Influencia de la suplementación del medio de cultivo con ácido linoleico en la supervivencia a la congelación de embriones bovinos

Studies report that the addition of linoleic acid to bovine embryo production media in vitro improves its resistance to conventional freezing. In this study the effect on survival of in vitro bovine embryos under freezing was evaluated by the addition of linoleic acid (LA) in the culture medium on days 3 or 5. A total of 1452 oocytes were recovered and assigned to 4 experimental groups and a control group. Six replicates were made to obtain approximately 100 freeze-thawed embryos per group. Group 1: 100 M on Day 3, group 2: 50 M on Day 3, group 3: 100 M on Day 5, group 4: 50 M on Day 5. The embryos were frozen and one week after they were thawed to evaluate the percentages of re-expansion (24 h) and hatching (72 h). The results were analyzed by ANOVA and when the differences were significant, the means between the groups were compared by Fischer's LSD Test (p <0.05). It was observed that the percentage of re-expansion was significantly improved with the addition of 50 μM LA on Day 5 (54.94 ± 28.8 vs. 19.19 ± 28.4, p = 0.001) and the percentage of hatching with the addition of 50 μM of LA at day 3 (37.9 ± 18.3 vs. 9.02 ± 12.0, p = 0.014), when them were compared with the control group. In conclusion, the addition of linoleic acid improves the survival to freezing of bovine embryos produced by in vitro techniquesEstudios reportan que la adición de ácido linoleico en los medios de producción de embriones bovinos in vitro, mejora su resistencia a la congelación convencional. En este estudio se evaluó el efecto en la supervivencia de embriones bovinos in vitro a la congelación, mediante la adición de ácido linoleico (LA) en el medio de cultivo los días 3 o 5. Un total de 1452 oocitos fueron recuperados y asignados a 4 grupos experimentales y un grupo control. Se realizaron seis réplicas, para obtener aproximadamente 100 embriones congelables por grupo. Grupo 1: 100 M en Día 3, grupo 2: 50 M en Día 3, grupo 3: 100 M en Día 5, grupo 4: 50 M en Día 5. Los embriones se congelaron y a la semana fueron descongelados para evaluar los porcentajes de re-expansión (24 h) y de eclosión (72 h). Los resultados fueron analizados mediante ANOVA y cuando las diferencias fueron significativas, se compararon las medias entre los grupos por el Test LSD de Fischer (p < 0.05). Se observó que el porcentaje de re-expansión mejoró significativamente con la adición de 50 M de LA en el Día 5 (54.94 ± 28.8 vs. 19.19 ± 28.4, p = 0.001) y el porcentaje de eclosión con la adición de 50 M de LA en el Día 3 (37.9 ± 18.3 vs. 9.02 ± 12.0, p = 0.014), cuando se comparó con el grupo control. En conclusión, la adición de ácido linoleico mejora la supervivencia a la congelación de los embriones bovinos producidos mediante técnicas in vitrFil: Bernal Ballesteros, Beatriz H.. Instituto de Reproducción Animal Córdoba; Argentina. Vitrogen Colombia S.A.S; ColombiaFil: Tribulo, Humberto Elias. Instituto de Reproducción Animal Córdoba; ArgentinaFil: Mutto, Adrián Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Bo, Gabriel Amilcar. Instituto de Reproducción Animal Córdoba; Argentina. Universidad Nacional de Villa María; Argentin

New Tools for in Vitro Handling and Selection of Cryopreserved Sperm Samples in Equines

