Pregnancies, calves and calf viability after transfer of in vitro produced bovine embryos

Could assisted reproductive techniques affect equine fetal membranes and neonatal outcome?

Embryo transfer (ET) and intracytoplasmic sperm injection (ICSI) are widely used in equine species, but their effects on fetal adnexa and neonates have not been investigated yet. The aim of this study was to retrospectively evaluate whether pregnancies obtained by ET or ICSI could be associated with the presence of macroscopic alterations of fetal membranes (FM) and umbilical cord (UC) and if the use of these techniques could influence neonatal outcome. Sixty-six light breed mares hospitalized at the Veterinary Teaching Hospital, University of Bologna, for attending delivery were included in the study. Mares were divided into Artificial Insemination (AI; 32/66 mares, 48 %), Embryo Transfer (ET; 12/66 mares, 18.2 %) and Intracytoplasmic Sperm Injection (ICSI; 22/66 mares, 33 %) groups. All the medical reports of mares and their foals were reviewed and data about mare, pregnancy, foaling, fetal membranes, umbilical cord and foal were recorded. The occurrence of dystocia resulted statistically different between AI group and ICSI group (p = 0.0066), and between AI group and ET group (p = 0.044). Macroscopic examination of FM revealed alterations in 30/66 mares (46 %): 8/32 in AI (25 %), 7/12 in ET (58 %) and 15/22 in ICSI (68 %) with significant lower incidence in AI compared to ET (p = 0.04) and ICSI (p = 0.002) groups. Alterations reported were chorionic villi hypoplasia, chorioallantois edema, allantois cysts, necrotic areas and greenish-grey concretions. Total length of UC resulted significantly shorter in ICSI group (49 ± 9 cm; p < 0.03) compared to AI (60 ± 17 cm) and ET (59 ± 15 cm). However, there were no differences in the incidence of foals' diseases at birth and in foals' survival among groups (p > 0.05). The results demonstrate that transfer of in vivo or in vitro produced embryos may lead to alterations of placental development, as observed in other species, without being associated with a higher incidence of neonatal morbidity and mortality. Further studies about trophoblast development, FM histological evaluation, and placental gene expression should be carried out to clarify the mechanisms underlying the placental alterations.

Review: Large offspring syndrome in ruminants: current status and prediction during pregnancy

Large/abnormal Offspring Syndrome (LOS/AOS) is a congenital overgrowth condition of cattle and sheep, characterized by macrosomia, abdominal wall defects, organomegaly, difficulty to stand and suckle at parturition. The condition was first described as an exclusive consequence of assisted reproductive technologies, such as in vitro production and somatic cell nuclear transfer (cloning). However, we recently reported the spontaneous occurrence of this syndrome in cattle. The etiology of LOS is unclear, although the syndrome is an epigenetic condition characterized by multi-locus loss-of-imprinting, global dysregulation of small and long RNAs, changes in DNA methylation, and altered chromosomal architecture. These molecular and epigenetic changes affect biological pathways implicated in organ size, cell proliferation, cell survival, resulting in the phenotypes which characterize LOS. The lack of accurate tools for the prediction and diagnosis of LOS and the prevention of dystocia resulting from fetal overgrowth is a major concern for the dairy and beef industries. Furthermore, death of the calf and/or dam during calving adds animal welfare issues and affects the net income of the industry. An early diagnosis of LOS/AOS during gestation is critical to facilitate the decision-making process on whether to allow the pregnancy to continue or not in order to prevent harm to the dam as well as to provide producers with the timely necessary information to prepare for a difficult birth. The present review summarizes the definition, traits, incidence, and molecular characteristics of LOS to provide information and serve as a guide for future investigations regarding the early identification of LOS during pregnancy in cattle.

Practical application of an impractical bovine genotype: creating bilateral twin pregnancies in Trio allele carriers

Bovine twin birth is associated with detriments, including increased embryo/fetal losses, malpresentation, and dystocia. Incidence of these is lessened in bilateral compared with unilateral twin pregnancy. This study was undertaken to assess the use of follicular ablation by aspiration to create bilateral twin pregnancies in females with genetic potential for ~3.5 ovulations per cycle (Trio allele carriers). In experiment 1, carriers (n = 30) and noncarriers (n = 10) were synchronized for ovulation and timed artificial insemination (TAI). Follicles (>5 mm) in excess of one per ovary were aspirated ~16 h preceding TAI. Follicle count for females with follicles on only one ovary was reduced to two. Blood was sampled 2 wk post-TAI to assess progesterone (P4) concentrations; embryo count was determined by ultrasound 6 wk post-TAI. Circulating P4 concentration post-TAI was significantly (P < 0.001) associated with both genotype and subsequent pregnancy status (pregnant noncarriers: 7.06 ± 0.68 ng/mL; pregnant carriers: 5.54 ± 0.55 ng/mL; nonpregnant noncarriers: 5.22 ± 1.05 ng/mL; nonpregnant carriers: 3.13 ± 0.42 ng/mL). Experiment 2 was undertaken to offset the negative effects of follicular aspiration on subsequent P4 concentration observed in experiment 1. Carriers (n = 38) and noncarriers (n = 32) were submitted to TAI and follicle ablation as described for experiment 1. Additionally, accessory corpora lutea (CL) were induced in carriers by the administration of human chorionic gonadotropin (carriers) at day 6 post-TAI. Consequently, P4 concentration post-TAI was significantly (P < 0.05) associated with subsequent pregnancy status (pregnant: 8.48 ± 0.61 ng/mL; nonpregnant: 6.70 ± 0.63 ng/mL) but not with genotype (carrier: 8.01 ± 0.59 ng/mL; noncarrier: 7.17 ± 0.64 ng/mL). Embryo number was greater in carriers (exp. 1: 1.64 ± 0.81; exp 2: 1.45 ± 0.09) vs. noncarriers (1.00 ± 0.00, both experiments). Single, twin, and triplet pregnancies occurred in carriers in experiment 1, whereas multiples in experiment 2 were limited to twin pregnancies. Genotype effects on pregnancy rate were not significant (P > 0.10) in either experiment. Results suggest that follicular ablation to create bilateral twin pregnancies in Trio carriers is feasible but requires the induction of accessory CL to offset the negative effects of follicular aspiration on subsequent P4 concentration and associated fertility outcomes.

Reproductive Outcomes and Endocrine Profile in Artificially Inseminated versus Embryo Transferred Cows

Simple Summary

Bovine embryos are nowadays produced in laboratories, frozen and transferred to other cows. However, the percentage of pregnancies obtained after these transfers as well as difficulties found during labor, especially due to increased size of calves, are a matter of great concern. One of the possible explanations for these problems relies on the embryo being produced in in vitro conditions (laboratory settings), more specifically the culture medium (liquid) used to develop these embryos. In an attempt to better mimic what happens naturally, female reproductive liquids (from oviducts and uterus) were used as a supplement to the culture of the embryos. As controls, embryos produced using the standard protocol in the laboratory were produced, as well as embryos derived from artificial insemination of cows (in vivo). An evaluation on the pregnancy rates, how the hormonal profile of the recipients changed during pregnancy, difficulties during parturitions, and phenotype of calves were recorded. Results showed that all the groups were very similar, but many differences were noted on the hormonal profiles during pregnancy. In conclusion, all systems provided safe production of calves, but long-term analysis of these calves is necessary to understand the future impact of the laboratory protocols.

