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.     

Somatic cell nuclear transfer alters peri-implantation trophoblast differentiation in bovine embryos

Abnormal placental development limits success in ruminant pregnancies derived from somatic cell nuclear transfer (SCNT), due to reduction in placentome number and consequently, maternal/fetal exchange. In the primary stages of an epithelial-chorial association, the maternal/fetal interface is characterized by progressive endometrial invasion by specialized trophoblast binucleate/giant cells (TGC). We hypothesized that dysfunctional placentation in SCNT pregnancies results from aberration in expression of genes known to be necessary for trophoblast proliferation (Mash2), differentiation (Hand1), and function (IFN-tau and PAG-9). We, therefore, compared the expression of these factors in trophoblast from bovine embryos derived from artificial insemination (AI), in vitro fertilization (IVF), and SCNT prior to (day 17) and following (day 40 of gestation) implantation, as well as TGC densities and function. In preimplantation embryos, Mash2 mRNA was more abundant in SCNT embryos compared to AI, while Hand1 was highest in AI and IVF relative to SCNT embryos. IFN-tau mRNA abundance did not differ among groups. PAG-9 mRNA was undetectable in SCNT embryos, present in IVF embryos and highest in AI embryos. In postimplantation pregnancies, SCNT fetal cotyledons displayed higher Mash2 and Hand1 than AI and IVF tissues. Allelic expression of Mash2 was not different among the groups, which suggests that elevated mRNA expression was not due to altered imprinting status of Mash2. The day 40 SCNT cotyledons had the fewest number of TGC compared to IVF and AI controls. Thus, expression of genes critical to normal placental development is altered in SCNT bovine embryos, and this is expected to cause abnormal trophoblast differentiation and contribute to pregnancy loss.     

Rabbit somatic cell cloning: effects of donor cell type, histone acetylation status and chimeric embryo complementation

The epigenetic status of a donor nucleus has an important effect on the developmental potential of embryos produced by somatic cell nuclear transfer (SCNT). In this study, we transferred cultured rabbit cumulus cells (RCC) and fetal fibroblasts (RFF) from genetically marked rabbits (Alicia/Basilea) into metaphase II oocytes and analyzed the levels of histone H3-lysine 9-lysine 14 acetylation (acH3K9/14) in donor cells and cloned embryos. We also assessed the correlation between the histone acetylation status of donor cells and cloned embryos and their developmental potential. To test whether alteration of the histone acetylation status affects development of cloned embryos, we treated donor cells with sodium butyrate (NaBu), a histone deacetylase inhibitor. Further, we tried to improve cloning efficiency by chimeric complementation of cloned embryos with blastomeres from in vivo fertilized or parthenogenetic embryos. The levels of acH3K9/14 were higher in RCCs than in RFFs (P<0.05). Although the type of donor cells did not affect development to blastocyst, after transfer into recipients, RCC cloned embryos induced a higher initial pregnancy rate as compared to RFF cloned embryos (40 vs 20%). However, almost all pregnancies with either type of cloned embryos were lost by the middle of gestation and only one fully developed, live RCC-derived rabbit was obtained. Treatment of RFFs with NaBu significantly increased the level of acH3K9/14 and the proportion of nuclear transfer embryos developing to blastocyst (49 vs 33% with non-treated RFF, P<0.05). The distribution of acH3K9/14 in either group of cloned embryos did not resemble that in in vivo fertilized embryos suggesting that reprogramming of this epigenetic mark is aberrant in cloned rabbit embryos and cannot be corrected by treatment of donor cells with NaBu. Aggregation of embryos cloned from NaBu-treated RFFs with blastomeres from in vivo derived embryos improved development to blastocyst, but no cloned offspring were obtained. Two live cloned rabbits were produced from this donor cell type only after aggregation of cloned embryos with a parthenogenetic blastomere. Our study demonstrates that the levels of histone acetylation in donor cells and cloned embryos correlate with their developmental potential and may be a useful epigenetic mark to predict efficiency of SCNT in rabbits.     

