2B (each n = 9), a progesterone plus oestradiol intravaginal device (PRID) was inserted for 11 days and gonadotropin administration started on day 9, while cows from group 2B had a follicle ablation on day 8. In all groups, two PG injections were given along with the sixth and the seventh dose of FSH, and the cows were twice inseminated 12 and 24 h after estrus detection. Embryos were collected on day 7. In cumulative results from aspirated and non-aspirated cows, follicular ablation significantly improved: the ovarian response (10 +/- 1.23 vs 6.69 +/- 0.60 corpora lutea per donor), the mean collected embryos (6.57 +/- 0.94 vs 2.46 +/- 0.53) and the mean transferable embryos (4.43 +/- 0.89 vs 2.18 +/- 0.47). Group 1B and 2B cows had better ovarian response than 1A (6.44 +/- 0.81, 12.25 +/- 4.11 and 9.44 +/- 0.93, for groups 1A, 1B and 2B, respectively, p < 0.05). Similarly, from groups 1B and 2B more (p < 0.05) embryos were collected in comparison with their respective group, while the mean transferable embryos from group 2B (5.22 +/- 1.13) was greater (p < 0.05) than that of group 1A (1.67 +/- 0.35), and tented to be greater than those of groups 2A (3.44 +/- 1.19, p = 0.062) and 1B (3.00 +/- 1.78, p = 0.066). The highest (p < 0.05) transferable embryo collection rate was recorded in group 2B (55.29%), followed by that of group 1B (41.33%). In summary, early in lactation, an acceptable number of transferable embryos can be collected from high producing dairy cows, when follicle ablation prior to superovulation is combined with progesterone and oestradiol administration.

The timing of ovulation and insemination schedules in superstimulated cattle

The development of treatments that control follicular wave dynamics during the bovine estrous cycle has resulted in interesting possibilities for the precise control of follicular wave emergence and the time of ovulation. For superstimulation, follicular wave emergence can be controlled by ultrasound-guided follicle ablation with FSH treatments initiated 1 or 2 d later, or injection of estradiol combined with progesterone at the time of insertion of a progestogen releasing device and FSH treatments beginning 4 d later. These are the most widely used protocols for superstimulation of donor cows because they offer the convenience of being able to initiate treatments quickly and at a self-appointed time, without reducing the number of transferable embryos. However, these protocols still require precise estrus detection of donors following superstimulation in order to conduct AI at the most appropriate time. Recent studies have been designed to develop superstimulation protocols that involve fixed-time AI of donors, without regard to estrus detection. Results presented herein indicate that delaying the removal of a progestogen releasing device, combined with the administration of GnRH or porcine LH (pLH) 12 or 24 h later results in predictable, synchronous ovulations, permitting fixed-time AI without reducing the numbers or quality of embryos. These protocols facilitate the application of on-farm embryo transfer programs because they are practical, easy to administer by farm personnel, and more importantly, they eliminate the need for detecting estrus.

The effect of pretreatment with different doses of GnRH to synchronize follicular wave on superstimulation of follicular growth in dairy cattle

The objective of this study was to evaluate the efficiency of gonadotropin releasing hormone (GnRH) and GnRH doses in synchronizing follicular wave emergence as a pretreatment for superovulation in cattle. Fourteen Holstein-Friesian cows 6 days from estrus were randomly assigned to receive 100 microg (n=4), 50 microg (n=5), or 25 microg (n=5) of GnRH. Superovulation was induced with injections of porcine FSH (pFSH) twice daily, decreasing the dose (total 42 AU) over 5 days beginning 2.5 days after receiving GnRH. On the 7th and 8th injections of pFSH, 750 microg of PGF(2alpha) was also given. With the exception of one cow that was given 50 microg of GnRH, ovulation was induced in all cows from the three groups and the new follicular wave emergence was observed. The total number of follicles for the 25 microg GnRH group was less than that observed for the 100 microg GnRH group (P<0.05), although there were no differences between the 100 microg, 50 microg and 25 microg GnRH groups with respect to the number of preovulatory follicles (>or=10 mm) and CL. The numbers of normal embryos were greater for the 25 microg GnRH group than the 100 or 50 microg GnRH groups (P<0.01); however, the numbers of ova/embryos did not differ significantly between the three groups. These results suggest that 25 microg of GnRH was sufficient to induce ovulation and follicular wave emergence. On day 6 of the estrous cycle, a reduction of the dose of GnRH to synchronize follicular wave emergence as a pretreatment for superstimulation promotes transferable embryos.

