Embryo production: alternative methods

Hormonal treatments for increasing the oocyte and embryo production in an OPU–IVP system

The objective was to enhance the inherent developmental ability of bovine oocytes retrieved by ultrasound-guided transvaginal aspiration. Various hormonal regimes were utilized to produce partially matured oocytes in vivo, in order to improve embryo development following IVF. In the first experiment, a two-by-two factorial design was used with FSH (multiple versus single dose) and im administration of LH (yes versus no) 6h prior to OPU. In all protocols (which lasted for nine consecutive weeks), ovarian stimulation was performed in the presence of a CIDR. One FSH administration was adequate for ovarian stimulation (9.33+/-0.7 and 10.14+/-0.7 follicles per cow per OPU session); however, multiple injections increased (P<0.05) follicular response (12.97+/-0.7 and 13.97+/-0.7). In the second experiment, a two-by-two factorial design was used to compare the effects, during ovarian stimulation, of the presence or absence of CIDR, and iv treatment with LH 6h prior to OPU (yes versus no), on oocyte competence (judged by blastocyst development rates following IVF). Presence of CIDR during superstimulation had no effect on the follicular response. Administration of LH 6h prior to OPU increased (P<0.05) the oocytes of higher morphological grades, and in the absence of a CIDR, improved (P<0.05) blastocyst development rate. Treatment with LH, 6h prior to OPU without the use of CIDR during ovarian stimulation, resulted in 2.89+/-0.4 blastocysts per cow per OPU session as compared to 1.56+/-0.4, 1.56+/-0.4 and 1.33+/-0.4 for all other groups. In conclusion, compared to single administration, multiple FSH administration increased (P<0.05) available follicles for aspiration. Moreover, when ovarian stimulation in the absence of CIDR was followed by administration of LH 6h prior to OPU, it increased (P<0.05) the number of blastocysts per OPU session.

Reproductive biology in the era of genomics biology

Current and emerging technologies in reproductive biology, including assisted reproductive technologies and animal cloning, are discussed in the context of the impact of genomics era biology. The discussion focuses on the endocrinology associated with establishment and maintenance of pregnancy, fetal-placental development, lactation, and neonatal survival. Various aspects of uterine biology, including development during the neonatal period and function in adult females, are discussed with respect to reproductive efficiency. It is clear that combining strategies for use of conventional animal models for studying the reproductive system with new genomics technologies will provide exceptional opportunities in discovery research involving data integration and application of functional genomics to benefit animal agriculture and the biomedical community. New and emerging biotechnologies and comparative genomics approaches will greatly advance our understanding of genes that are critical to development of the reproductive system and to key events at each stage of the reproductive cycle of females and males.

Embryo recovery and pregnancy rates after the delay of ovulation and fixed time insemination in superstimulated beef cows

The aim of this study was to evaluate the effect of delaying ovulation subsequent to superstimulation of follicular growth in beef cows (Bos indicus) on embryo recovery rates and the capacity of embryos to establish pregnancies. Ovulation was delayed by three treatments using either progesterone (CIDR-B) or a GnRH agonist (deslorelin). Multiparous Nelore cows (n = 24) received three of four superstimulation treatments in an incomplete block design (n = 18 per group). Cows in Groups CTRL, P48 and P60 were treated with a CIDR-B device plus estradiol benzoate (EB, 4 mg, i.m.) on Day-5, while cows in Group D60 were implanted with deslorelin on Day-7. Cows were superstimulated with FSH (Folltropin-V, 200 mg), from Day 0 to 3, using twice daily injections in decreasing amounts. All cows were treated with a luteolytic dose of prostaglandin on Day 2 (08:00 h). CIDR-B devices were removed as follows: Group CTRL, Day 2 (20:00 h); Group P48, Day 4 (08:00 h); Group P60, Day 4 (20:00 h). Cows in Group CTRL were inseminated at 10, 20 and 30 h after first detected estrus. Ovulation was induced for cows in Group P48 (Day 4, 08:00 h) and Groups P60 and D60 (Day 4, 20:00 h) by injection of LH (Lutropin, 25 mg, i.m.), and these cows were inseminated 10 and 20 h after treatment with LH. Embryos were recovered on Days 11 or 12, graded and transferred to synchronized recipients. Pregnancies were determined by ultrasonography around Day 100. Data were analyzed by mixed procedure, Kruskal-Wallis and Chi-square tests. The number of ova/embryos, transferable embryos (mean +/- SEM) and pregnancy rates (%) were as follows, respectively: Group CTRL (10.8+/-1.8, 6.1+/-1.3, 51.5), P48 (12.6+/-1.9, 7.1+/-1.0, 52.3), P60 (10.5+/-1.6, 5.7+/-1.3, 40.0) and D60 (10.3+/-1.7, 5.0+/-1.2, 50.0). There were no significant differences among the groups (P > 0.05). It was concluded that fixed time AI in association with induced ovulation did not influence embryo recovery. Furthermore, pregnancy rates in embryos recovered from cows with delayed ovulation were similar to those in embryos obtained from cows treated with a conventional superstimulation protocol.

Embryo transfer in Bos indicus cattle

In the present short review superovulation treatments commonly used for Bos taurus and/or Bos indicus will be addressed with emphasis in recent superstimulation protocols associated with pharmacological manipulation of the follicular dynamics to improve donor management and potentially embryo yield. Results obtained after superovulation treatments in which the time of LH surge is selectively delayed as an attempt to improve embryo yield are presented and discussed.

