Embryo Production In Cows Research Articles

Serum concentrations of anti-Müllerian hormone modulate ovarian response to different doses of follicle-stimulating hormone in Japanese Black donors.

Anti-Müllerian hormone (AMH) is a marker for predicting embryo production in cows subjected to superovulation; however, it remains to be established as a reliable predictor of reproductive performance. We hypothesized that the serum AMH concentration of donors affects the ovarian response to follicle-stimulating hormone (FSH) treatment during superovulation. Herein, we retrospectively investigated the association between different FSH doses and AMH concentrations in donor Japanese Black cows in a superovulation program and analyzed the number of total and transferable embryos recovered. The number of transferable embryos recovered from donors with high AMH levels was significantly higher than that recovered from donors with low AMH levels. Additionally, it increased further with a reduction in the FSH dose. These results illustrate that the AMH concentration is a useful marker for predicting embryo production after superovulation, and donors with high AMH levels produce more transferable embryos at low FSH doses than at high doses.

Synchronization of stage of follicle development before OPU improves embryo production in cows with large antral follicle counts

In the present study, there was an evaluation of in vitro embryo production (IVEP) in Bos indicus donor cows with small or large antral follicle counts (AFCs) when there was synchronization of follicular dynamics among cows before ovum pick-up (OPU). Donor cows classified as having small or large AFC were submitted to OPU/IVEP program (Experiment-I) or had follicular-stage synchronization imposed before OPU/IVEP (Experiment-II). In Experiment-I, the cows with a large AFC had a greater (P < 0.01) mean of embryos developing to the blastocyst stage compared to those with a small AFC. In Experiment-II, percentage of viable oocytes/OPU were not affected (P = 0.33) by synchronization of follicular dynamics, but the AFC had an effect (P < 0.0001). There was an interaction (P = 0.01) indicating the larger AFC, with or without imposing of a synchronization treatment regimen, resulted in the most desirable outcome. The number of embryos was affected (P < 0.001) by follicular-stage synchronization and AFC, with there being an interaction (P = 0.002) with the most desirable results for the large AFC-synchronized group. Number of pregnancies was greater (P ≤ 0.02) for recipient females with embryos from synchronized donors and with a large AFC. There was an interaction (P = 0.03) with there being a greater pregnancy percentage for cows with synchronized follicular stages and the large AFC. Bos indicus donor with a large AFC when associated with the synchronization of stage of follicular dynamics pre-OPU results in improvement of the efficacy of IVEP.

Oocyte recovery and in vitro embryo production in cows treated with a single dose of follicle-stimulating hormone

Cows were treated with follicle-stimulating hormone (FSH) in a single dose and then subjected to ovum pick-up (OPU) for evaluation of oocyte recovery and in vitro fertilization (IVF). Cows underwent OPU followed by application of FSH (200 mg) on day 2 and new OPU on day 3. This methodology was repeated 3 times sequentially. In FSH-free the cows (control), OPU was performed at intervals of one week. The number of oocytes recovered was higher in the control cows (22.2 ± 1.5) compared to the treated cows (16.9 ± 1.4; P 0.05). There was no difference between the control cows (47.1 ± 4.2%) and the treated cows (45.3 ± 7.7%) with respect to the percentage of embryos (P > 0.05). There were no differences in pregnancy for the blastocysts between the control and the treated cows (50.0 ± 2.1 and 47.3 ± 2.5%; P > 0.05), respectively. In conclusion, the single-dose FSH protocol did not significantly alter the evaluated results of viable oocytes, in vitro production of embryos, or pregnancy percentage. However, there is a possibility of several consecutive OPU/IVF sessions every three days.

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.

295 SUPEROVULATORY RESPONSE IN COWS FOLLOWING SYNCHRONIZATION OF FOLLICLE WAVE EMERGENCE WITH ESTRADIOL AT DIFFERENT STAGES OF THE ESTROUS CYCLE