Effect of estradiol valerate on ovarian follicle dynamics and superovulatory response in progestin-treated cattle

Three experiments evaluated the effects of estradiol valerate (EV) on ovarian follicular and CL dynamics, intervals to estrus and ovulation, and superovulatory response in cattle. Experiment 1 compared the efficacy of two norgestomet ear implants (Crestar and Syncro-Mate B; SMB) for 9 d (with PGF at implant removal), combined with either 5 mg estradiol-17beta and 100 mg progesterone (EP) or 5 mg EV and 3mg norgestomet (EN) im at the time of implant insertion on CL diameter and follicular wave dynamics. Ovaries were monitored by ultrasonography. There was no effect of norgestomet implant. Diameter of the CL decreased following EN treatment (P < 0.01). Mean (+/- S.D.) day of follicular wave emergence (FWE) was earlier (P < 0.0001) and less variable (P < 0.0001) in EP- (3.6 +/- 0.5 d) than in EN- (5.7 +/- 1.5 d) treated heifers. Intervals from implant removal to estrus (P < 0.001) and ovulation (P < 0.01) were shorter in EN- (45.7 +/- 11.7 and 74.3 +/- 12.6 h, respectively) than in EP- (56.4 +/- 14.1 and 83.3 +/- 17.0 h, respectively) treated heifers. Experiment 2 compared the efficacy of EP versus EN in synchronizing FWE for superovulation in SMB-implanted cows. At random stages of the estrous cycle, Holstein cows (n = 78) received two SMB implants (Day 0) and were randomly assigned to receive EN on Day 0 or EP on Day 1. Folltropin-V treatments were initiated on the evening of Day 5, with PGF in the morning and evening of Day 8, when SMB were removed. Cows were inseminated after the onset of estrus and embryos were recovered 7 d later. Non-lactating cows had more CL (16.7 +/- 11.3 versus 8.3 +/- 4.9) and total ova/embryos (14.7 +/- 9.5 versus 7.9 +/- 4.6) than lactating cows (P < 0.05). EP-treated cows tended (P = 0.09) to yield more transferable embryos (5.6 +/- 5.2) than EN-treated cows (4.0 +/- 3.7). Experiment 3 compared the effect of dose of EV on ovarian follicle and CL growth profiles and synchrony of estrus and ovulation in CIDR-treated beef cows (n = 43). At random stages of the estrous cycle (Day 0), cows received a CIDR and no further treatment (Control), or an injection of 1, 2, or 5 mg im of EV. On Day 7, CIDR were removed and cows received PGF. Follicular wave emergence occurred within 7 d in 7/10 Control cows and 31/32 EV-treated cows (P < 0.05). In responding cows, interval from treatment to FWE was longer (P < 0.05) in those treated with 5 mg EV (4.8 +/- 1.2 d) than in those treated with 1 mg (3.2 +/- 0.9 d) or 2 mg (3.4 +/- 0.8 d) EV, while Control cows were intermediate (3.8 +/- 2.0 d). Diameter of the dominant follicle was smaller (P < 0.05) at CIDR removal and tended (P = 0.08) to be smaller just prior to ovulation in the 5 mg EV group (8.5 +/- 2.2 and 13.2 +/- 0.6 mm, respectively) than in the Control (11.8 +/- 4.6 and 15.5 +/- 2.9 mm, respectively) or 1mg EV (11.7 +/- 2.5 and 15.1 +/- 2.2 mm, respectively) groups, with the 2mg EV group (10.7 +/- 1.5 and 14.3 +/- 1.7 mm, respectively) intermediate. Diameter of the dominant follicle at CIDR removal was less variable (P < 0.01) in the 2 and 5mg EV groups than in the Control group, and intermediate in the 1mg EV group. In summary, treatment with 5mg EV resulted in a longer and more variable interval to follicular wave emergence than treatment with 5mg estradiol-17beta, which affected preovulatory dominant follicle size following progestin removal, and may have also affected superstimulatory response in Holstein cows. Additionally, 5 mg EV appeared to induce luteolysis in heifers, reducing the interval to ovulation following norgestomet removal. Conversely, intervals to, and synchrony of, follicular wave emergence, estrus and ovulation following treatment with 1 or 2 mg EV suggested that reduced doses of EV may be more useful for the synchronization of follicular wave emergence in progestogen-treated cattle.

