Biochemical changes in blood and allantoic fluid during late pregnancy of cloned embryos in Nellore cows.

During pregnancy, changes in the uterus-placenta-fetus complex are modulated by the presence of the conceptus and may determine pregnancy success. Many pathological changes in the uterus-placenta-fetus complex throughout the pregnancy of bovine embryos cloned by somatic cell nuclear transfer (SCNT) have been described. We hypothesized that maternal blood and allantoic-fluid biochemical profiles would differ during late gestation according to pregnancy origin (artificial insemination or SCNT) and subsequent outcome (live birth or pregnancy loss). Twenty-two healthy multiparous pregnant Nellore cows were used for blood and allantoic fluid collection every fortnight starting at 150 days of gestation until natural birth or abortion. Data were normalized to birth or abortion (day 0), and the three preceding fortnights were analyzed. A comprehensive description of reference values for various biochemical and blood gas parameters using serum and total blood samples, and a few blood gas parameters in allantoic fluid of naturally-produced (control; n = 6) and SCNT clone (clone; n = 16) pregnancies in Nellore cows is the most important result of this study. Serum cholesterol was higher in SCNT than control pregnancies; however, no diagnostic threshold or predictive-performance measure was evaluated. The central hypothesis of this study in which gestational changes in the uterus-placenta-fetus complex can be differentially detected earlier by biochemical and hemogasometric analyzes in maternal blood and/or in the allantois fluid of SCNT and control pregnancies was partially supported. Potassium, phosphorus, calcium, glucose, and urea levels differed between AI- and SCNT-derived pregnancies, indicating distinct gestational metabolism. Only cholesterol was higher in SCNT than control pregnancies and showed different temporal trajectories among outcome subgroups. Its metabolism could be related to abortion in SCNT pregnancies, but more investigations should be done.