Somatic cell nuclear transfer in the sheep induces placental defects that likely precede fetal demise

The efficiency of cloning by somatic cell nuclear transfer (SCNT) is poor in livestock with approximately 5% of transferred cloned embryos developing to term. SCNT is associated with gross placental structural abnormalities. We aimed to identify defects in placental histology and gene expression in failing ovine cloned pregnancies to better understand why so many clones generated by SCNT die in utero. Placentomes from SCNT pregnancies (n = 9) and age matched, naturally mated controls (n = 20) were collected at two gestational age ranges (105-134 days and 135-154 days; term = 147 days). There was no effect of cloning on total placental weight. However, cloning reduced the number of placentomes at both gestational ages (105-134 days: control 55.0 +/- 4.2, clone 44.7 +/- 8.0 and 135-154 days: control 72.2 +/- 5.1, clone 36.6 +/- 5.1; P < 0.001) and increased the mean individual placentome weight (105-134 days: control 10.6 +/- 1.3 g, clone 18.6 +/- 2.8 g and 135-154 days: control 6.6 +/- 0.6 g, clone 7.0 +/- 2.0 g; P < 0.02). Placentomes from cloned pregnancies had a significant volume of shed trophoblast and fetal villous hemorrhage, absent in controls, at both gestational age ranges (P < 0.001) that was shown to be apoptotic by activated caspase-3 immunoreactivity. Consequently, the volume of intact trophoblast was reduced and the arithmetic mean barrier thickness of trophoblast through which exchange occurs was altered (P < 0.001) at both gestational age ranges in clones. In addition, cloning reduced placental expression of key genes in placental differentiation and function. Thus, cloning by SCNT results in both gross and microscopic placental abnormalities. We speculate that trophoblast apoptosis, shedding, and hemorrhage may be causal in fetal death in ovine clones.     

Formation of nucleoli in interspecies nuclear transfer embryos derived from bovine, porcine, and rabbit oocytes and nuclear donor cells of various species

The most successful development of interspecies somatic cell nuclear transfer (iSCNT) embryos has been achieved in closely related species. The analyses of embryonic gene activity in iSCNT embryos of different species combinations have revealed the existence of significant aberrations in expression of housekeeping genes and genes dependent on the major embryonic genome activation (EGA). However, there are many studies with successful blastocyst (BL) development of iSCNT embryos derived from donor cells and oocytes of animal species with distant taxonomical relations (inter-family/inter-class) that should indicate proper EGA at least in terms of RNA polymerase I activation, nucleoli formation, and activation of genes engaged in morula and BL formation. We investigated the ability of bovine, porcine, and rabbit oocytes to activate embryonic nucleoli formation in the nuclei of somatic cells of different mammalian species. In iSCNT embryos, nucleoli precursor bodies originate from the oocyte, while most proteins engaged in the formation of mature nucleoli should be transcribed from genes de novo in the donor nucleus at the time of EGA. Thus, the success of nucleoli formation depends on species compatibility of many components of this complex process. We demonstrate that the time and cell stage of nucleoli formation are under the control of recipient ooplasm. Oocytes of the studied species possess different abilities to support nucleoli formation. Formation of nucleoli, which is a complex but small part of the whole process of EGA, is essential but not absolutely sufficient for the development of iSCNT embryos to the morula and BL stages.     

Overexpression of miR-101-2 in donor cells improves the early development of Holstein cow somatic cell nuclear transfer embryos

Accumulating studies have suggested that microRNA play a part in regulating multiple cellular processes, such as cell proliferation, apoptosis, the cell cycle, and embryo development. This study explored the effects of miR-101-2 on donor cell physiological status and the development of Holstein cow somatic cell nuclear transfer (SCNT) embryos in vitro. Holstein cow bovine fetal fibroblasts (BFF) overexpressing miR-101-2 were used as donor cells to perform SCNT; then, cleavage rate, blastocyst rate, inner cell mass-to-trophectoderm ratio, and the expression of some development- and apoptosis-related genes in different groups were analyzed. The miR-101-2 suppressed the expression of inhibitor of growth protein 3 (ING3) at mRNA and protein levels, expedited cell proliferation, and decreased apoptosis in BFF, suggesting that ING3, a target gene of miR-101-2, is a potential player in this process. Moreover, by utilizing donor cells overexpressing miR-101-2, the development of bovine SCNT embryos in vitro was significantly enhanced; the apoptotic rate in SCNT blastocysts was reduced, and the inner cell mass-to-trophectoderm ratio and SOX2, POU5F1, and BCL2L1 expression significantly increased, whereas BAX and ING3 expression decreased. Collectively, these findings suggest that miR-101-2 promotes BFF proliferation and vitality, reduces their apoptosis, and improves the early development of SCNT embryos.     