Ovarian asynchrony and variability in response to superstimulation remain the most limiting factors in any embryo transfer program (Armstrong D 1993 Theriogenology 39, 7–24). Ovarian response can be increased and less variable if superstimulatory treatment is started at the time of follicular wave emergence (Bö GA et al. 1995 Theriogenology 43, 31–40). A combination of progesterone (P4) and estradiol have been used to synchronize follicular wave for superstimulation. A retrospective analysis was done to compare the ovarian response, superovulatory response and embryo production of cows in Argentina that received progesterone and estradol prior to superstimulation at different stages of the estrous cycle. This research was carried out using different breed of donors (n = 584, 88% Angus) during the last 4 years in Buenos Aires province, Argentina. Heat detection was performed twice a day. At random stages of the estrous cycle, donors received an intravaginal progesterone device (DIB; Syntex, Buenos Aires, Argentina), 2 mg of estradiol benzoate and 50 mg of progesterone (Syntex, Buenos Aires, Argentina) IM on the same day. On day 4 after DIB insertion, superestimulatory treatment was initiated on a decreasing dose regimen of FSH (Pluset; Callier, Spain, or Folltropin, Bioniche Animal Health Inc., Belleville, Ontario, Canada) as IM injections every 12 h over 4 d. On day 6, DIBs were removed, and cows received two doses of 2 mL of cloprostenol 12 h apart. At heat detection, all donors received a dose of 2 mL of GnRH (Dalmarelin; Fatro Von Franken, Buenos Aires, Argentina) by IM injection and were inseminated 12 and 24 h later. Seven days later, embryo collection was performed and ovarian response was evaluated as number of CL + unovulated follicles by transrectal ultrasound using a 7.5-MHz transducer (Pie Medical, Maastricht, the Netherlands). Ova/embryos were evaluated and classified according to the IETS manual. Donors were assigned to receive DIB and estradiol during the following stages of the cycle: group 1: between days 4 and 7 post-estrus (dominant follicle period), group 2: between days 8 and 12 post-estrus (emergence of the second follicular wave), and group 3: between days 13 and 21 post-estrus (dominant follicle of the second wave). Kruskal-Wallis test was used to compare variables among groups, and results are shown in Table 1. Ovarian response as CL + unovulated follicles and number of ovulations were significantly different among groups (P &lt; 0.05). However, there was no significant difference in the number of fertilized ova or transferable embryos. Nevertheless, numeric differences that show that group 2 (started between days 8 and 12 post-estrus) was always superior for all variables. In conclusion, data suggest that estradiol may be more effective in synchronizing follicle wave emergence for superstimulation during the mid-part of the estrous cycle. Table 1. Superovulatory response in cows in which follicle wave emergence was synchronized with estradiol at different stages of the estrous cycle (mean ± SD) Research supported by Centro Genetico Bovino Eolia S.A.

Efeito da estrutura ovárica e da idade de bovinos da raça Holstein Friesian na quantidade e qualidade de ovócitos e de embriões produzidos in vitro

O objetivo do presente trabalho, foi o estudo dos efeitos da idade e da fase do ciclo estral dos bovinos na quantidade e qualidade de ovócitos e de embriões produzidos in vitro. Para isso, foram utilizados ovócitos de 63 vacas da raça Holstein-Friesian abatidas em matadouro, com idades compreendidas entre 1 e 15 anos, as quais foram divididas em 5 lotes de acordo com a idade. Cada lote foi subdividido de acordo com a fase do ciclo estral em que o animal se encontrava no dia do abate, pela presença ou não de corpo lúteo funcional na superfície do ovário. Os lotes referentes à idade foram: ;8 anos. Após punção dos folículos, os ovócitos foram divididos nas classes A, B, C e D, tendo em conta o seu aspecto morfológico, em que apenas os de classe A e B foram usados para a FIV. Observou-se que o número de ovócitos produzidos foi diretamente proporcional à idade das vacas (R=0,99 - P&lt;0,001). Quanto à fase do ciclo estral, as vacas em fase luteínica, produziram maior número de ovócitos que as vacas em fase folicular (P&lt;0,001), respetivamente 7,05 ± 0,11 e 10,87 ± 1,01. Relativamente à qualidade dos ovócitos em função da idade das vacas, observou-se uma correlação positiva (R = 0,94 p&lt;0,01) até aos [7, 8] anos, começando a baixar a partir desta idade. As vacas em fase luteínica produziram ovócitos de melhor qualidade relativamente às vacas em fase folicular (6,77 ± 0,64 e 3,84± 0,64; respetivamente). Quanto à quantidade de zigotos que clivaram, esta foi superior para os lotes de vacas em fase luteínica em comparação com os de vacas em fase folicular (59,03% e 45,52%; respetivamente), observando-se ainda que as vacas em fase luteínica produziram igualmente, em geral, maior número de embriões aos 7 dias após FIV que as vacas em fase folicular(44,23% e 31,48%; respetivamente). Os resultados do presente trabalho permitem concluir que existe uma estreita relação entre a idade e a fase do ciclo estral das vacas e a quantidade e qualidade dos ovócitos e de embriões produzidos in vitro.