Abstract

The increasing use of in vitro embryo production (IVP) followed by embryo transfer (ET), alongside with cryopreservation of embryos, has risen concerns regarding the possible altered pregnancy rates, calving or even neonatal mortality. One of the hypotheses for these alterations is the current culture conditions of the IVP. In an attempt to better mimic the physiological milieu, embryos were produced with female reproductive fluids (RF) as supplements to culture medium, and another group of embryos were supplemented with bovine serum albumin (BSA) as in vitro control. Embryos were cryopreserved and transferred while, in parallel, an in vivo control (artificial insemination, AI) with the same bull used for IVP was included. An overview on pregnancy rates, recipients’ hormonal levels, parturition, and resulting calves were recorded. Results show much similarity between groups in terms of pregnancy rates, gestation length and calves’ weight. Nonetheless, several differences on hormonal levels were noted between recipients carrying AI embryos especially when compared to BSA. Some calving issues and neonatal mortality were observed in both IVP groups. In conclusion, most of the parameters studied were similar between both types of IVP derived embryos and the in vivo-derived embryos, suggesting that the IVP technology used was efficient enough for the safe production of calves.

Recent progress in bovine in vitro-derived embryo cryotolerance: Impact of in vitro culture systems, advances in cryopreservation and future considerations

Cryopreservation of in vitro-derived bovine embryos is a crucial step for the widespread reproduction and conservation of valuable high-merit animals. Given the current popularity of bovine in vitro embryo production (IVP), there is a demand for a highly efficient ultra-low temperature storage method in order to maximize donor ovum pickup (OPU) turn-over, recipient availability/utilization and domestic/overseas commercial trading opportunities. However, IVP bovine embryos are still very sensitive to chilling and cryopreservation, and despite recent progress, a convenient (simple and robust) protocol has not yet been developed. At the moment, there are two methods for bovine IVP embryo cryopreservation: slow programmable freezing and vitrification. Both of the aforementioned techniques have pros and cons. While controlled-rate slow cooling can easily be adapted for direct transfer (DT), ice crystal formation remains an issue. On the other hand, vitrification solved this problem but the possibility of successful DT commercial incorporation remains to be determined. Moreover, simplification of the vitrification protocol (including warming) through the use of an in-straw dilution without the use of a microscope is a prerequisite for its use under farm conditions. This review summarizes the bovine IVP embryo cryopreservation achievements, strengths and limitations of both freezing systems and prospective improvements to enhance cryosurvival, as well as perspectives on future directions of this assisted reproductive technology.

The presence of synthetic polymers in the maturation medium affects the cryotolerance and developmental capacity after parthenogenic activation of vitrified goat oocytes

The purpose of this present study is to assess if addition of the synthetic polymers in maturation medium can influence cryotolerance and subsequently embryonic development of mammalian oocytes. We examined the roles of two polymers, including polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP), on in vitro maturation (IVM), embryonic developmental capacity, and cryotolerance of goat oocytes. The present study includes two parts. At first, goat cumulus-oocyte complexes (COCs) were matured in a medium supplemented with 10% fetal bovine serum (FBS), 3 mg/ml PVP, or 1 mg/ml PVA, respectively. Data of oocyte with first polar body, cleavage, and blastocyst following parthenogenetic activation (PA) were recorded. Secondly, after maturation in the above medium, oocytes were vitrified using the Cryotop technique and then the morphology, cleavage and blastocyst formation of vitrified oocytes have been checked. The results demonstrated that the adding of PVP or PVA in maturation medium can't affect IVM of goat oocytes in comparison with FBS, as concern cumulus cell expansion, first polar body formation, and embryonic development. Additionally, without plunging into liquid nitrogen, only exposure to the vitrification and warming solutions cannot also influence the quality of oocytes, in terms of morphology, cleavage, and blastocyst formation. However, after IVM with synthetic polymers and vitrification, the ratio of oocytes with standard morphology in PVP or PVA group was only 59.47% ± 3.56% or 54.86% ± 5.19%, respectively, and was significantly less than that in the FBS group (89.37% ± 4.52%, P < 0.05). Furthermore, the cleavage ratio of oocytes in PVP or PVA group was 37.41% ± 4.17% or 27.71% ± 3.91% and was considerably less than that in the FBS group (64.97% ± 4.69%, P < 0.05). In addition, the cleavage ratio in PVP group was statistically higher than that in PVA group (P < 0.05). In terms of blastocyst development, a significant difference was observed between the synthetic polymer group and the FBS group (24.96% ± 3.62%, P < 0.05). However, the blastocyst ratio in the PVA group (7.51% ± 1.68%) was statistically less than the PVP groups (13.20% ± 4.59%, P < 0.05) and the FBS group (P < 0.05). In conclusion, two potential serum replacements, either PVP or PVA, can support IVM and embryonic development of goat oocytes at the concentration used in this study. But IVM with synthetic polymers supplemented to maturation medium may reduce the cryotolerance of oocytes. Additionally, the supportive function of PVP on embryonic development of vitrified oocytes might be better than that of PVA.

Efficient one-step direct transfer to recipients of thawed bovine embryos cultured in vitro and frozen in chemically defined medium

Direct transfer (DT) of cryopreserved embryos to recipients facilitates on-farm application. We analyzed a new freezing/thawing (F/T) procedure for in vitro produced (IVP) embryos, integrating: 1) an ethylene-glycol based system; 2) a culture step without protein; and 3) a synthetic protein substitute (CRYO3) in cryopreservation medium. IVP embryos from abattoir ovaries were cultured in groups in BSA-containing synthetic oviduct fluid with or without 0.1% fetal calf serum (FCS) until Day-6. Morulae and early blastocysts were subsequently cultured without protein from Day-6 onwards. Day 7 and Day 8 expanded blastocysts (EXB) were subjected to F/T or vitrification/warming (V/W). Thawed and warmed EXB were cultured in vitro, and development rates, cell counts and dead cells were analyzed in surviving embryos. V/W improved survival over F/T (live and hatching rates at 2 h, 24 h and 48 h) (P < 0.0001), and FCS before Day 6 did not affect in vitro survival. After F/T, embryos had lower cell counts in the ICM, TE and total cells than after V/W. Day-7 embryos after F/T showed % apoptotic, % pycnotic and % total dead cells higher (p < 0.05) than their Day-8 counterparts, probably because F/T reduced the numbers of ICM cells within Day-8 embryos. Thereafter, Day-7 blastocysts were transferred to heifers in an experimental herd. There were no differences in birth rates with frozen (-FCS [n = 40]: 45%; +FCS [n = 14]: 28%), vitrified (-FCS [n = 47]: 53%; +FCS [n = 11]: 36%) and fresh (-FCS [n = 30]: 47%; +FCS [n = 17]: 53%) embryos. However, frozen embryos produced with FCS showed 5/9 miscarriages after Day-40. Calves born from frozen (n = 22), vitrified (n = 29) and fresh (n = 22) transfers did not differ in birth weight, gestation length and daily gain weight (P > 0.10). Subsequently, transfer of frozen embryos (n = 29) derived from oocytes collected from live, hormonally stimulated cows in experimental herd, led to pregnancy rates of 57% (heifers) and 40% (dry cows). with EXB on Day-62 Finally, embryos produced with BSA were transferred to cows in an on-field trial (frozen [n = 80]; fresh [n = 58]), with no differences in pregnancy rates (days 30-40). Pregnancy and birth rates could not be predicted from in vitro approaches. The new F/T system yields pregnancy and birth rates comparable to vitrified and fresh embryos without birth overweight. The absence of products of animal origin, defined chemical composition, and direct transfer entail sanitary, manufacturing and application advantages.

Overgrowth Syndrome

Large offspring syndrome (LOS) is a fetal overgrowth condition in bovines most often observed in offspring conceived with the use of assisted reproductive technologies (ART). Phenotypes observed in LOS include, overgrowth, enlarged tongues, umbilical hernias, muscle and skeleton malformations, abnormal organ growth and placental development. Although LOS cases have only been reported to be associated with ART, fetal overgrowth can occur spontaneously in cattle (S-LOS). S-LOS refers to oversized calves that are born at normal gestation lengths. ART-induced LOS has been characterized as an epigenetic syndrome, more specifically, a loss-of-imprinting condition. We propose that S-LOS is also a loss-of-imprinting condition.