Epigenetic reprogramming in embryonic and foetal development upon somatic cell nuclear transfer cloning

The birth of 'Dolly', the first mammal cloned from an adult donor cell, has sparked a flurry of research activities to improve cloning technology and to understand the underlying mechanism of epigenetic reprogramming of the transferred somatic cell nucleus. Especially in ruminants, somatic cell nuclear transfer (SCNT) is frequently associated with pathological changes in the foetal and placental phenotype and has significant consequences for development both before and after birth. The most critical factor is epigenetic reprogramming of the transferred somatic cell nucleus from its differentiated status into the totipotent state of the early embryo. This involves an erasure of the gene expression program of the respective donor cell and the establishment of the well-orchestrated sequence of expression of an estimated number of 10 000-12 000 genes regulating embryonic and foetal development. The following article reviews the present knowledge on the epigenetic reprogramming of the transferred somatic cell nucleus, with emphasis on DNA methylation, imprinting, X-chromosome inactivation and telomere length restoration in bovine development. Additionally, we briefly discuss other approaches towards epigenetic nuclear reprogramming, including the fusion of somatic and embryonic stem cells and the overexpression of genes crucial in the formation and maintenance of the pluripotent status. Improvements in our understanding of this dramatic epigenetic reprogramming event will be instrumental in realising the great potential of SCNT for basic biological research and for various agricultural and biomedical applications.     

Morphological characterization of pre- and peri-implantation in vitro cultured, somatic cell nuclear transfer and in vivo derived ovine embryos

The processes of cellular differentiation were studied in somatic cell nuclear transfer (SCNT), in vitro cultured (IVC) and in vivo developed (in vivo) ovine embryos on days 7, 9, 11, 13, 17 and 19. SCNT embryos were constructed from in vitro matured oocytes and granulosa cells, and IVC embryos were produced by in vitro culture of in vivo fertilized zygotes. Most SCNT and IVC embryos were transferred to recipients on day 6 while some remained in culture for day 7 processing. In vivo embryos were collected as zygotes, transferred to intermediate recipients and retransferred to final recipients on day 6. All embryos were processed for examination by light and transmission electron microscopy or immunohistochemical labelling for alpha-1-fetoprotein and vimentin. Overall, morphological development of in vivo embryos was superior to IVC and SCNT embryos. Day 7 and particularly day 9 IVC and SCNT embryos had impaired hypoblast development, some lacking identifiable inner cell masses. On day 11, only in vivo and IVC embryos had developed an embryonic disc, and gastrulation was evident in half of in vivo embryos and one IVC embryo. By day 13, all in vivo embryos had completed gastrulation whereas IVC and SCNT embryos remained retarded. On days 17 and 19, in vivo embryos had significantly more somites and a more developed allantois than IVC and SCNT embryos. We conclude that IVC and particularly SCNT procedures cause a retardation of embryo development and cell differentiation at days 7-19 of gestation.     

Fluorescence resonance energy transfer analysis of mitochondrial:lipid association in the porcine oocyte

The role of endogenous lipid in the provision of energy during in vitro maturation of immature porcine oocytes has been studied. Fluorescence resonance energy transfer (FRET) acceptor bleaching methods have been used to examine mitochondrial:lipid droplet co-localisation in live oocytes. FRET experiments demonstrate whether organelles are within the FRET-distance (i.e. 6-10 nm), thus showing true association on a molecular scale. Immature and in vitro-matured porcine oocytes were stained with Mitotracker Green (MTG; mitochondria) and Nile Red (NR; lipid droplets). The data indicated sufficient overlap between MTG emission and NR excitation to support a FRET reaction and that mitochondria and lipid droplets were sufficiently co-localised for a FRET reaction to occur. When NR-stained lipid droplets were specifically bleached, a significant increase in the MTG signal in stained mitochondria was observed (FRET efficiency, E=22.2 +/- 3.18%). These results strongly suggest a metabolic role for lipid metabolism during oocyte maturation. This conclusion was reinforced by the use of inhibitors of fatty acid beta-oxidation, methyl palmoxirate or mercaptoacetate, exposure to which during oocyte maturation led to developmental failure post-fertilisation. These data provide strong evidence that MTG and NR can act as a FRET pair and that in porcine oocytes, mitochondria and lipid droplets lie within 6-10 nm of each other, indicating association on a molecular scale. The findings also suggest that endogenous triglycerides play an important role in energy metabolism during porcine in vitro maturation.     