Cryopreserved sperm (SPZ) are used widely in domestic animals for assisted reproduction techniques (ART). However, cryopreservation procedures negatively affect SPZ quality, causing changes at the structural and molecular levels. Therefore, using cryopreserved SPZ for ART can decrease the efficiency of these techniques as well as the quality of the embryos obtained, being necessary to optimize the handling of this type of sample. Particularly in equines, ICSI is the most used technique for low-quality equine semen samples where SPZ is selected based on their motility and morphology. Physiologically, the oviduct epithelial cells (OEC) are involved in the selection of a population of SPZ suitable for oocyte fertilization, which is released from the oviduct due to the capacitation process. This work aimed to evaluate different conditions for the in vitro manipulation and incubation of equine cryopreserved SPZ and to establish an in vitro OEC culture to select an SPZ population with fertilizing capacity suitable for its use in ART in this species.Regarding the handling and the effect on the motility of post-thawed equine cryopreserved SPZ samples, we used non-capacitating Whitten´s medium, less effect on motility was observed through the time (120 min) when SPZ were incubated at concentrations of 30 mill/ml compared to lower concentrated samples (CASA, p<0.05). Also, the motility decreased by half with centrifugations at 200g longer than 1 min (p<0.05). On the other hand, we have established a culture model of OECs in vitro, in which we demonstrated the expression of epithelial markers (E-cadherin and cytokeratin) by both RT-PCR and immunofluorescence (IF). When we performed SPZ-OEC cocultures, we observed that the attached SPZs were motile and presented intact acrosome (PSA-FITC, IF), suggesting a selection by the oviductal model. Then, the co-cultures were incubated in capacitating conditions (capacitating Whitten´s medium) and the released SPZ population was recovered. Under these conditions, a greater number of live sperm (Hoechst258 assessed by IF), capacitated (activation of PKA and phosphorylation on tyrosine residues by IF), with progressive motility (CASA) and with the intact acrosome (PSA-FITC, IF) compared to the control was observed (p<0.05). Moreover, the decrease in motility through the time was less in these SPZ than in the cryopreserved SPZ incubated in the absence of OECs. This sperm population could be recovered for its use in different ART.Improvements in handling and selection of cryopreserved SPZ not only generate tools to solve the problem that IVF presents in equines, but would also improve efficiency in other ART such as ICSI, allowing the use of a population of higher quality gametes which it would positively impact the quality of the embryos obtained.Fil: Laiz Quiroga, Lucía Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Gimeno, Brenda Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; ArgentinaFil: Martínez León, Eduardo Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; ArgentinaFil: Von Meyeren, Micaela. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Mutto, Adrián Angel. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Bariani, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Centro de Estudios Farmacológicos y Botánicos. Universidad de Buenos Aires. Facultad de Medicina. Centro de Estudios Farmacológicos y Botánicos; ArgentinaFil: Osycka Salut, Claudia Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Centro de Estudios Farmacológicos y Botánicos. Universidad de Buenos Aires. Facultad de Medicina. Centro de Estudios Farmacológicos y Botánicos; ArgentinaIV Joint Meeting of The Biology Societies of ArgentinaMendozaArgentinaSociedad de Biología de CuyoSociedad Argentina de BiologíaSociedad de Biología de CórdobaSociedad de Biología de RosarioAsociación de Biología de Tucumá

Effects of in vitro interactions of oviduct epithelial cells with frozen–thawed stallion spermatozoa on their motility, viability and capacitation status

Cryopreservation by negatively affecting sperm quality decreases the efficiency of assisted reproduction techniques (ARTs). Thus, we first evaluated sperm motility at different conditions for the manipulation of equine cryopreserved spermatozoa. Higher motility was observed when spermatozoa were incubated for 30 min at 30 × 106 /mL compared to lower concentrations (p < 0.05) and when a short centrifugation at 200× g was performed (p < 0.05). Moreover, because sperm suitable for oocyte fertilization is released from oviduct epithelial cells (OECs), in response to the capacitation process, we established an in vitro OEC culture model to select a sperm population with potential fertilizing capacity in this species. We demonstrated E-cadherin and cytokeratin expression in cultures of OECs obtained. When sperm–OEC cocultures were performed, the attached spermatozoa were motile and presented an intact acrosome, suggesting a selection by the oviductal model. When co-cultures were incubated in capacitating conditions a greater number of alive (p < 0.05), capacitated (p < 0.05), with progressive motility (p < 0.05) and with the intact acrosome sperm population was observed (p < 0.05) suggesting that the sperm population released from OECs in vitro presents potential fertilizing capacity. Improvements in handling and selection of cryopreserved sperm would improve efficiencies in ARTs allowing the use of a population of higher-quality sperm.Fil: Gimeno, Brenda Florencia. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Bariani, Maria Victoria. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Laiz Quiroga, Lucía Belén. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Martínez León, Eduardo Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; ArgentinaFil: Von Meyeren, Micaela. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Rey, Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; ArgentinaFil: Mutto, Adrián Angel. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Osycka Salut, Claudia Elena. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; Argentin