Mechanisms of epigenetic remodelling during preimplantation development

Epigenetics involves mechanisms independent of modifications in the DNA sequence that result in changes in gene expression and are maintained through cell divisions. Because all cells in the organism contain the same genetic blueprint, epigenetics allows for cells to assume different phenotypes and maintain them upon cell replication. As such, during the life cycle, there are moments in which the epigenetic information needs to be reset for the initiation of a new organism. In mammals, the resetting of epigenetic marks occurs at two different moments, which both happen to be during gestation, and include primordial germ cells (PGCs) and early preimplantation embryos. Because epigenetic information is reversible and sensitive to environmental changes, it is probably no coincidence that both these extensive periods of epigenetic remodelling happen in the female reproductive tract, under a finely controlled maternal environment. It is becoming evident that perturbations during the extensive epigenetic remodelling in PGCs and embryos can lead to permanent and inheritable changes to the epigenome that can result in long-term changes to the offspring derived from them, as indicated by the Developmental Origins of Health and Disease (DOHaD) hypothesis and recent demonstration of inter- and trans-generational epigenetic alterations. In this context, an understanding of the mechanisms of epigenetic remodelling during early embryo development is important to assess the potential for gametic epigenetic mutations to contribute to the offspring and for new epimutations to be established during embryo manipulations that could affect a large number of cells in the offspring. It is of particular interest to understand whether and how epigenetic information can be passed on from the gametes to the embryo or offspring, and whether abnormalities in this process could lead to transgenerationally inheritable phenotypes. The aim of this review is to highlight recent progress made in understanding the nature and mechanisms of epigenetic remodelling that ensue after fertilisation.

Metabolomic prediction of pregnancy viability in superovulated cattle embryos and recipients with fourier transform infrared spectroscopy

We analyzed embryo culture medium (CM) and recipient blood plasma using Fourier transform infrared spectroscopy (FTIR) metabolomics to identify spectral models predictive of pregnancy outcome. Embryos collected on Day 6 from superovulated cows in 2 countries were individually cultured in synthetic oviduct fluid medium with BSA for 24 h before embryo transfer. Spent CM, blank controls, and plasma samples (Day 0 and Day 7) were evaluated using FTIR. The spectra obtained were analyzed. The discrimination capability of the classifiers was assessed for accuracy, sensitivity (pregnancy), specificity (nonpregnancy), and area under the ROC curve (AUC). Endpoints considered were Day 60 pregnancy and birth. High AUC was obtained for Day 60 pregnancy in CM within individual laboratories (France AUC = 0.751 ± 0.039, Spain AUC = 0.718 ± 0.024), while cumulative data decreased the AUC (AUC = 0.604  ±  0.029). Predictions for CM at birth were lower than Day 60 pregnancy. Predictions with plasma at birth improved cumulative over individual results (Day 0: France AUC = 0.690 ± 0.044; Spain AUC < 0.55; cumulative AUC = 0.747 ± 0.032). Plasma generally predicted pregnancy and birth better than CM. These first results show that FTIR metabolomics could allow the identification of embryos and recipients with improved pregnancy viability, which may contribute to increasing the efficiency of selection schemes based on ET.

Incidence of abnormal offspring from cloning and other assisted reproductive technologies

In animals produced by assisted reproductive technologies, two abnormal phenotypes have been characterized. Large offspring syndrome (LOS) occurs in offspring derived from in vitro cultured embryos, and the abnormal clone phenotype includes placental and fetal changes. LOS is readily apparent in ruminants, where a large calf or lamb derived from in vitro embryo production or cloning may weigh up to twice the expected body weight. The incidence of LOS varies widely between species. When similar embryo culture conditions are applied to nonruminant species, LOS either is not as dramatic or may even be unapparent. Coculture with serum and somatic cells was identified in the 1990s as a risk factor for abnormal development of ruminant pregnancies. Animals cloned from somatic cells may display a combination of fetal and placental abnormalities that are manifested at different stages of pregnancy and postnatally. In highly interventional technologies, such as nuclear transfer (cloning), the incidence of abnormal offspring continues to be a limiting factor to broader application of the technique. This review details the breadth of phenotypes found in nonviable pregnancies, together with the phenotypes of animals that survive the transition to extrauterine life. The focus is on animals produced using in vitro embryo culture and nuclear transfer in comparison to naturally occurring phenotypes.

Maternal endometrial oedema may increase perinatal mortality of cloned and transgenic piglets

The perinatal mortality of cloned animals is a well-known problem. In the present retrospective study, we report on mortality of cloned transgenic or non-transgenic piglets produced as part of several investigations. Large White (LW) sows (n = 105) received hand-made cloned LW or minipig blastocysts and delivered either spontaneously or after prostaglandin induction followed by either Caesarean section or vaginal birth. The overall pregnancy rate was 62%, with 26% of pregnancies terminating before term. This resulted in 48 deliveries. The terminated pregnancies consisted of 12 abortions that occurred at 35 ± 2 days gestation and five sows that went to term without returning to heat and then by surgery showed the uterus without fetal content. The gestation length was for sows with LW piglets that delivered by Caesarean section or vaginally was 115.7 ± 0.3 and 117.6 ± 0.4 days, respectively. In sows with minipiglets, the gestation length for those delivered by Caesarean section or vaginally 114.4 ± 0.2 and 115.5 ± 0.3 days, respectively. Of the 34 sows that delivered vaginally, 28 gave birth after induction, whereas 6 farrowed spontaneously. Of the 14 sows that delivered after Caesarean section and in the five empty sows, the endometrium and placenta showed severe oedema. Piglet mortality following vaginal delivery was higher than after Caesarean section (31% v. 10%, respectively; P < 0.001). When vaginal delivery occurred spontaneously, the stillborn rate was greater than after induced delivery (56% v. 24%, respectively; P < 0.0001). Internal organ weights were recorded for seven cloned LW piglets and six normal piglets. The relative weight of the heart, liver, kidneys and small intestine was found to be reduced in the cloned piglets (P < 0.05). The present study demonstrates extensive endometrial oedema in sows pregnant with cloned and transgenic piglets, as well as in empty recipients, at term. The growth of certain organs in some of the cloned piglets was reduced and the rate of stillborn piglets was greater in cloned and transgenic piglets delivered vaginally, possibly because of oedema of the fetal-maternal interface.

Effect of polyvinylpyrrolidone on bovine oocyte maturation in vitro and subsequent fertilization and embryonic development

The exact role of polyvinylpyrrolidone (PVP) in culture medium for oocyte maturation is still largely unknown. Bovine cumulus-oocyte complexes (COC) were cultured in in-vitro maturation (IVM) medium supplemented with 10% fetal bovine serum (FBS), 0.3% PVP (K-90) or 10% serum substitute supplement (SSS) respectively. The rates of oocyte maturation, fertilization and early embryonic development were evaluated. In addition, the status of DNA fragmentation in the oocytes was determined by comet assay, and the ratio of trophectoderm (TE) cells and inner cell mass (ICM) in blastocysts was determined by differential staining. Furthermore, the percentage of apoptotic cells in the blastocysts was examined by TUNEL assay. The results indicated that the effect of PVP in IVM medium was similar to FBS in terms of oocyte maturation and subsequent embryonic development. However, the addition of SSS in IVM medium retarded further embryonic development and resulted in more oocyte DNA fragmentation and a higher ratio of TE cells and ICM in the blastocysts. However, the number of apoptotic cells in blastocysts was similar among the three groups. These results suggest for the first time that the addition of PVP in oocyte maturation medium is not only a suitable substitute for serum but is also beneficial to in-vitro oocyte maturation.