Use of a GnRH agonist to prevent the endogenous LH surge and injection of exogenous LH to induce ovulation in heifers superstimulated with FSH: A new model for superovulation

A new protocol for superovulating cattle which allows for control of the timing of ovulation after superstimulation with FSH was developed. The preovulatory LH surge was blocked with the GnRH agonist deslorelin, and ovulation was induced by injection of LH. In Experiment 1, heifers (3-yr-old) were assigned to a control group (Group 1A, n = 4) or a group with deslorelin implants (Group 1B, n = 5). On Day -7, heifers in Group 1A received a progestagen CIDR-B((R))device, while heifers in Group 1B received a CIDR-B((R))device + deslorelin implants. Both groups were superstimulated with twice daily injections of FSH (Folltropin((R))-V): Day 0, 40 mg (80 mg total dose on Day 0); Day 1, 30 mg; Day 2, 20 mg; Day 3, 10 mg. On Day 2, heifers were given PGF (a.m.) and CIDR-B((R)) devices were removed (p.m.). Three heifers in Group 1A had a LH surge and ovulated, whereas neither of these events occurred in Group 1B (with deslorelin implants) heifers. In Experiment 2, heifers (3-yr-old) were assigned to 1 of 4 equal groups (n = 6). On Day -7, heifers in Group 2A received a norgestomet implant, while heifers in Groups 2B, 2C and 2D received norgestomet + deslorelin implants. Heifers were superstimulated with FSH starting on Day 0 as in Experiment 1. On Day 2, heifers were given PGF (a.m.) and norgestomet implants were removed (p.m.). Heifers in Groups 2B to 2D were given 25 mg LH (Lutropin((R))): Group 2B, Day 4 (a.m.); Group 2C, Day 4 (p.m.); Group 2D, Day 5 (a.m.). Heifers in Group 2A were inseminated at estrus and 12 and 24 h later, while heifers in Groups 2B to 2D were inseminated at the time of respective LH injection and 12 and 24 h later. Injection of LH induced ovulation in heifers in Groups 2B to 2D. Heifers in Group 2C had similar total ova and embryos (15.2 +/- 1.4) as heifers in Group 2A (11.0 +/- 2.8) but greater (P < 0.05) numbers than heifers in Group 2B (7.0 +/- 2.3) and Group 2D (6.3 +/- 2.0). The number of transferable embryos was similar for heifers in Group 2A (5.8 +/- 1.8) and Group 2C (7.3 +/- 2.1) but lower (P < 0.05) for heifers in Group 2B (1.2 +/- 0.8) and Group 2D (1.3 +/- 1.0). The new GnRH agonist-LH protocol does not require observation of estrus, and induces ovulation in superstimulated heifers that would not have an endogenous LH surge.

Influence of varied progestogen treatments on ovarian follicle status and subsequent ovarian superstimulatory responses in cows

The influence of ovarian follicle status and follicle dominance on the response to superstimulatory treatment with FSH was examined in cows. In Experiment 1, oestrus was synchronised using Crestar and on Days 4-6 of the ensuing oestrous cycle cows were assigned to: Group NO (n = 9), control, endogenous CL and no treatment; Group N1 (n = 15), injected with a luteolytic dose of cloprostenol (500 micrograms) and implanted with one implant (3 mg) of the synthetic progestogen, norgestomet; Group N8 (n = 18), injected with 500 micrograms cloprostenol and implanted with eight (24 mg) implants of norgestomet. On Days 9-11, seven implants were removed from six cows in Group N8 and these cows, plus eight Group N1 and all Group N0 cows, were superstimulated with porcine FSH (Folltropin-V) over 4 days (360 mg total dose). The remaining implants were removed from cows in Groups N1 and N8 on Days 11-13, and all cows received 500 micrograms cloprostenol. Numbers and sizes of ovarian follicles, and CL, were recorded by trans-rectal ultrasonography; the largest follicle > 10 mm in diameter was considered morphologically dominant (DF). On Days 9-11, the proportions of cows with a DF were: Group N0, 3/9; Group N1, 14/15; Group N8, 0/18. Total follicles on the 4th day of FSH treatment were greater (P < 0.05) for cows in Group N1 (21.6 +/- 4.2) compared with Group N0 (10.9 +/- 2.4), with cows in Group N8 (13.2 +/- 0.9) not different from the other two groups. Subsequent numbers of CL were lower (P < 0.05) for cows in Group N1 (5.0 +/- 1.3) compared with Group N0 (9.4 +/- 2.0), with cows in Group N8 (8.5 +/- 1.0) not different from the other two groups. In Experiment 2, oestrus was synchronised in cows and on Days 4-6, cows were assigned to: Group C0 (n = 7), control, endogenous CL and no treatment; Group C3 (n = 6), received three CIDR-B intra-vaginal devices that delivered progesterone. On Days 9-11, two CIDR-B were removed from cows in Group C3 and all cows treated with FSH as in Experiment 1. The remaining CIDR-B was removed from cows in Group C3 on Days 11-13 and all cows injected with 500 micrograms cloprostenol. Proportions of cows with a DF on Days 9-11 and diameter of largest follicle were: Group C0, 6/7 and 12.6 +/- 0.9 mm; Group C3, 2/6 and 9.6 +/- 0.8 mm. Numbers of CL on Day 8 after oestrus were: Group C0, 20.0 +/- 7.1; Group C3, 14.8 +/- 4.8 (P > 0.05). Exposure to low dose norgestomet allowed development of a persistent dominant follicle, resulting in a reduced response to superstimulation with FSH. High dose progestogen restricted follicle growth without apparent effects on responses to superstimulation.