Detection of recombinant human lactoferrin and lysozyme produced in a bitransgenic cow

Lactoferrin and lysozyme are 2 glycoproteins with great antimicrobial activity, being part of the nonspecific defensive system of human milk, though their use in commercial products is difficult because human milk is a limited source. Therefore, many investigations have been carried out to produce those proteins in biological systems, such as bacteria, yeasts, or plants. Mammals seem to be more suitable as expression systems for human proteins, however, especially for those that are glycosylated. In the present study, we developed a bicistronic commercial vector containing a goat β-casein promoter and an internal ribosome entry site fragment between the human lactoferrin and human lysozyme genes to allow the introduction of both genes into bovine adult fibroblasts in a single transfection. Embryos were obtained by somatic cell nuclear transfer, and, after 6 transferences to recipients, 3 pregnancies and 1 viable bitransgenic calf were obtained. The presence of the vector was confirmed by fluorescent in situ hybridization of skin cells. At 13 mo of life and after artificial induction of lactation, both recombinant proteins were found in the colostrum and milk of the bitransgenic calf. Human lactoferrin concentration in the colostrum was 0.0098 mg/mL and that in milk was 0.011 mg/mL; human lysozyme concentration in the colostrum was 0.0022 mg/mL and that in milk was 0.0024 mg/mL. The molar concentration of both human proteins revealed no differences in protein production of the internal ribosome entry site upstream and downstream protein. The enzymatic activity of lysozyme in the transgenic milk was comparable to that of human milk, being 6 and 10 times higher than that of bovine lysozyme presentin milk. This work represents an important step to obtain multiple proteins or enhance single protein production by using animal pharming and fewer regulatory and antibiotic-resistant foreign sequences, allowing the design of humanized milk with added biological value for newborn nutrition and development. Transgenic animals can offer a unique opportunity to the dairy industry, providing starting materials suitable to develop specific products with high added value. Key words: bitransgenic cow, human lactoferrin, ELISA, human lysozyme.Fil: Kaiser, German Gustavo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Grupo de Biotecnología de la Reproducción; ArgentinaFil: Mucci, Nicolas Crescencio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Grupo de Biotecnología de la Reproducción; ArgentinaFil: Gonzalez, Vega. Universidad de Zaragoza. Facultad de Veterinaria. Tecnología de los Alimentos; EspañaFil: Sánchez, Lourdes. Universidad de Zaragoza. Facultad de Veterinaria. Tecnología de los Alimentos; EspañaFil: Parrón, José Antonio. Universidad de Zaragoza. Facultad de Veterinaria. Tecnología de los Alimentos; EspañaFil: Pérez, María Dolores. Universidad de Zaragoza. Facultad de Veterinaria. Tecnología de los Alimentos; EspañaFil: Calvo, Miguel. Universidad de Zaragoza. Facultad de Veterinaria. Tecnología de los Alimentos; EspañaFil: Aller Atucha, Juan Florencio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Grupo de Biotecnología de la Reproducción; ArgentinaFil: Hozbor, Federico Andres. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Grupo de Biotecnología de la Reproducción; ArgentinaFil: Mutto, Adrián Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; Argentin