The effect of electrical field strength on activation and development of cloned caprine embryos

The activation procedure used in nuclear transfer (NT) is one of the critical factors affecting the efficiency of animal cloning. The purpose of this study was to compare the effect of two electrical field strengths (EFS) for activation on the developmental competence of caprine NT embryos reconstructed from ear skin fibroblasts of adult Alpine does. The NT embryos were obtained by transfer of the quiescent fibroblasts at the fourth passage into the enucleated metaphase II (M II) oocytes. Four to five hours after electrical fusion, the NT-embryos were activated by EFS either at 1.67 or at 2.33 kV/cm and immediately incubated in 6-DMAP (2 mM) for 4 h. The cleavage rate of the NT-embryos activated with 2.33 kV/cm was greater than that activated with 1.67 kV/cm after in vitro culture for 18 h (65.6% versus 19.6%, p < 0.001). No pregnancy was found in 14 recipient does after transferring 51 NT embryos at 1-2 cell stages activated with 1.67 kV/cm. In contrast, two of the seven recipients were pregnant and gave birth to three kids after transferring 61 NT embryos at 1-2 cell stages activated by 2.33 kV/cm. The birth weights of three cloned kids were within the normal range of Alpine goats. However, one kid died 1h after birth while the remaining two are still healthy. DNA analysis by polymerase chain reaction (single-strand conformation polymorphism, SSCP) confirmed that the three kids were genetically identical to the nuclear donor.

Embryo technologies and animal health – consequences for the animal following ovum pick-up, in vitro embryo production and somatic cell nuclear transfer

Mammalian reproductive technologies that aim either to complement or to transcend conventional livestock breeding options have contributed to some of the most remarkable achievements in the field of reproductive biology in recent decades. In so doing they have extended our horizons in two distinct dimensions, the first concerning what it is technically possible to achieve and the second relating to the time-frame within which an individual's life-long developmental capability is initially established and ultimately realized or undermined. Our impressions of the benefits and values, or otherwise, of technologies such as in vitro embryo production and nuclear transfer are rightly influenced by the extent to which they impinge on the health of animals either subjected to or derived from them. Here, we consider some of the health implications of oocyte/embryo-centric technologies applied to farm livestock.

Errors in development of fetuses and placentas from in vitro-produced bovine embryos

In vitro systems for oocyte maturation, fertilization and embryo culture [in vitro production (IVP)] have the potential for more wide-spread use in creative breeding programs for dairy and beef cattle. However, one negative consequence of both IVP and somatic cell nuclear transfer (SCNT) in cattle and other species is that embryos, fetuses, placentas, and offspring can differ significantly in morphology and developmental competence compared with those from embryos produced in vivo. Fetuses and placentas derived from IVP and SCNT embryos may fall within the normal range of development, may have obvious abnormalities such as increased fetal and placental weights, or may have subtle abnormalities such as aberrant development of fetal skeletal muscle, placental blood vessels, and altered metabolism. Failures in physiologic and/or genetic mechanisms essential for proper fetal growth and survival outside of the uterus contribute significantly to pregnancy and neonatal losses. Oversized fetuses are at increased risk of death during parturition and the adverse consequences of severe dystocia may compromise the dam. Collectively, these abnormalities have been referred to as 'large offspring syndrome' or 'large calf syndrome'. Abnormal phenotypes resulting from IVP and SCNT embryos are stochastic in occurrence and they have not been consistently linked to aberrant expression of single genes or specific pathophysiology. Thus, reliable methods of early diagnosis of the condition are not yet available. The objective of this paper is to examine abnormal development of fetuses and placentas resulting from embryos produced using in vitro systems. The term 'abnormal offspring syndrome (AOS)' is introduced and a classification system of developmental outcomes is proposed to facilitate research efforts on the mechanisms of the various abnormal phenotypes. We also discuss potential genetic and physiologic mechanisms that may contribute to abnormal phenotypes following transfer of IVP and SCNT embryos.

The Impact of Nutrition of the Cumulus Oocyte Complex and Embryo on Subsequent Development in Ruminants

Cumulus-oocyte complexes (COCs) and early embryos rely on a histotrophic nutrition source for energy production and the synthesis of macromolecules. There is accumulating evidence suggesting that the balance of supply and demand for energy and other anabolic substrates during oocyte maturation and very early stages of development programmes subsequent developmental potential, and this may include subsequent fetal growth trajectory. One example is the role of glucose (Glc) during cumulus-oocyte complex maturation. Glucose is an essential nutrient for maturation, especially its role during cumulus expansion. Our laboratory has shown that during in vitro culture, too little glucose during cumulus-oocyte complex maturation affects meiotic competence. We have focussed on glucose (Glc) metabolism through the hexosamine biosynthesis pathway (HBP) during COC maturation in vitro. The HBP in somatic cells is regarded as a "fuel-sensing" pathway and its interaction with cell signalling systems and transcriptional regulation is increasingly apparent. Up-regulation of the HBP during oocyte maturation in vitro has negative consequences for subsequent development. Another example is the role of hypoxia (low O2) during peri-compaction development. My laboratory believes that ruminant embryos during compaction, blastulation and subsequent development in the uterine cavity lack a key hypoxia responsive element. Because of this, hypoxia is important for normal development in ruminants but perturbs further development in rodents. The implication of these examples to the fundamental concept of peri-conception nutritional programming of development are discussed.

An approach for producing transgenic cloned cows by nuclear transfer of cells transfected with human alpha 1-antitrypsin gene

In an attempt to produce transgenic cloned cows secreting alpha 1-antitrypsin (alpha1-AT) protein into milk, bovine cumulus cells were transfected with a plasmid containing an alpha1-AT gene and green fluorescent protein (GFP) reporter gene using Fugene 6 as a lipid carrier. The GFP-expressing cells were selected and transferred into enucleated bovine oocytes. Couplets were fused, chemically activated and cultured. Developmental competence was monitored and the number of inner cell mass (ICM) and trophectoderm (TE) cells in blastocysts were counted after differential staining. The percentage of blastocysts was lower (P < 0.05) in transgenic cloned embryos compared to non-transgenic cloned embryos (23% versus 35%). No difference in the numbers of ICM and TE cells between the two groups of embryos was observed. One or two GFP-expressing blastocysts were transferred into the uterus of each recipient cow. Out of 49 recipient cows, three pregnancies were detected by non-return estrus and rectal palpation. However, the pregnancies failed to maintain to term; two fetuses were aborted at Day 60 and 150, respectively, and one fetus at Day 240. The genomic DNA from the aborted fetus was amplified by polymerase chain reaction (PCR) to investigate integration of the transgene in the fetus. The expected PCR product was sequenced and was identical to the sequence of alpha1-AT transgene. In conclusion, the present study demonstrated that developmental competence of cloned embryos derived from transgenic donor cells was lower than embryos derived from non-transfected donor cells. Although we failed to obtain a viable transgenic cloned calf, integration of alpha1-AT gene into the fetus presents the possibility of producing transgenic cloned cows by somatic cell nuclear transfer.

