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In vitro embryo production (IVP) in cattle has gained worldwide interest in recent years, but the efficiency of using IVP embryos for calf production is far from optimal. This review will examine the pregnancy retention rates of IVP embryos and explore causes for pregnancy failures. Based on work completed over the past 25 yr, only 27% of cattle receiving IVP embryos will produce a live calf. Approximately 60% of these pregnancies fail during the first 6 wk of gestation. When compared with embryos generated by superovulation, pregnancy rates are 10% to 40% lower for cattle carrying IVP embryos, exemplifying that IVP embryos are consistently less competent than in vivo-generated embryos. Several abnormalities have been observed in the morphology of IVP conceptuses. After transfer, IVP embryos are less likely to undergo conceptus elongation, have reduced embryonic disk diameter, and have compromised yolk sac development. Marginal binucleate cell development, cotyledon development, and placental vascularization have also been documented, and these abnormalities are associated with altered fetal growth trajectories. Additionally, in vitro culture conditions increase the risk of large offspring syndrome. Further work is needed to decipher how the embryo culture environment alters post-transfer embryo development and survival. The risk of these neonatal disorders has been reduced by the use of serum-free synthetic oviductal fluid media formations and culture in low oxygen tension. However, alterations are still evident in IVP oocyte and embryo transcript abundances, timing of embryonic cleavage events and blastulation, incidence of aneuploidy, and embryonic methylation status. The inclusion of oviductal and uterine-derived embryokines in culture media is being examined as one way to improve the competency of IVP embryos. To conclude, the evidence presented herein clearly shows that bovine IVP systems still must be refined to make it an economical technology in cattle production systems. However, the current shortcomings do not negate its current value for certain embryo production needs and for investigating early embryonic development in cattle. [ABSTRACT FROM AUTHOR]

Our objectives were to determine the effects of the administration of recombinant bovine somatotropin (bST) at the initiation of a fixed-time AI (TAI) protocol on concentrations of plasma IGF-1, follicle diameter, embryo/fetal size, and pregnancy rates in replacement beef heifers. Four hundred and fourteen Angus-based beef heifers were enrolled in a completely randomized design at 4 locations from January to July of 2016. All heifers were exposed to the 7-d CO-Synch + controlled internal drug release (CIDR) protocol where they received a 100-µg injection of GnRH and a CIDR insert on day -9, 25 mg of PGF2a at CIDR removal on day -2, followed by a 100-µg injection of GnRH and TAI 54 ± 2 h later on day 0. Within location, all heifers were randomly assigned to 1 of 2 treatments: 1) heifers that received 650 mg of bST on day -9 (BST; n = 191); or 2) heifers that did not receive bST on day -9 (CONTROL; n = 223). Blood samples were collected on day -9, 0, 28, and 60 to determine the plasma concentrations of IGF-1. Follicle diameter was determined on day -2 and 0 by transrectal ultrasonography. Pregnancy was diagnosed via transrectal ultrasonography on day 28 or 35, and again at least 30 d after the end of the breeding season. Embryo morphometry was assessed by measuring crown-to-rump length (CRL) on day 28, and fetal size was assessed by measuring crown-to-nose-length (CNL) on day 60. Concentrations of plasma IGF-1 did not differ between treatments on day -9 (P = 0.924), 28 (P = 0.075), and 60 (P = 0.792); however, concentrations of plasma IGF-1 were greater (P < 0.001) in BST-treated heifers at TAI (372.4 ± 16.6 vs. 193.7 ± 16.6 ng/ml). No differences (P = 0.191) were detected for follicle diameter between CONTROL and BST treatments on day -2 or 0. Pregnancy rates to TAI (PR/AI) were greater (P = 0.028) for CONTROL compared to BST heifers (42.5 ± 4.0 vs. 29.9 ± 4.1%). No differences (P = 0.536) in CRL were observed on day 28 between CONTROL and BST heifers. In addition, no difference (P = 0.890) was observed for CNL between CONTROL and BST treatments. Final pregnancy rates did not differ (P = 0.699) between treatments. The administration of bST to beef heifers at the initiation of a TAI protocol increased plasma concentrations of IGF-1 at TAI; however, failed to enhance follicle diameter, embryo/fetal size, and reduced PR/AI. [ABSTRACT FROM AUTHOR]

The mixing of mitochondrial DNA (mtDNA) from the donor cell and the recipient oocyte in embryos and offspring derived from somatic cell nuclear transfer (SCNT) compromises genetic integrity and affects embryo development. We set out to generate SCNT embryos that inherited their mtDNA from the recipient oocyte only, as is the case following natural conception. While SCNT blastocysts produced from Holstein (Bos taurus) fibroblasts depleted of their mtDNA, and oocytes derived from Angus (Bos taurus) cattle possessed oocyte mtDNA only, the coexistence of donor cell and oocyte mtDNA resulted in blastocysts derived from nondepleted cells. Moreover, the use of the reprogramming agent, Trichostatin A (TSA), further improved the development of embryos derived from depleted cells. RNA-seq analysis highlighted 35 differentially expressed genes from the comparison between blastocysts generated from nondepleted cells and blastocysts from depleted cells, both in the presence of TSA. The only differences between these two sets of embryos were the presence of donor cell mtDNA, and a significantly higher mtDNA copy number for embryos derived from nondepleted cells. Furthermore, the use of TSA on embryos derived from depleted cells positively modulated the expression of CLDN8, TMEM38A, and FREM1, which affect embryonic development. In conclusion, SCNT embryos produced by mtDNA depleted donor cells have the same potential to develop to the blastocyst stage without the presumed damaging effect resulting from the mixture of donor and recipient mtDNA. [ABSTRACT FROM AUTHOR]