CRISPR-on system for the activation of the endogenous human INS gene

Advances in the field of epigenetics have allowed the design of new therapeutic strategies to address complex diseases such as type 1 diabetes (T1D). Clustered regularly interspaced short palindromic repeats (CRISPR)-on is a novel and powerful RNA-guided transcriptional activator system that can turn on specific gene expression; however, it remains unclear whether this system can be widely used or whether its use will be restricted depending on cell types, methylation promoter statuses or the capacity to modulate chromatin state. Our results revealed that the CRISPR-on system fused with transcriptional activators (dCas9-VP160) activated endogenous human INS, which is a silenced gene with a fully methylated promoter. Similarly, we observed a synergistic effect on gene activation when multiple single guide RNAs were used, and the transcriptional activation was maintained until day 21. Regarding the epigenetic profile, the targeted promoter gene did not exhibit alteration in its methylation status but rather exhibited altered levels of H3K9ac following treatment. Importantly, we showed that dCas9-VP160 acts on patients' cells in vitro, particularly the fibroblasts of patients with T1D.Fil: Giménez, Carla Alejandra. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ielpi, Marcelo. Hospital Italiano; ArgentinaFil: Mutto, Adrián Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Grosembacher, Luis. Hospital Italiano; ArgentinaFil: Argibay, Pablo. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pereyra Bonnet, Federico Alberto. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

2 Role of histone H3 lysine 9 trimethylation during bovine pre-implantation embryonic development

Histones play an important role in DNA’s compaction and organisation into the cellular nucleus. Depending on which histone modification occurs, chromatin can take a conformation of heterochromatin or euchromatin, which are associated with gene repression or expression, respectively. Histone H3 lysine 9 (H3K9) trimethylation (H3K9me3) is associated with gene silencing. At least 3 methyltransferases are able to change the methylation status of H3K9: SUV39H1, SUV39H2, and SETDB1. In several mammalian species, modulation of H3K9 methylation status has been demonstrated to be necessary to achieve a successful pre-implantation embryonic development after IVF or somatic cell NT. The aim of this work was to study the role of H3K9me3 in IVF pre-implantation bovine embryos. For this purpose, immunostaining of H3K9me3 at different pre-implantation stages of development was performed. Further, the relative abundances of the methyltransferases SUV39H1 and SUV39H2 were measured by real-time PCR using luciferase transcript as an exogenous gene for normalization. Finally, to evaluate H3K9me3 involvement during pre-implantation embryonic development, we generated SUV39H1 or SUV39H2 knockout embryos by the CRISPR/Cas9 system. We designed guide RNA targeting SUV39H1 or SUV39H2 and co-injected the presumptive zygote’s cytoplasm 18 h post-fertilization with Cas9 protein. At Day 8 post-fertilization, the number of blastocysts was assessed and embryos were immunostained to evaluate H3K9me3. Results were analysed using Student’s t-test or ANOVA with the post-hoc Tukey test depending on data set (P ≤ 0.05) and reported as means ± standard errors of the mean. Oocytes at germinal vesicle stage and metaphase II as well as embryos at different stages of pre-implantation development (2, 4, and 8 cells, morula, and blastocyst; n = 6) were immunoreactive for H3K9me3. Expression of SUV39H1 and SUV39H2 mRNA decreased significantly as embryonic development progressed, reaching undetectable levels at stages where genome activation had already occurred (morula and blastocyst; P < 0.0001, n = 3). When zygotes were co-injected with the guide RNA targeting SUV39H1/Cas9, embryonic production showed a significant increase compared with the control [42.26% ± 5.03 (28/65) v. 23.86% ± 3.99 (21/88), respectively; P = 0.034, n = 4], and H3K9me3 immunostaining was reduced in treated embryos. Editing efficiency was estimated at 66%. In contrast, no statistical differences were found in embryonic production or H3K9me3 immunostaining in embryos co-injected with the guide RNA targeting SUV39H2/Cas9 (P = 0.57, n = 3). In conclusion, we were able to characterise H3K9me3 and determine transcript levels of methyltransferases SUV39H1 and SUV39H2 in oocytes and different stages of pre-implantation embryonic development. We also demonstrated that SUV39H1 deletion led to an increased embryonic production, suggesting that H3K9me3 removal would allow a greater relaxation of the heterochromatin and consequently a successful activation of embryonic genes. This highlights the essential role of H3K9me3 during bovine pre-implantation embryonic development.Fil: Navarro, Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Bluguermann, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Von Meyeren, Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Bariani, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Osycka Salut, Claudia Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Mutto, Adrián Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; Argentina45th Annual Conference of the IETS (International Embryo Technology Society)Nueva OrleansEstados UnidosInternational Embryo Technology Societ