In Vitro Embryo Production: Growth Performance, Feed Efficiency, and Hematological, Metabolic, and Endocrine Status in Calves

The potential management benefits of in vitro embryo production have been offset by an increased incidence of health-related problems in resulting calves [increased birth weight, congenital abnormalities, and peri- and postnatal mortality (large-offspring syndrome)] and of recipient cows (prolonged gestation, dystocia, increased hydroallantois, abortion). The aim of the present research was to determine whether relevant metabolic, endocrine, or hematological traits could be related to the causes of enhanced growth performance of in vitro fertilized calves. Growth performance and feed efficiency as well as hematological, metabolic, and endocrine traits studied in calves derived from in vitro-produced embryos (IVP; n = 11) and in calves derived from artificial insemination (AI; n = 8). Donor cows from which oocytes for in vitro fertilization were obtained had a heterogeneous background, thus excluding genetic maternal influences. On the other hand, semen for in vitro fertilization and for artificial insemination was from the same bull, and recipient cows were held under the same husbandry and feeding conditions as AI cows, thus reducing the variability. Blood samples were collected preprandially on d 1, 2, 3, 4, 7, 14, 28, 56, and 112 of life and every 20 min between 0830 and 1630 h on d 7 and 112 for the evaluation of growth hormone secretory patterns. Gestation of IVP cows was longer than that of AI cows, but birth weights were similar in both groups. Feed intake, average daily gain, and body length during the experimental period, body weight from wk 8 to 16, and gain/feed ratio during the first month of life were higher in IVP than in AI calves. At birth, potassium, 3,5,3'-triiodothyronine, and thyroxine concentrations were lower in IVP than in AI calves. Concentrations of sodium and potassium on d 7, of triglycerides on d 28, and of albumin on d 56 were higher in IVP than in AI calves. In conclusion, IVP calves had higher feed intake and growth rate during the entire growth period and improved feed efficiency in the first month of life than AI calves, but this was not mirrored by consistent changes of hematological, metabolic, or endocrine traits, whose concentrations were in the normal range. Additional work is needed to study IVP calves under field conditions.

Plasma concentrations of bovine pregnancy-associated glycoprotein (bPAG) do not differ during the first 119 days between ongoing pregnancies derived by transfer of in vivo and in vitro produced embryos

Calves derived from IVP embryos may suffer from the large offspring syndrome that has been related to effects of in vitro culture on the intrinsic quality of the embryo. Limited information is available on the role of the placenta in such cases. In this study, bovine pregnancy-associated glycoprotein (bPAG) was used as a marker to test whether placental function is influenced by the route of embryo production. Therefore, from day 7 until day 119 of ongoing gestations, resulting from transfer of MOET (n = 53), IVP-co-culture (n = 21) and IVP-SOF (n = 38) embryos, bPAG levels were compared in peripheral plasma of recipients. Plasma progesterone levels were compared as well. From day 25 of gestation onwards, bPAG could be detected in all recipients and the levels were significantly influenced by the day of gestation. Although IVP calves were significantly heavier than the in vivo produced calves, this difference was not reflected in the bPAG profiles of the embryo production groups. Yet, the mean bPAG level of the three last sampling moments (days 105-119) tended to be positively related to the birth weight of the calves, irrespective of the embryo production technique. Progesterone concentrations were not influenced by route of embryo production, but were significantly affected by parity of the recipient and day of gestation.

Epigenetic reprogramming throughout preimplantation development and consequences for assisted reproductive technologies

Knowledge about preimplantation development is important both for basic reproductive biology and for practical applications, including livestock breeding and regenerative medicine. During preimplantation development, epigenetic modifications such as DNA methylation and histone modifications are involved in the regulation of imprinted and non-imprinted genes, in the initiation of X chromosome inactivation, and the adjustment of telomere length. The underlying events are particularly vulnerable to external factors. Characterization of expression profiles in in vivo-derived embryos of different developmental stages and understanding the mechanisms and dynamics underlying the reprogramming process are the first steps towards the analysis of the complex gene regulatory networks. They provide a baseline for the analysis of manipulated embryos of all mammalian species, including humans, to improve embryo technologies and related therapeutic applications.

Ultrasonographic Monitoring of Nuclear Transferred Fetal Weight during the Final Stage of Gestation in Holstein Cows

Dystocia or stillbirth accompanied by Large Offspring Syndrome (LOS) occurs rather frequently in Holstein nuclear transferred calves. In regard to prophylaxes, nuclear transferred Holstein fetuses were monitored with ultrasonography during the final stage of gestation. Fetal weight was estimated weekly based on the fetal metacarpal width using ultrasonography. Fourteen Holstein cows pregnant with Holstein nuclear transferred fetuses were the subjects of this experiment. The fetal weight was estimated by measuring the fetal metacarpal width during the last month of gestation according to the expected date of parturition. Measurements were performed on a weekly basis. The ultrasound-estimated metacarpal width and body weight of 13 of the fetuses in the last week of gestation (30.2+/-2.2 mm, 50.0+/-4.7 kg) were similar to the actual measurement immediately after birth (30.0+/-2.1 mm, 51.2+/-5.5 kg). These results indicate that ultrasonographic monitoring within a week of parturition to is accurate for estimating fetal weight. Prediction of LOS with ultrasonography contributes to reliable a diagnostic method that minimizes syndrome-related gyneco-obstetric complications at parturition with the aid of appropriate treatments.

Rate of abnormalities in lambs from in vitro produced embryos transferred on Day 2 compared with Day 6 postfertilization

The effect of transferring ovine IVP embryos on Day 2 versus Day 6 postinsemination was investigated. Oocytes were collected from 35 cull ewes and cultured separately for each donor. Embryos were exposed to serum in the maturation and fertilization media, and then cultured in a serum-free SOF system under serum-conditioned silicone oil. Cleaved Day 2 postfertilization embryos were randomly allocated for immediate transfer versus Day 6 transfer. Parturition was induced (with 15 mg dexamethasone) between Days 141 and 143 of pregnancy; those failing to initiate parturition by Day 146 had a Caesarean section. Stillborn lambs and those dying within several days of birth were necropsied. Lambs were weighed at birth; lambs (n = 132) derived from the same flock (from natural breeding or AI) were used as a control. An estimate of the 99th percentile of the normal population was used as the point above which lambs from three litter-size categories were classified as abnormally large (analysis was repeated for 95% confidence and median estimates of this value). Thirty-eight lambs were born from early transfer, 45 from late transfer and 12 from unobserved lambings (parentage could not be determined). Lambs from early transfer were heavier at birth (P = 6.0 x 10 (-11)). The early treatment group had fewer lambs produced per embryo transferred (P = 0.0002), fewer live lambs per embryo transferred (P = 0.00009) and fewer normal lambs per embryo transferred (P= 0.0002). There was an effect of donor on the number of dead lambs per embryo transferred (P = 0.017). The number of dystocias per transfer was not significantly different for early versus late transfer groups. However, the probabilities of survival for cleaved embryos were 27.3% and 13.1% in the early and late transfer treatment, respectively. There were more lambs produced per cleaved embryo with early transfer (P = 0.004) and there was an effect of donor within ram and replicate (P = 0.04) on the number of lambs produced. The odds ratio for early/late treatment was 2.449 with a confidence interval of 1.368-4.382. Day 2 transfer of cleaved embryos did not prevent the production of oversized or abnormal offspring; however, there was an increased chance of a cleaved embryo producing a lamb when transferred on Day 2 rather than Day 6 postfertilization.

No peri- and postnatal effects on calves born after transfer of in vitro produced embryos vitrified by the open pulled straw (OPS) method

The general objective of this study was to perform follow-up studies including selected peri- and postnatal characteristics on calves born after transfer of in vitro produced (IVP) embryos vitrified by the 'Open Pulled Straw' (OPS) method. An overall pregnancy rate of 16% after transfer of the OPS-vitrified IVP embryos was achieved and resulted in birth of 9 calves, with 11 AI calves serving as controls. There were no immediate or long-term effects on these calves with respect to birth weight, gestation length, perinatal mortality, growth rate, disease susceptibility and reproductive performance.