Beneficial effects of a high fibre diet on oocyte maturity and embryo survival in gilts

The present study examined the effects of feeding gilts a high fibre diet from the third post-pubertal oestrus until either day 19 of the same cycle or insemination at the following oestrus on oocyte maturity, embryo survival and associated changes in reproductive hormone concentrations. Gilts fed with the high fibre diet had lower circulating oestradiol concentrations on days 17, 18 and 19 of the cycle and increased LH pulse frequency on day 18. More oocytes recovered on day 19 from gilts receiving the high fibre diet were at metaphase II after 46-h culture in medium containing 10% of their own follicular fluid, despite fewer large (>7 mm) follicles in these gilts when compared with control animals. There was no effect of diet on ovulation rate, corpora lutea size or progesterone concentrations on days 10-12 after insemination, but embryo survival on days 27-29 after insemination was higher in gilts that received the high fibre diet. This study demonstrates that a high fibre diet that increases embryo survival also improves oocyte maturity and provides information on endocrine correlates that may shed light on underlying mechanisms.     

Centrosome changes during meiosis in horse oocytes and first embryonic cell cycle organization following parthenogenesis, fertilization and nuclear transfer

Various types of cell cycle organization occur in mammals. In this study, centrosome changes during meiosis in horse oocytes, and first cell cycle organization following fertilization, parthenogenesis and nuclear transfer, were monitored. Cumulus oocyte complexes harvested from horse ovaries obtained from slaughtered mares were cultured in vitro. Meiotic oocytes of germinal vesicle (GV), germinal vesicle breakdown (GVBD), metaphase I and II (MI and MII) stages were selected at various set times during in vitro maturation. Embryos at the first cell cycle stage were generated by subjecting MII stage oocytes to fertilization by intracytoplasmic sperm injection (ICSI), parthenogenetic treatment or nuclear transfer. Centrosome changes during meiosis and the first cell cycle organization were detected by indirect immunofluorescent staining, using a mouse anti-alpha-tubulin antibody for microtubules and a rabbit anti-gamma-tubulin antibody for centrosomes. These examinations showed that the centrosomes of the horse oocyte reorganize themselves from the beginning of GV stage to leave only PCM of gamma-tubulin surrounding both poles of the MI and MII stage spindles. These MII oocytes can organize the separation of metaphase chromosomes during the first embryonic cell cycle by parthenogenetic treatment. When the MII oocytes were subjected to ICSI or nuclear transfer, one or two red-stained centrosomes of gamma-tubulin were introduced by the fertilising spermatozoon or the donor cell which associated with the sperm chromatin in the fertilized embryos and with the donor cell chromatin and microtubules in the cloned embryos. This finding suggests that centrosomes are not an essential component in the formation of the metaphase spindle during meiotic maturation of horse oocytes, but they can be introduced from the spermatozoon or donor cell and are necessary for the organization of normal embryonic development.     

Fate of centrosomes following somatic cell nuclear transfer (SCNT) in bovine oocytes

Cloning mammalians by somatic cell nuclear transfer (SCNT) remains inefficient. A majority of clones produced by SCNT fail to develop properly and of those which do survive, some exhibit early aging, premature death, tumors, and other pathologies associated with aneuploidy. Alterations of centrosomes are linked to aberrant cell cycle progression, aneuploidy, and tumorigenesis in many cell types. It remains to be determined how centrosomes are remodeled in cloned bovine embryos. We show that abnormalities in either distribution and/or number of centrosomes were evident in approximately 50% of reconstructed embryos following SCNT. Moreover, centrosome abnormalities and failed 'pronuclear' migration which manifested during the first cell cycle coincided with errors in spindle morphogenesis, chromosome alignment, and cytokinesis. By contrast, nuclear mitotic apparatus protein (NuMA) exhibited normal expression patterns at metaphase spindle poles and in 'pronucleus' during interphase. The defects in centrosome remodeling and 'pronuclear' migration could lead to chromosome instability and developmental failures associated with embryo production by SCNT. Addressing these fundamental problems may enhance production of normal clones.     