Expression profile of genes as indicators of developmental competence and quality of in vitro fertilization and somatic cell nuclear transfer bovine embryos.

Reproductive biotechnologies such as in vitro fertilization (IVF) and somatic cell nuclear transfer (SCNT) enable improved reproductive efficiency of animals. However, the birth rate of in vitro-derived embryos still lags behind that of their in vivo counterparts. Thus, it is critical to develop an accurate evaluation and prediction system of embryo competence, both for commercial purposes and for scientific research. Previous works have demonstrated that in vitro culture systems induce alterations in the relative abundance (RA) of diverse transcripts and thus compromise embryo quality. The aim of this work was to analyze the RA of a set of genes involved in cellular stress (heat shock protein 70-kDa, HSP70), endoplasmic reticulum (ER) stress (immunoglobulin heavy chain binding protein, Bip; proteasome subunit β5, PSMB5) and apoptosis (BCL-2 associated X protein, Bax; cysteine aspartate protease-3, Caspase-3) in bovine blastocysts produced by IVF or SCNT and compare it with that of their in vivo counterparts. Poly (A) + mRNA was isolated from three pools of 10 blastocysts per treatment and analyzed by real-time RT-PCR. The RA of three of the stress indicators analyzed (Bax, PSMB5 and Bip) was significantly increased in SCNT embryos as compared with that of in vivo-derived blastocysts. No significant differences were found in the RA of HSP70 and Caspase-3 gene transcripts. This study could potentially complement morphological analyses in the development of an effective and accurate technique for the diagnosis of embryo quality, ultimately aiding to improve the efficiency of assisted reproductive techniques (ART)

Superovulation, embryo recovery, and pregnancy rates from seasonally anovulatory donor mares treated with recombinant equine FSH (reFSH)

The effectiveness of different treatments with recombinant equine FSH to stimulate follicular growth, multiple ovulations and embryo production in seasonally anovulatory mares was evaluated. During mid-winter season (July–August in Argentina, South America) forty light breed donor mares, presenting follicles 35 mm). Ovulations were detected in 80% of mares in Groups 1 and 2, 50% of mares in Group 3 and in none of Group 4 (Control). Among ovulating mares, no differences in number of ovulations, number of embryos recovered, or pregnancy rates were observed among reFSH treatments. Of treated mares, 6, 7, and 5 produced embryos in Groups 1, 2, and 3, respectively. The average embryo recovery rate per ovulated mare was 88%. The average embryo recovery rate per ovulation was 43%. Overall, a 59% pregnancy rate was achieved. These results indicate that treatment with reFSH during deep anestrus results in follicular development, ovulation of fertile oocytes, and production of embryos that established viable pregnancies after transfer. Also, a single daily administration of reFSH was as effective as two daily administrations, which allows for a simplified administration regimen.Fil: Roser, Janet F.. University of California at Davis; Estados UnidosFil: Etcharren, Maria V.. Universidad Nacional de Río Cuarto; ArgentinaFil: Miragaya, Marcelo H.. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias; ArgentinaFil: Mutto, Adrián Angel. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Colgin, Mark. No especifíca;Fil: Ross, Pablo J.. Universidad Nacional de Río Cuarto; ArgentinaFil: Ross, Pablo J.. University of California at Davis; Estados Unido