A simple ultrasound test to predict the superstimulatory response in cattle

We tested the hypotheses that: (1) the superstimulatory response is related to the intrinsic number of follicles recruited into a follicular wave; and (2) the number of follicles recruited into a wave is correlated to the number of follicles recruited into the successive wave. A positive correlation will form the basis of a test for predicting the superstimulatory response. Cows (n = 141) were treated with estradiol and progesterone to synchronize follicular wave emergence (first synchronization) and ranked according to the number of follicles > or =2mm at wave emergence to select the upper and lower 10% of the herd. Follicular wave emergence was synchronized again in the high-end (n = 16) and low-end (n = 20) groups (second synchronization), and cows were treated with FSH twice daily for 3 days. High-end cows had a greater number of follicles (P < 0.001) than low-end cows at the time of wave emergence after both the first and second synchronizations in the 2-3 and 4-6mm categories. The numbers of 2-3 and 4-6mm follicles at wave emergence after the first and second synchronizations were positively correlated (P < 0.001; r = 0.77 and 0.71, respectively). Endogenous FSH peak at the time of wave emergence was higher in the low-end group than in the high-end group. Superstimulatory treatment resulted in more than double the number of follicles (P < 0.003) in the 5-7mm and > or =8mm categories in the high-end group than in the low-end group (16.8 +/- 2.2 versus 8.1 +/- 0.9 and 22.7 +/- 4.1 versus 9.7 +/- 1.6, respectively). The number of follicles > or =5 and > or =8mm at the end of superstimulation was positively correlated (P < 0.001) with the total number of follicles > or =2mm at the time of wave emergence after both the first (r = 0.64 and 0.54, respectively) and second ( r = 0.65 and 0.5, respectively) synchronizations. Based on the results of this study, the superstimulatory response can be predicted by the number of follicles > or =2mm at wave emergence. For practical purposes, practitioners can expect the number of follicles > or =5mm after ovarian superstimulation to be approximately 71% of the number of follicles > or =2mm at the time of wave emergence. Results validated the proposed simple ultrasound-based test for predicting the superstimulatory response of individual cows.

FSH different regimes affect the developmental capacity and cryotolerance of embryos derived from oocytes collected by ovum pick-up in donor sheep

The objective of the present study was to compare the developmental capacity of sheep oocytes obtained by OPU after two different ovarian stimulations, and cryotolerance to vitrification procedures of in vitro derived embryos after in vitro maturation, fertilisation and culture of these oocytes. Sheep were divided into three groups: (A) no treatment (control); (B) constant doses of FSH (FSH-c); (C) decreasing doses of FSH (FSH-d). Ovine groups FSH-c and FSH-d were synchronised by the insertion of intravaginal sponges left in situ for 7 days; FSH (total dose: 96IU) was administered in four doses given every 12h starting on Day 5. Twelve hours after the last FSH administration oocytes were collected by OPU technique. The control group showed a significantly lower number ( P<0.05 ) of follicles (166) than FSH-c (294) and FSH-d (317) groups, while the number of follicles >5mm was significantly higher ( P<0.01 ) in FSH-d group, showing that this protocol stimulates the growth of a different follicle population compared to FSH-c group. The control group showed a higher number of <2mm follicles ( P<0.01 ). We did not find any difference in oocyte quality between the three groups and therefore the percentage of discarded oocytes was similar. No significant differences were found between control, FSH-c and FSH-d groups in terms of maturation (90.9, 85.7 and 87.7%, respectively) and fertilisation rates (75.2, 80.9 and 83.7%, respectively) while a significantly higher ( P<0.01 ) blastocyst rate was observed in the FSH-c group than in the FSH-d and control groups (20.4% versus 11.8 and 13.7%, respectively). After vitrification, warming and 72 h in vitro culture, the hatching rate was significantly higher ( P<0.01 ) in the control (87.5%) and FSH-c (90.5%) groups than in the FSH-d group (66.7%). Control and FSH-c groups showed a significantly higher ( P<0.001 ) number of total cells than FSH-d group ( 217.6+/-26.5 and 203.0+/-33.2 versus 147.5+/-20.2 ), while no differences were observed in ICM cell rates in the control ( 35.6+/-3.8 ), FSH-c ( 37.1+/-4.6 ) and FSH-d ( 36.6+/-6.7 ) groups. These results indicate that donor sheep stimulated with FSH-c produced better quality oocytes and blastocysts showing better cryotolerance than ewes given the decreasing doses treatment.