In vitro production of bovine embryos and their application for embryo transfer

This review introduces newly developed serum-free media (IVD101 and IVMD101), that are effective for producing high yields of transferable embryos of good quality from in vitro-matured and -fertilized oocytes. Both serum-free media produced better results than serum-containing medium, including increased rates of blastocyst formation, post-thaw embryo viability, and pregnancy after transfer. In addition, reduced risks of calf mortality and large calf syndrome were also observed for the serum-free-derived embryos. Serum-derived embryos contained a large number of lipid droplets and immature mitochondria in their cytoplasm that may account for the lower production of transferable embryos and poor embryo quality. A non-invasive technique using scanning electrochemical microscopy was successful in quantitatively measuring oxygen consumption of single embryos. This technique may prove to be reliable for predicting embryo viability and subsequent developmental ability.

Improving successful pregnancies after embryo transfer

Over the past 20 years the rate of blastocyst development in vitro has improved through the development of sequential defined media, refining the oxygen concentrations during culture and providing substrates to ameliorate free radical accumulation. Despite these advances there has been little progress in improving calving rates after the transfer of in vitro produced embryos. This suggests that the culture conditions have been very effective in enabling those fertilised oocytes to reach the blastocyst stage that otherwise would not occur in vivo. We suggest that the next advance by which the embryo transfer technology gains more acceptance in cattle production will be identifying those cows which are intrinsically superior recipients. This must be coupled to the development of non-invasive assessments of the developmental competence of both the oocyte and the blastocyst. Until these two goals are achieved the ET industry will remain static and unable to overcome the economic loss caused by embryo mortality occurring 7-10 days after transfer.

Evaluation of Bovine Embryos Produced in High Performance Serum-Free Media

This review evaluates the quality of bovine embryos developed from in vitro-matured (IVM) and -fertilized (IVF) oocytes cultured in either serum-free or serum-containing media. Bovine embryos cultured in serum-supplemented medium contain numerous cytoplasmic lipid droplets and immature mitochondria compared to those cultured in serum-free medium. The accumulation of cytoplasmic lipids in embryos developed in serum-containing medium may be a result of incorporation of lipoproteins from the serum and may result in impaired function of mitochondria. The improved serum-free media (IVMD101 and IVD101) offer several advantages over culture in serum-containing medium, including increased rates of blastocyst formation and higher cell numbers. Additionally, the survival and hatching rates of embryos produced in serum-free media after post-thaw culture were superior to those of embryos produced in the serum-containing medium, suggesting that the abnormal accumulation of cytoplasmic lipids in embryos may have a negative effect on the sensitivity of embryos to chilling and freezing. These serum-free culture systems have proven to be beneficial for the production of good quality embryos from IVM-IVF bovine oocytes. Furthermore, recent studies have shown a correlation between mitochondrial function (oxygen consumption) and embryo quality. A new method using scanning electrochemical microscopy may be capable of assessing the viability and developmental potential of bovine embryos.

Commercialization of animal biotechnology

Commercialization of animal biotechnology is a wide-ranging topic for discussion. In this paper, we will attempt to review embryo transfer (ET) and related technologies that relate to food-producing mammals. A brief review of the history of advances in biotechnology will provide a glimpse to present and future applications. Commercialization of animal biotechnology is presently taking two pathways. The first application involves the use of animals for biomedical purposes. Very few companies have developed all of the core competencies and intellectual properties to complete the bridge from lab bench to product. The second pathway of application is for the production of animals used for food. Artificial insemination (AI), embryo transfer, in vitro fertilization (IVF), cloning, transgenics, and genomics all are components of the toolbox for present and future applications. Individually, these are powerful tools capable of providing significant improvements in productivity. Combinations of these technologies coupled with information systems and data analysis, will provide even more significant change in the next decade. Any strategies for the commercial application of animal biotechnology must include a careful review of regulatory and social concerns. Careful review of industry infrastructure is also important. Our colleagues in plant biotechnology have helped highlight some of these pitfalls and provide us with a retrospective review. In summary, today we have core competencies that provide a wealth of opportunities for the members of this society, commercial companies, producers, and the general population. Successful commercialization will benefit all of the above stakeholders.

Improving delivery and offspring viability of in vitro-produced and cloned sheep embryos

Recently developed, assisted reproductive technologies (e.g., in vitro embryo production and nuclear transfer) have encountered perinatal morbidity/mortality of the offspring produced, which are likely to hinder the application of these techniques. Consequently we have sought to develop a system of hormonal stimulation that will ensure the delivery of offspring more prepared for extrauterine life. Here we examine deliveries outcome in sheep carrying in vitro-produced and nuclear transfer (NT) embryos in comparison to artificially inseminated and naturally mated control ewes. All groups (excluding NT, which received one treatment) were subjected to one of two hormonal treatments for induction of delivery, whereas the third part of each group was left without any treatment. The first (commonly used for naturally mated ewes) dexamethasone treatment did not solve a majority of parturition disturbances, and actually the number of deliveries necessitating assistance was reduced (P < 0.05) by this treatment in the control group. On the other hand, combined estradiol plus betamethasone stimulation (E + B) solved a majority of complications regarding delivery performance such as lack of the preparation of the mammary gland, low myometrial contractility, insufficient cervical ripening, and impaired maternal behavior. Moreover, substantial reduction of neonatal mortality was observed following the combined treatment. In conclusion, the E + B induction of delivery overcame the majority of physiological and behavioral intrapartum failures of sheep foster mothers and increased the survival of offspring, and thus can be recommended as a safe method for inducing delivery in foster mothers carrying in vitro-generated embryos.

Effects of beta-endorphin and Naloxone on in vitro maturation of bovine oocytes

Bovine cumulus-oocyte complexes (COCs) and mural granulosa cells express the mRNA coding for the micro-opioid receptor. The addition of beta-endorphin (beta-end) to oocytes cultured in hormonally-supplemented in vitro maturation (IVM) medium had no effect on the rates of oocytes reaching the metaphase II (MII) stage, but significantly decreased the maturation rate (P < 0.05) and arrested oocytes at metaphase I (MI) after culture in hormone-free medium (P < 0.001). Naloxone (Nx) reverted this inhibitory effect of beta-end. Moreover, Nx "per se" showed a dose-dependent dual effect. When added at high concentration (10 x (-3) M), it significantly reduced the rate of oocytes in MII (P < 0.001), thus increasing the rate of oocytes arrested in MI. However, Nx added at low concentration (10 x (-8) M) significantly increased oocyte maturation (P < 0.001). High concentration of Nx induced an increase in both intracellular calcium concentration ([Ca(2+)](i)) and in the activity of the mitogen-activated protein kinase (MAPK) also called extracellular-regulated kinase (ERK) in cumulus cells of bovine COCs. Blocking the rise in [Ca(2+)](i) with the calcium chelator acetoxymethylester-derived form of bis (o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM) reversed the Nx-dependent inhibition of meiotic maturation observed at high Nx concentrations. Whereas blocking ERK with the MAPK/ERK kinase (MEK) inhibitor, PD98059, had no effect on this process. Therefore, we concluded that the mocro-opioid receptor, by inducing [Ca(2+)](i) increase, participates in the cumulus-oocyte coupled signaling associated with oocyte maturation.

