Blood chemistry, nutrient metabolism, and organ weights in fetal and newborn calves derived from in vitro-produced bovine embryos

Calves born after in vitro production (IVP) of embryos often show reduced p erinatal viability. The present experiment investigated a series of physiol ogical variables in the immediate prenatal and postnatal period of IVP dair y calves. Petal IVP and control calves (each n = 7) were prepared with vasc ular catheters at 248 +/- 1 day gestation (term = 280 days), and blood samp les were taken for five days before premature delivery by cesarean section. IVP fetuses compared with controls had significantly elevated arterial hem oglobin and oxygen content (8.41 vs. 7.52% and 5.75 vs. 3.79%, respectively ) whereas lactate level was lowered (1.89 vs. 2.26 mM). The umbilical venou s-arterial concentration differences in oxygen, lactate, and glucose indica ted that IVP fetuses relied more on lactate and less on glucose as oxidativ e substrates. The fetal glucose tolerance, and the basal and adrenocorticot ropin-stimulated cortisol levels were similar between the groups. In the im mediate postnatal period, IVP calves showed elevated venous blood pH (7.294 vs. 7.270), hemoglobin (9.06 vs. 8.25%), oxygen contents (6.33 vs. 4.64%), KC levels (4.89 vs. 4.56 mM), and rectal temperature (38.9 vs. 37.4 degree s C), and lowered blood Na+ (139.9 vs. 141.0 mM), CI- (100.2 vs. 103.1 mM) and glucose levels (2.86 vs. 3.11 mM). There were no differences in body di mensions and organ weights, except that the fore legs and hind legs were sl ightly longer in the IVP group (76.1 vs. 72.4 cm and 93.4 vs. 88.8 cm, resp ectively). Although prenatal and neonatal IVP calves differed from control calves in a number of variables, the effects were relatively minor and prov ide no direct evidence for the hypothesis that IVP calves have an impaired capacity to adapt to life ex utero. In fact, several parameters indicated e nhanced rather than retarded maturation of IVP calves when data from premat ure calves were compared with data from a group of control carves delivered at term.