Ovum pick up and in vitro embryo production in cows superstimulated with an individually adapted superstimulation protocol

The aim of this experiment was to apply an ovarian superstimulation protocol prior to ovum pick up (OPU), tailored to the individual donor response, to evaluate its advantages and disadvantages in terms of follicle numbers and diameters, the numbers of retrieved oocytes and day 7 cultured blastocysts. Ten adult non-lactating dairy cows were superstimulated with pFSH and subjected to ovum pick up-in vitro fertilisation (OPU-IVF) 6 times at 2-week intervals. On day 0 of each 2-week period, all follicles >8 mm were ablated and an ear implant (Crestar ®, Intervet, Belgium) was inserted. On day 2, 48 h after follicle ablation the animals were administered six equal doses of pFSH, divided into morning and evening doses for 3 days. On day 7, 48 h following the last pFSH injection, follicle diameters were measured by ultrasound and all follicles were subjected to OPU. All cumulus-oocyte complexes (COC), regardless of their quality, were subjected to in vitro maturation-in vitro fertilisation-in vitro culture (IVM-IVF-IVC). The total dose of pFSH prior to the first OPU session was 300 μg per animal. During the following OPU sessions, the total pFSH dose was either kept unchanged, increased or reduced (±50 μg), according to the percentage of follicles of more than 11 mm in diameter, present in the previous session of that particular donor. The mean number of punctured follicles per session was 11.9 ± 7.7 (mean ± S.D.), with 16% of follicles exceeding 11 mm. These follicles yielded a mean of 5.6 ± 4.1 cumulus oocyte complexes (COC), 32% of which had ≥3 layers of cumulus cells (quality 1 and 2). The recovery rate was 47%. Finally, all COC were subjected to IVM-IVF-IVC, which resulted in a mean of 2.0 ± 2.3 blastocysts on day 7 postinsemination. The subtle changes in pFSH dose influenced the sizes but not the numbers of follicles, the latter parameter was influenced by the individual donor and the OPU session.

Evidence of oocyte donor cow effect over oocyte production and embryo development in vitro

There have been few studies on a possible maternal influence on in vitro embryo production in cows. The objective of this study was to evaluate the maternal influence on oocyte production and in vitro blastocyst formation rate using repeated ovum pick-up and in vitro fertilization. Six contemporary cows raised on the same farm and with varied genetic origins were submitted to 42 weeks of ovum pick-up organized into four series. Collected oocytes were fertilized in vitro with spermatozoa from a different bull for each series. In total, 1933 oocytes were recovered from 3936 follicles with a recovery rate of 57.2% and a mean oocyte collection of 4.6+/-0.2 (mean+/-SEM) per animal per session. Animals were ranked according to their oocyte production. The best oocyte donor was the same female in all four series. No relationship was identified between oocyte production and blastocyst production rate (r=-0.08). The mean blastocyst rate was 28.8% with significant variation among animals. The best and the worst blastocyst producers were always the same animals independent of the semen used. The results of the present study support the hypothesis that in cattle, the oocyte donor influences the production of blastocysts. Furthermore, they demonstrate that oocyte and embryo production are independent factors. Further studies are necessary to identify the maternal or oocyte factors responsible for such differences.

Evidence of oocyte donor cow effect over oocyte production and embryo development in vitro

There have been few studies on a possible maternal influence on in vitro embryo production in cows. The objective of this study was to evaluate the maternal influence on oocyte production and in vitro blastocyst formation rate using repeated ovum pick-up and in vitro fertilization. Six contemporary cows raised on the same farm and with varied genetic origins were submitted to 42 weeks of ovum pick-up organized into four series. Collected oocytes were fertilized in vitro with spermatozoa from a different bull for each series. In total, 1933 oocytes were recovered from 3936 follicles with a recovery rate of 57.2% and a mean oocyte collection of 4.6+/-0.2 (mean+/-SEM) per animal per session. Animals were ranked according to their oocyte production. The best oocyte donor was the same female in all four series. No relationship was identified between oocyte production and blastocyst production rate (r=-0.08). The mean blastocyst rate was 28.8% with significant variation among animals. The best and the worst blastocyst producers were always the same animals independent of the semen used. The results of the present study support the hypothesis that in cattle, the oocyte donor influences the production of blastocysts. Furthermore, they demonstrate that oocyte and embryo production are independent factors. Further studies are necessary to identify the maternal or oocyte factors responsible for such differences.