Aberrant allocations of inner cell mass and trophectoderm cells in bovine nuclear transfer blastocysts

Abortions of nuclear transfer (NT) embryos are mainly due to insufficient placentation. We hypothesized that the primary cause might be the aberrant allocations of two different cell lineages of the blastocyst stage embryos, the inner cell mass (ICM) and the trophectoderm (TE) cells. The potential for development of NT embryos to blastocysts was similar to that for in vitro fertilized (IVF) embryos. No difference in the total cell number was detected between NT and IVF blastocysts, but both types of embryos had fewer total cells than did in vivo-derived embryos (P < 0.05). The NT blastocysts showed a higher ratio of ICM:total cells than did IVF or in vivo-derived embryos (P < 0.05). Individual blastocysts were assigned to four subgroups (I: <20%, II: 20-40%, III: 40-60%, IV: >60%) according to the ratio of ICM:total cells. Most NT blastocysts were placed in groups III and IV, whereas most IVF and in vivo-derived blastocysts were distributed in group II. Our findings suggest that placental abnormalities or early fetal losses in the present cloning system may be due to aberrant allocations of NT embryos to the ICM and TE cells during early development.

Bovine embryos contain a higher proportion of polyploid cells in the trophectoderm than in the embryonic disc

The frequency of polyploid cells in the embryonic disc (ED) and in the trophectoderm (TE) was assessed in 50 in vitro produced bovine embryos fixed at days 7-8 post insemination (pi) and in 20 in vitro produced embryos that were transferred to uteri of recipients at day 7 and then recovered and fixed at day 12 pi. Separation of TE and ED cells was obtained by microdissection and the frequency of polyploid cells was determined by interphase cytogenetic analysis using fluorescence in situ hybridization (FISH) with chromosome 6- and chromosome 7-specific probes. The results show that 96% of day 7 embryos contain polyploid cells in the TE, whereas only 58% contain polyploid cells in the ED. In day 12 embryos 85% of TE and 40% of ED preparations contain polyploid cells. Statistical analysis revealed that the frequency of polyploid cells was significantly higher in the TE than in the ED in embryos containing less than 25% polyploid cells (n = 65). The few embryos (n = 5), which contained more than 25% polyploid cells, did not show this difference. Further, it was revealed that the level of polyploidy on day 7-8 was significantly higher than on day 12, both in the TE (two-fold) and in the ED (seven-fold).

Macromolecule absorption and cortisol secretion in newborn calves derived from in vitro produced embryos

Earlier reports indicate that calves derived from in vitro produced (IVP) embryos are more susceptible to neonatal disease than calves produced after artificial insemination (AI) or natural mating. The aims of the present study were to investigate whether calves born after IVP embryos show an altered macromolecule absorption (immunoglobulin G (IgG) and porcine serum albumin (PSA)) compared with AI calves and whether the macromolecule absorption could be related to the degree of acidosis or to the cortisol secretion around birth. Hence, IgG and PSA absorption in control AI calves (n=7) was compared with that in two groups of IVP calves (IVP-defined: SOFaa embryo culture with polyvinyl alcohol, n=6; IVP-serum: SOFaa embryo culture with serum and co-culture, n=8). The calves were fed colostrum (40ml/kg) at 2, 6 and 12h after birth. At 24h after birth, both AI and IVP calves had achieved a level of plasma IgG sufficient to provide passive immunization (>15mg/ml). When the values were adjusted for the varying colostral IgG contents and the degree of acidosis, the IVP-defined calves had significantly lower peak plasma IgG concentrations than the AI calves at 18-24h after birth (P<0.04). However, when the macromolecule marker (PSA), was fed to all calves at 2 and 12h after birth the resulting plasma PSA levels were significantly lower in the AI calves compared with the IVP calves during the whole observation period (P<0.0001). Calves with a moderate neonatal acidosis (mean pH<7.2 during the first 30min after birth) had reduced peak plasma IgG concentration at 18-24h after birth (P<0.02) compared to calves without acidosis. The basal and ACTH-stimulated cortisol levels were lower in the newborn IVP-defined calves than in the AI calves (P<0.05) and the IVP-serum calves (P<0.002). Cortisol levels shortly after birth correlated positively with birth weight (r=0.60, P<0.0001) and with gestation length (r=0.34, P<0.04). Since, the IVP calves absorbed sufficient amounts of IgG from colostrum to acquire sufficient passive immunity, we conclude that the lower viability described in IVP offspring probably is not caused by an impaired passive immunization. IVP-defined calves had significantly lower absorption efficiency of IgG compared with AI calves, whereas absorption of a non-Ig macromolecule (PSA) was higher for IVP than AI calves. This might indicate a more selective absorption in AI calves in favor of IgG. Acidosis around birth affected immunoglobulin absorption negatively. IVP-defined calves had significantly lower cortisol levels the first 3h after birth and during an ACTH-challenge and a lower IgG absorption efficiency, which might indicate a mild degree of organ dysmaturity in these calves.

Effects of in vivo prematuration and in vivo final maturation on developmental capacity and quality of pre-implantation embryos

In current in vitro production (IVP) systems, oocytes lack in vivo dominant and preovulatory follicular development, which may compromise pregnancy and viability of calves born. When an oocyte sets off in vivo on the road toward fertilization, it contains numerous transcripts and proteins necessary to survive the first few cell cycles of embryonic development. It is not yet known during which period of development the oocyte builds up the store, possibly primarily during the major growth phase of the oocyte, which is completed at the time a follicle reaches the size of 3 mm. Here, we investigated to what extent the later phases of follicular development, such as prematuration in the dominant follicle before the LH surge and ensuing final maturation in the preovulatory follicle, contribute to oocyte competence and development into viable biastocysts. Recent studies on in vivo vs in vitro oocyte maturation employed oocytes from an identical preovulatory development by applying ovum pick-up (OPU) twice (before and 24 h after the LH surge) in each cow treated for superovulation with a controlled LH surge. The embryo recovery rates at Day 7 of IVC after IVF were similar: 44% (97/219) for in vivo- vs 41% (87/213) for in vitro-matured oocytes, which shows that the natural environment during final maturation is not essential for the mere in vitro development of the prematured oocyte beyond the 8- to 16-cell stage. However, in vivo maturation appeared to contribute to the oocyte's quality in a more subtle way, as indicated by a significant increase in the proportion of expanded blastocysts and a more physiological degree of chromosome aberrations of the embryos. In blastocysts derived from in vivo-matured oocytes, 21% of the embryos were mixoploid vs 50% from in vitro-matured oocytes, concomitant with a higher number of cells (96 vs 54 per normal blastocyst). The expression pattern of a set of six developmentally important genes was, however, not significantly altered in blastocysts derived from in vivo-matured oocytes. Certain deviations were observed compared with the levels of entirely in vivo-developed control blastocysts, which suggests that the beneficial effects of in vivo maturation are possibly exerted at initial stages of embryonic development. Prematuration in vivo, occurring in a dominant follicle developing from about 8 mm into the preovulatory follicle, is accompanied by changes in protein synthesis of the cumulus oocyte complex (COC). Presumably, the differentially expressed proteins are involved in equipping the oocyte with further developmental competence. Although we have unraveled some important biochemical and cellular biological features of the oocyte, further research on in vivo processes is essential to improve in vitro embryo production in practice.

Cloned transgenic offspring resulting from somatic cell nuclear transfer in the goat: oocytes derived from both follicle-stimulating hormone-stimulated and nonstimulated abattoir-derived ovaries

The use of nuclear transfer (NT) techniques to create transgenic offspring capable of producing valuable proteins may have a major impact on the pharmaceutical market. Our objective was to compare the in vivo developmental potential of NT embryos produced from the fusion of transgenic donor cells with cytoplasts prepared from either FSH-stimulated ovaries or nonstimulated abattoir-derived ovaries. Donor cells were prepared from a transgenic fetus carrying the gene for human antithrombin III as a marker and used within four to eight subpassages. Cells were serum deprived for 4 days prior to cytoplast transfer. Oocytes were enucleated by removing the metaphase plate using a DNA stain and epifluorescent illumination. Donor cells were fused to enucleated oocytes by electric pulse and then chemically activated. There was no difference in the number of transferable embryos produced from cytoplasts of FSH-stimulated ovaries or from the fusion of cytoplasts from abattoir ovaries, nor was there a difference in the number of pregnancies established per recipient with either treatment. All pregnancies from both groups culminated in the births of healthy female kids (five total). To our knowledge, this is the first report of cloned goats produced from NT using cytoplasts derived from abattoir ovaries.