转移印花增稠剂的流变性与微观形貌

以转移印花纸涂层改性用增稠剂高取代羟丙基纤维素（H-HPC）和羧甲基纤维素钠（CMC）为研究对象,采用稳态剪切和频率扫描相结合的方法研究了H-HPC、CMC溶液的流变性及其共混溶液在不同环境中的相容性,并利用光学和原子力显微镜对H-HPC、CMC和糊料膜的微观形貌进行观测。研究表明：CMC的结构粘度高于H-HPC并体现出更明显的假塑性和触变性;随着H-HPC或CMC含量的增加,溶液的弹性增强且粘性减弱;酸性、弱碱性以及尿素对H-HPC/CMC溶液的表观粘度和黏弹性影响不大;在80 ℃以上干燥时,可获得H-HPC和CMC共混均匀且表面平整的糊料膜。     

Estrous synchronization and establishment of pregnancy in bovine embryo transfer recipients

Characteristics of donors, embryos, recipients, and transfer procedures were examined for relationships with establishment of pregnancy. Data were from records of 1202 embryos transferred by the professional staff of a large embryo transfer company. Average pregnancy rate was 74.6%. Variables affecting establishment of pregnancy were service sire, embryo quality, stage of estrous cycle in recipient, quadratic effect of synchrony, and transfer quality. Because the direct or indirect effect of sire must be established at conception, these data demonstrate a latent effect of sire on pregnancy. One would expect the highest pregnancy rate among excellent quality embryos transferred with no delays or complications into recipients that had displayed estrus at the same time or prior to the donor yet were relatively early in their estrous cycles. There also was a tendency for pregnancy rate to decrease with advancing maturity of the embryo.     

Effect of the time interval between fusion and activation on nuclear state and development in vitro and in vivo of bovine somatic cell nuclear transfer embryos

This study indicated that prolonged exposure of donor cell nuclei to oocyte cytoplasm before activation results in abnormal chromatin morphology, and reduced development to compacted morula/blastocyst stage in vitro. However, after transfer of embryos to recipients, there was no difference in pregnancy rates throughout gestation. Chromatin morphology was evaluated for embryos held 2, 3, 4 and 5 h between fusion and activation. In embryos held 2 h, 15/17 (88.2%) embryos contained condensed chromosomes, while only 12/24 (50.0%) embryos held 3 h exhibited this characteristic. The proportion of embryos with elongated or fragmented chromosomes tended to increase with increased hold time. While 15/19 (78.9%) of embryos held 2 h developed a single pronucleus 6 h after activation, only 8/22 (36.4%) had one pronucleus after a 4-h hold. Embryos held 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 h cleaved at rates of 207/281 (73.7%), 142/166 (85.5%), 655/912 (71.8%), 212/368 (57.6%), 406/667 (60.9%), 362/644 (56.2%) and 120/228 (52.6%) respectively. Further development to compacted morula/blastocyst stage occurred at rates of 78/281 (27.8%), 42/166 (25.3%), 264/912 (28.9%), 79/368 (21.5%), 99/667 (14.8%), 94/644 (14.6%) and 27/228 (11.8%) respectively. Embryos held less than 2.5 h between fusion and activation established pregnancies in 18/66 (27.3%) of recipients, while embryos held over 2.5 h established pregnancies at a rate of 17/57 (29.8%). This study indicates that holding bovine nuclear transfer embryos less than 2.5 h between fusion and activation results in improved nuclear morphology and increased development to compacted morula/blastocyst stage, and results in pregnancy rates equivalent to embryos held over 2.5 h.     

Anti-inflammatory and anti-oxidative effect of curcumin in connective tissue type mast cell

Curcumin in turmeric from rhizome of plant Curcuma longa was investigated on its anti-inflammatory effect with canine cutaneous mastocytoma mast cells. Though the degranulation induced by neuropeptide substance P, specific mast cell secregtagogue Compound 48/80 and immunoglobulin IgG were reached above 10%, curcumin reduced the release below 4.6% at 10 μM without cytotoxicity. Inhibitory effect of curcumin on [Ca²⁺]_i elevation was also confirmed. ROS induced by Compound 48/80 were evaluated with dichlorodihydrofluorescein diacetate (DCFH-DA), and were lowered by curcumin in dose dependent manner. Cell membrane lipid peroxidation was monitored with diphenyl-1-pyrenylphosphine (DPPP). Curcumin decreased cell membrane lipid peroxidation induced by arachidonic acid in the concentration above 0.01 μM. Curcumin also inhibited the protein tyrosine- and threonine-phosphorylations around 33 and 45 kDa, respectively. Taking these findings into consideration with the inhibitory effects on connective tissue type mast cell, there is a potential use to ameliorate inflammation-related chronic diseases.     