Ovarian follicular wave synchronization and pregnancy rate after fixed-time natural mating in llamas

The study was designed to compare the efficacy of treatments intended to induce follicular wave synchronization among llamas (Experiment 1), and to determine the effect of these treatments on pregnancy rates after fixed-time natural mating (Experiment 2). In Experiment 1, llamas were treated with: (1) saline (control, n=20); (2) estradiol and progesterone (E/P, n=20); (3) LH (LH, n=20); or (4) transvaginal ultrasound-guided follicle ablation (FA, n=20). The ovarian response was monitored daily by transrectal ultrasonography. The intervals from treatment to follicular wave emergence and to the day on which the new dominant follicle reached >/=7 mm, respectively, did not differ between the LH (2.1+/-0.3 days and 5.2+/-0.5 days, respectively) and FA groups (2.3+/-0.3 days and 5.0+/-0.5 days), but both were shorter (P<0.05) and less variable (P<0.01) than in the control group (5.5+/-1.0 days and 8.4+/-2.0 days), while the E/P group (4.5+/-0.8 days and 7.7+/-0.5 days) was intermediate. In Experiment 2, llamas at unknown stages of follicular development were assigned randomly to control, E/P, and LH groups (n=30 per group). A single, fixed-time natural mating was permitted 10-12 days after treatment. Ovulation rates did not differ among groups (control, 93%; E/P, 90%; LH, 90%; P=0.99), but the pregnancy rate was higher (P<0.05) for synchronized llamas (LH and E/P groups combined, 41/54) than for non-synchronized llamas (control group, 15/28). In conclusion, LH and FA treatments were most effective for inducing follicular wave synchronization, while E/P treatment was intermediate. Synchronization treatments did not influence ovulation rate subsequent to fixed-time natural mating, but a higher pregnancy rate in synchronized than non-synchronized llamas warrants critical evaluation of the effects of follicular status on the developmental competence of the contained oocyte.

Effects of epidural injections and transvaginal aspiration of ovarian follicles in heifers used repeatedly for ultrasound-guided retrieval of ova and embryo production

Postmortem examinations of 13 Simmental heifers that had received between 16 and 28 injections to induce caudal epidural anaesthesia, the last not less than seven months before they were slaughtered, showed that none of them had any evidence of infection or inflammation at the injection site or in adjacent bone and soft tissues. Seven of them had minor damage to intercoccygeal discs, consisting of discospondylosis with neovascularisation and chondroid metaplasia, consistent with injuries caused by needles. The severity of the damage was not related to the number of epidural injections received, suggesting that the damage was probably caused by a discrete suboptimal injection procedure. In a second study, the ovaries from 22 Simmental heifers that had undergone between 13 and 16 transvaginal follicular aspirations were examined postmortem. Approximately one-third of them had a natural texture with little or no evidence of scar tissue, and less than one in five had extensive scarring and a toughened texture. There was no evidence of compromised ovarian function, as determined by the number and normality of corpora lutea and large follicles, in any of the animals.

Manipulation of follicular development to produce developmentally competent bovine oocytes

Superstimulation in donor cows increases the number of cumulus-oocyte complexes (COC), but when compared to in vivo maturation, in vitro maturation results in only half as many blastocysts after prolonged in vitro culture. The objective of this study was to establish a superstimulation protocol that would produce a maximal number of competent COC for standard in vitro embryo production. During experiment 1, eight cyclic Holstein heifers were superstimulated with four doses of FSH. Half the heifers received an injection of LH 6 h before ovum pick-up (OPU). The COC were collected following OPU either 33 or 48 h following the last FSH injection (coasting period). During experiment 2, six cyclic Holstein heifers were superstimulated with six doses of FSH, and in half the heifers, LH was administered 6 h before OPU. The COC were collected following ultrasound-guided transvaginal aspiration of both ovaries 48 h after the last FSH injection (coasting period). The COC originating from follicles with a diameter of 5 mm or more (n = 180 for experiment 1 and 57 for experiment 2) were subjected to standard in vitro maturation, fertilization, and development. When animals were administered four doses of FSH, 48 h of coasting resulted in significantly more 5- to 10-mm follicles (P < 0.01) than 33 h of coasting. If a 33-h coasting period was used, administration of LH 6 h before OPU resulted in a significant increase in both percentage of blastocysts and embryo production rate at Days 7 and 8 (P < or = 0.05) of in vitro culture. If a 48-h coasting period was used, LH injection did not affect the rates of blastocyst production. When donors were administered six doses of FSH with a 48-h coasting period, the highest results, although not significant (P < 0.08), were obtained when animals received LH 6 h before OPU, with 80% +/- 9% (mean +/- SEM) blastocysts and 0.8 +/- 0.09 embryo produced per COC retrieved per heifer at Day 8 of culture. Never has in vitro technology been so close to producing 100% developmentally competent COC.