Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2006
Publication Date: 8/1/2006
Citation: Echternkamp, S.E., Vonnahme, K.A., Green, J.A., Ford, S.P. 2006. Increased vascular endothelial growth factor and pregnancy-associated glycoproteins, but not insulin-like growth factor-I, in maternal blood of cows gestating twin fetuses. Journal of Animal Science. 84(8):2057-2064. Interpretive Summary: Cows gestating twin fetuses have increased pre-calving nutrient and management requirements and enhanced placental function. The experimental objective was to assess the application of measuring vascular endothelial growth factor (VEGF), pregnancy-associated glycoproteins (PAG), and/or progesterone in the maternal blood during gestation to diagnose the number of fetuses in utero and to assess placental vascularity and function. Blood concentrations of both VEGF and progesterone were greater (P < 0.05) in dams with twins versus singles, but concentration differences were too small and variable to provide a valid diagnosis of fetal number in utero. In contrast, PAG was only detectable in the blood of pregnant cows, and PAG concentrations did not differ between cows gestating twin versus singleton fetuses at 56.6 and 121.2 days (range = +/- 10 d) post-breeding. However, PAG concentrations were significantly increased at 191.6, and 233.6 days (range = +/- 10 d) post-breeding and the increase was greater (P < 0.01) in cows gestating twins. Conversely, PAG concentrations decreased before and were nondetectable after abortion in the two cows that aborted. Although PAG concentrations were too variable to provide a valid diagnosis of fetal number in utero, preliminary results indicate the application of PAG measurements for early diagnosis of pregnancy (i.e., 25-35 days post-breeding) and for assessment of placental function in cattle.
Technical Abstract: Differences in placental mass and vascularity exist between cows gestating single versus multiple fetuses. Therefore, the association between fetal number and placental development and function were assessed by comparing concentrations of vascular endothelial growth factor (VEGF), pregnancy-associated glycoproteins (PAG), and progesterone in the maternal blood of MARC Twinner cows gestating one (n = 23) versus two (n = 17) fetuses. Samples of jugular vein blood were collected serially at 56.6, 121.2, 191.6, and 233.6 d (range = =/- 10 d) post-breeding (collection times 1, 2, 3, and 4, respectively). Plasma concentrations of VEGF and of progesterone were measured by double-antibody RIAs and of PAG by an indirect sandwich ELISA. Concentrations of VEGF and progesterone were greater (P < 0.05) in dams with twins versus singles. Conversely, PAG concentrations were low at times 1 and 2 and did not differ between singles and twins. The subsequent increase (P < 0.01) in PAG was greater in dams with twins, resulting in greater (P < 0.01) PAG concentrations with twins at times 3 and 4 (type of birth x time; P < 0.01). It is postulated that the greater PAG and VEGF concentrations in the blood of cows gestating twins are the result of a larger uteroplacental mass, including increased numbers of binucleate cells, and increased angiogenesis and vasculogenesis associated with a twin pregnancy. Although PAGs and VEGF were elevated in cows gestating twins, variability within and among birth groups limit the use of PAG or VEGF measurements for the diagnosis of twins.