Changes in placental development have been associated with foetal abnormalities after in vitro embryo manipulations. This study was designed to investigate bovine conceptus development and substrate levels in plasma and fluids in in vivo-and in vitro-produced (IVP) concepti and neonates. In vivo-produced and IVP embryos were derived by established embryo production procedures. Pregnant animals from both groups were slaughtered on days 90 or 180 of gestation, or allowed to go to term. Conceptus and neonatal physical traits were recorded; foetal, maternal and neonatal blood, and foetal fluids were collected for the determination of blood and fluid chemistry, and glucose, fructose and lactate concentrations. Placental transcripts for specific glucose transporters were determined by quantitative RT-PCR. No significant differences in uterine and conceptus traits were observed between groups on day 90. On day 180, larger uterine, placental and foetal weights, and an increase in placental gross surface area (SA) in IVP pregnancies were associated with increased glucose and fructose accumulation in foetal plasma and associated fluids, with no differences in the expression of components of the glucose transporter system. Therefore, the enlarged placental SA in IVP pregnancies suggests an increase in substrate uptake and transport capacity. Newborn IVP calves displayed higher birth weights and plasma fructose concentrations soon after birth, findings which appeared to be associated with clinical and metabolic distress. Our results indicated larger concepti and increased placental fructogenic capacity in mid-to late IVP pregnancies, features which appeared to be associated with an enhanced substrate supply, potentially glucose, to the conceptus.

Although a majority of clones are born normal and apparently healthy, mortality rates of nearly 30% are described in many reports. Such losses are a major limitation of cloning technology and represent substantial economic investment as well as justifiable animal health and welfare concerns. Prospective, controlled studies are needed to understand fully the causes of neonatal mortality in clones and to develop preventive and therapeutic strategies to minimize losses. We report here the findings of studies on the hematologic and biochemical profiles of cloned and control calves in the immediate 48-h postpartum period. Cloned calves were similar to control calves for a majority of parameters studied including blood gases, concentrations of plasma proteins, minerals and electrolytes, and white blood cell, neutrophil, lymphocyte, and platelet counts. The most notable differences between clones and controls in this study were reduced red- and white-blood cell counts in clones at birth and 1 h of age. As a group, plasma electrolyte concentrations were more variable in clones, and the variability tended to be shifted either higher (sodium, chloride) or lower (potassium, bicarbonate) than in controls. Previously, we noted differences in carbohydrate parameters, the length of time required for clones to make the neonatal adaptation to life ex utero, and morphology of the cloned placenta. Taken together, our findings suggest that cloned calves experience greater difficulty adjusting to life ex utero and that further research is warranted to determine the nature of the relationship between the physiological differences noted here in clones at birth and concomitant abnormal placental morphology.

The period immediately after birth is a vital time for all newborn calves as the cardiovascular, respiratory, and other organ systems adapt to life ex utero. Reported neonatal mortality rates suggest this period to be especially critical in cloned calves; yet prospective, controlled studies on the physiological status of these calves are lacking. The objectives of this study were to compare neonatal (birth to 48 h of age) physical and clinical characteristics and placental morphology of cloned and embryo transfer control calves delivered by cesarean section after induced labor. All calves were raised under specialized neonatal-care protocols at a large-animal veterinary research and teaching hospital. Cloned calves were similar to controls for many parameters studied. Notable exceptions included developmental delays of important physical adjustment parameters and enlargement of the umbilical region. Placentas associated with cloned calves contained fewer total placentomes, a twofold increase in surface area and mass per placentome, and a shift in placentome morphology toward larger, flatter placentomes. The most striking clinical variations detected in clones were hypoglycemia and hyperfructosemia, both measures of carbohydrate metabolism. Because the placenta is known to be the source of plasma fructose in newborn calves, increased fructose production by the cloned placenta may be an important factor in the etiology of umbilical and cardiac anomalies in clones observed in this and other studies.

The timing of the transition from maternal to zygotic control of development (MZT) and the initiation of transcription was studied in domestic cat embryos to determine if there is a temporal association between these phenomena and the developmental block observed in cat embryos fertilized in vitro. Embryos were derived from in vitro‐matured, in vitro‐fertilized (IVM/IVF) oocytes. In Experiment 1, embryos (n = 52) were cultured continuously in the presence of 10 μg/ml α‐amanitin (a transcriptional inhibitor) from 12‐hr postinsemination (hpi), and cleavage stage was evaluated every 24 hr. The proportion of embryos cleaving to at least the 5–8‐cell stage in the presence of α‐amanitin (32/52) was similar (P > 0.05) to that of controls cultured without α‐amanitin (25/50). In contrast, only 7.7% of α‐amanitin‐treated embryos cleaved to the 9–16‐cell stage, compared with 38.0% of the controls (P < 0.05), indicating that products of embryonic transcription were required for cleavage beyond the 5–8‐cell stage. In Experiment 2, embryos were cultured in the presence of 20 μM 3H‐uridine for 12 hr beginning at 24, 36, 48, or 60 hpi and subjected to autoradiography. Embryos of 5–8‐cell and 9–16‐cell stages (14 of 27 and 8 of 12, respectively) clearly demonstrated nuclear labeling, a finding also confirmed by computer‐aided densitometry. It is concluded that embryonic transcription and the MZT occur by the 5–8‐cell stage of IVM/IVF domestic cat embryo development and the MZT is not directly related to the partial morula‐to‐blastocyst developmental block observed in cultured IVF cat embryos. Mol. Reprod. Dev. 48:208–215, 1997. © 1997 Wiley‐Liss, Inc.