Developmental disparity between in vitro-produced and somatic cell nuclear transfer bovine days 14 and 21 embryos: implications for embryonic loss

In ruminants, the greatest period of embryonic loss coincides with the period of elongation when the embryonic disc is formed and gastrulation occurs prior to implantation. The impact of early embryonic mortality is not only a major obstacle to the cattle breeding industry but also impedes the application of new reproductive technologies such as somatic cell nuclear transfer (SCNT). In the present study, days 14 and 21 bovine embryos, generated by either in vitro-production (IVP) or SCNT, performed by either subzonal injection (SUZI) or handmade cloning (HMC), were compared by stereomicroscopy, immunohistochemistry, and transmission electron microscopy to establish in vivo developmental milestones. Following morphological examination, samples were characterized for the presence of epiblast (POU5F1), mesoderm (VIM), and neuroectoderm (TUBB3). On D14, only 25, 15, and 7% of IVP, SUZI, and HMC embryos were recovered from the embryos transferred respectively, and similar low recovery rates were noted on D21, suggesting that most of the embryonic loss had already occurred by D14. A number of D14 IVP, SUZI, and HMC embryos lacked an epiblast, but presented trophectoderm and hypoblast. When the epiblast was present, POU5F1 staining was limited to this compartment in all types of embryos. At the ultrastructural level, SCNT embryos displayed abundant secondary lysosomes and vacuoles, had fewer mitochondria, polyribosomes, tight junctions, desmosomes, and tonofilaments than their IVP counterparts. The staining of VIM and TUBB3 was less distinct in SCNT embryos when compared with IVP embryos, indicating slower or compromised development. In conclusion, SCNT and to some degree, IVP embryos displayed a high rate of embryonic mortality before D14 and surviving embryos displayed reduced quality with respect to ultrastructural features and differentiation markers.     

Evaluation of genetic components in traits related to superovulation,in vitro fertilization,and embryo transfer in Holstein cattle

The objectives of this study were to estimate variance components and identify regions of the genome associated with traits related to embryo transfer in Holsteins. Reproductive technologies are used in the dairy industry to increase the reproductive rate of superior females. A drawback of these methods remains the variability of animal responses to the procedures. If some variability can be explained genetically, selection can be used to improve animal response. Data collected from a Holstein dairy farm in Florida from 2008 to 2015 included 926 superovulation records (number of structures recovered and number of good embryos), 628 in vitro fertilization records (number of oocytes collected, number of cleaved embryos, number of high- and low-quality embryos, and number of transferrable embryos), and 12,089 embryo transfer records (pregnancy success). Two methods of transformation (logarithmic and Anscombe) were applied to count variables and results were compared. Univariate animal models were fitted for each trait with the exception of pregnancy success after embryo transfer. Due to the binary nature of the latter trait, a threshold liability model was fitted that accounted for the genetic effect of both the recipient and the embryo. Both transformation methods produced similar results. Single-step genomic BLUP analyses were performed and SNP effects estimated for traits with a significant genetic component. Heritability of number of structures recovered and number of good embryos when log-transformed were 0.27 ± 0.08 and 0.15 ± 0.07, respectively. Heritability estimates from the in vitro fertilization data ranged from 0.01 ± 0.08 to 0.21 ± 0.15, but were not significantly different from zero. Recipient and embryo heritability (standard deviation) of pregnancy success after embryo transfer was 0.03 (0.01) and 0.02 (0.01), respectively. The 10-SNP window explaining the largest proportion of variance (0.37%) for total structures collected was located on chromosome 8 beginning at 55,663,248 bp. Similar regions were identified for number of good embryos, with the largest proportion of variance (0.43%) explained by a 10-SNP window on chromosome 14 beginning at 26,713,734 bp. Results indicate that there is a genetic component for some traits related to superovulation and that selection should be possible. Moreover, the genetic component for superovulation traits involves some genomic regions that are similar to those for other fertility traits currently evaluated.