Epigenetic reprogramming is necessary in somatic cell nuclear transfer (SCNT) embryos in order to erase the differentiation-associated epigenetic marks of donor cells. However, such epigenetic memories often persist throughout the course of clonal development, thus decreasing cloning efficiency. Here, we explored reprogramming-refractory regions in bovine SCNT blastocyst transcriptomes. We observed that histone genes residing in the 1.5 Mb spanning the cow HIST1 cluster were coordinately downregulated in SCNT blastocysts. In contrast, both the nonhistone genes of this cluster, and histone genes elsewhere remained unaffected. This indicated that the downregulation was specific to HIST1 histone genes. We found that, after trichostatin A treatment, HIST1 histone genes were derepressed, and DNA methylation at their promoters was decreased to the level of in vitro fertilization embryos. Therefore, our results indicate that the reduced expression of HIST1 histone genes is a consequence of poor epigenetic reprogramming in SCNT blastocysts [ABSTRACT FROM AUTHOR]

Development of the mammalian pre-implantation embryo is susceptible to disruption by elevated temperature. The molecular and biochemical bases for developmental, genetic, and other differences in embryonic resistance to heat shock are largely not known. Here we tested the hypothesis that increasing free cholesterol content could improve embryonic resistance to heat shock. Culture of bovine embryos at 41.0°C for 15 h beginning at 30 h after insemination (1-to 2-cell stage) reduced development to the blastocyst stage. Reduction in embryonic cholesterol content by culture with methyl-P-cyclodextrin (MBCD) reduced development. This effect of MBCD could be abrogated in 1 of 2 experiments if the molecule was loaded with cholesterol before addition to culture medium. Even though culture with cholesterol-loaded MBCD increased free cholesterol content, it did not increase resistance of embryos to heat shock. Treatment of embryos with cholesterol-loaded high density lipoprotein (HDL) increased embryonic resistance to heat shock even though it slightly reduced embryo cholesterol content. It is likely that other actions of HDL (e.g., protection from free radicals) were responsible for the thermoprotective properties of this molecule. A final experiment was performed to determine whether the increased resistance of embryos at d 5 of development to heat shock as compared with the 2-cell embryo was due to changes in free cholesterol content. However, there was no significant difference in cholesterol content between 2-cell embryos and d 5 embryos that were > 16 cells in development. In conclusion, raising cholesterol content does not improve embryonic survival in response to heat shock. Depletion of cholesterol, in contrast, reduces competence of embryos to develop to the blastocyst stage. High density lipoprotein is thermoprotective to embryos and probably acts through a mechanism independent of its actions on embryonic content of free cholesterol. [ABSTRACT FROM AUTHOR]

BACKGROUND: Early embryo development (EED) forms the basis of assisted reproductive technologies (ARTs), which are used to treat human infertility and to propagate other mammalian species. Thyroid hormones (THs) play an important role in the post-implantation development of the embryo in mammals; however, the effects of THs on pre-attachment embryos are not known. Currently utilized in-vitro embryo production media are devoid of THs and hence our main objective was to examine whether THs affected EED in a bovine model. [ABSTRACT FROM PUBLISHER]

Presents abstracts of studies about animal science presented at the March 2001 conference of the American Society of Animal Science Midwestern Section. `Identification of Genes Downstream of Myostatin in the Developing Bovine Embryo,' by T.P.L. Smith et al.; `Protein Accretion in Pigs Infected With Mycoplasma hyopneumoniae,' by J. Escobar et al.; `Implications of Feedback Regulation of Beta-adrenergic Signaling,' by S.E. Mills.

Presents information on a study which concluded that reducing oxygen tension below atmospheric levels was beneficial for culturing bovine zygotes. Effects of metal chelation; Methodology of the study; Results and discussion.

Examines the effects of free radicals and hypotaurine on the development of bovine embryos produced by in vitro fertilization of in vitro-matured oocytes. Effects of oxygen concentration on development of 4- to 6-cell embryos; Scavenging effects of hypotaurine and superoxide dismutase on free radicals.

Determines the effects of culture systems and renewal of medium during in vitro development of in-vitro produced bovine embryos. Reduced development of embryos to hatched blastocyst in both the well and microdrip systems; Detrimental effects of ammonium concentration on IVM.

The article looks at a study which evaluate the relationship of these same factors to fertilization status of the ovum and embryo quality as well as to determine further the relationship of accessory sperm number to fertilization status and embryo quality. It mentions accessory sperm number and its relationship to fertilization and embryo quality was evaluated in cattle after nonsurgical recovery of ova or embryos of artificially inseminated cattle.

Presents an abstract of the research titled `Systemic vs Local Embryotoxic Effect of Early Luteal Regression in Cattle,' by H.J. Hernandez-Fonseca, B.L. Sayre, et al. Removal of the regressing corpus luteum to achieve normal embryonic survival in the animals.

Presents an abstract of the research titled `The Effects of Antibiotics on Bovine Embryo Development in vitro,' by S. Wang, G.R. Holyoak, et al. Utilization of a randomized complete block design with 3 treatments.

Presents an abstract of the research titled `The Effect of 24 Hour Shipping on Fresh Transgenic Bovine Embryos,' by N. Putnam, W. Plummer, et al. Inefficiency of the transport of fresh embryos via thermos and ground service.

Presents an abstract of the research titled `Effect of Taurine on Development of in vitro Produced Bovine Embryos,' by J.N. Caamano and C.R. Youngs. Focus on the effect of taurine on bovine embryo development in a cell-free and serum-free culture system.

Presents an abstract of the research titled `Micro-Labeling of Bovine Embryos: Polysilicon Micro-Chip Biocompatability,' by K.D. Easley, A.R. Williams, et al. Focus on the production of bovine embryos through follicular oocyte aspiration.