Characteristics of Korean native, Hanwoo, calves produced by transfer of in vitro produced embryos

The main objectives of this investigation were to monitor the birth weight of calves and gestation length following artificial insemination (AI) and transfer of in vivo or in vitro produced Korean native, Hanwoo embryos. Embryos produced in vivo were recovered from uterine flushings of superovulated cows 7 days after AI. Those embryos produced in vitro were co-cultured with cumulus cells for 7-8 days after in vitro fertilization. The birth weights of calves following the transfer of in vitro produced (IVP) embryos were heavier than calves from both of AI- and in vivo-derived embryo transferred calves in both sexes (29.6, 24.1 and 25.2kg, respectively, P<0.05). The IVP calves also had a longer gestation length (293.9, 285.8 and 283.8 days, respectively, P<0.05).

Transgenic production from in vivo-derived embryos: effect on calf birth weight and sex ratio

We examined transgenic-cattle production by DNA microinjection into 1-, 2-, and 4-cell embryos, analyzing the impact on calf size and subsequent viability. Embryos were either collected at an abattoir by flushing oviducts from superovulated and artificially inseminated cows (in vivo-derived) or obtained by in vitro maturation and in vitro fertilization of oocytes aspirated from excised ovaries (in vitro-derived). A human serum albumin (hSA) milk-expression DNA construct was microinjected, either in one of the visible pronuclei of in vitro- and in vivo-derived 1-cell embryos or in the nuclei of two blastomeres of 2- and 4-cell in vivo-derived embryos. Microinjection-induced mortality (lysis and developmental block) was equivalent ( approximately 40%) for all microinjected embryos. Embryos were co-cultured with BRL cells in B-2 medium containing 10% fetal calf serum (FSC). Overall, embryo development to morulae/blastocysts was significantly greater for in vivo-derived ova (15.5%) than for in vitro-derived oocytes (9.3%). All morulae and blastocysts were transferred to synchronized recipient females on Days 6-8 post-fertilization. A total of 189 calves were delivered. Birth weights were significantly greater for calves generated from in vitro-derived oocytes compared with those generated from in vivo-derived oocytes. One transgenic bull calf was obtained from the microinjection of a 2-cell embryo. Fluorescence in situ hybridization (FISH) analysis of lymphocytes detected one transgenic integration site in all cells. Transmission frequency of the hSA transgene in embryos obtained through IVM/IVF/IVC utilizing the semen of the transgenic calf confirmed that it was not mosaic.

DNA damaging agents increase gadd153 (CHOP-10) messenger RNA levels in bovine preimplantation embryos cultured in vitro

DNA damage and other forms of stress are believed to be important factors in reducing the efficiency of in vitro embryo transfer techniques in farm animals. The expression of mRNAs from stress-responsive genes such as gadd153 (CHOP-10, ddit3) may provide a means of assessing the quality of embryos produced in vitro. Treatment of bovine granulosa cell cultures with the DNA-damaging agents, methyl methane-sulphonate (MMS) or sodium arsenite, induced the expression of an mRNA, which hybridized with the hamster gadd153 cDNA. Part of the corresponding bovine cDNA was amplified by nested polymerase chain reaction (PCR), cloned, and sequenced. Using a sensitive reverse transcriptase-PCR assay we have investigated the expression of gadd153 and beta-actin in blastocyst-stage bovine embryos treated with MMS or sodium arsenite. Both agents produced an increase in the ratio of gadd153 mRNA relative to beta-actin. These results show that there are changes in gene expression in blastocyst-stage bovine embryos in response to genotoxic stress, suggesting that an increase in gadd153 mRNA is a useful marker of DNA damage and metabolic stress in preimplantation embryos.

Compromised development of calves ( ) derived from in vitro-generated embryos and transferred interspecifically into domestic cattle ( )

Advanced reproductive technologies, incuding IVF and interspecies embryo transfer, are becoming increasingly important for the preservation of endangered species. Previous attempts at interspecies transfers between Bos gaurus and Bos taurus have yielded compromised offspring. The goal of this investigation was to characterize the effects of interspecies transfer of IVF-derived embryos on subsequent neonatal outcome. To achieve this goal, fresh Bos gaurus IVF-derived embryos were transferred into Holstein (Bos taurus) recipients. Four fetuses were carried to term. Calf weight, temperature, heart rate, and respiration rate were recorded after birth. Blood samples also were obtained for determination of blood glucose, pH, packed cell volume (PCV), total hemoglobin (tHB), PO2, and PCO2. After parturition, milk production and health status of the recipients were recorded. Two calves were alive at birth, and two calves were stillborn. One of the calves that was born alive died within minutes after birth, while the other lived until approximately 26 h of age. Blood samples obtained from the calf that lived for 26 h showed it to be extremely acidotic and hypoglycemic; this calf also had marked difficulty thermoregulating. At necropsy, all calves showed evidence of in utero gasping and hypoxia, suggestive of premature placental separation. None of the recipient cows showed typical signs of impending parturition. After parturition, lactogenesis in all recipient cows was markedly decreased. On gross examination, placentae resulting from the interspecies transfers had fewer cotyledons that were also much larger in size compared to cotyledons from normal gaur placentae. Calves in this study had abnormalities consistent with those noted from previous interspecies transfers and with IVF and nuclear transfer (cloned) calves. Due to the design of this study, it is not possible to differentiate between problems resulting from the IVF process and those resulting from potential interspecies incompatibilities. However, interspecies transfers of in vitro-produced gaur embryos into Bos taurus are strongly discouraged.

Influence of in vitro systems on embryo survival and fetal development in cattle

In vitro systems are commonly used for the production of bovine embryos. Comparisons between in vivo and in vitro produced embryos illustrate that the morphology of preimplantation-stage embryos differ significantly, the survival of embryos and fetuses is decreased, the size distributions of the populations of conceptuses and fetuses are altered throughout gestation, and placental development is significantly changed. Taken together these findings indicate that exposure to some in vitro environments during the first 7 days of life can profoundly influence fetal and placental development in cattle. An understanding of how in vitro oocyte maturation, in vitro fertilization, and embryo culture systems influence both fetal and placental development should result in systems that consistently produce normal embryos, fetuses, and calves.

Chromosome aberrations in in vitro-produced bovine embryos at days 2-5 post-insemination

Availability of embryos of high quality is required to obtain satisfactory embryonic developmental rates and normal calves following transfer of in vitro-produced (IVP) bovine embryos. One relevant quality parameter is the frequency of chromosome aberrations, which can be evaluated using multicolor fluorescent in situ hybridization (FISH) with chromosome 6- and chromosome 7-specific probes in cattle. In this study, interphase nuclei (n = 3805) were analyzed from 426 bovine IVP embryos. We found that 73%, 72%, 81%, and 58% of the embryos from Days 2, 3, 4, and 5 post-insemination (pi), respectively, displayed a normal diploid chromosome number in all cells. When looking at the types of chromosome aberrations, the percentages of mixoploidy at Days 2, 3, 4, and 5 pi were 22%, 15%, 16%, and 42%, respectively, whereas the percentages of polyploidy (i.e., all nuclei in an embryo were analyzed and were polyploid) were 5%, 13%, 3%, and 0%, respectively. In conclusion, numerical chromosome aberrations were detected as early as Day 2 pi. The development of polyploid embryos is slow and is apparently arrested during the third cell cycle, whereas the mixoploid embryos seem to continue development.