Use of interferon-tau stimulated genes and bovine pregnancy-associated glycoproteins to predict pregnancy loss in Nelore cows and heifers

Abstract

Reduction in postpartum and conception intervals are necessary to increase productivity and profit of cattle herds, and embryonic mortality is one of the major causes for this period prolongation. Pregnancy losses can result in low pregnancy rates, delay in genetic gains and substantial financial losses for milk and beef production. Therefore, to allow females new chances of conceiving in a shorter interval of time, it is necessary to identify embryonic mortality as early as possible to positively impact the profitability of livestock production systems. In the present study, we hypothesized that bovine conceptus can stimulate transcripts in immune cells and pregnancy associated glycoproteins that could serve as biomarkers of early gestation and predictors of embryonic vitality. Thus, the main objective of this study is to evaluate the expression of interferon tau-stimulated genes (ISGs) in peripheral blood polymorphonuclear cells (PMNs) and pregnancy associated glycoproteins (PAG) concentrations on the third and fourth week after fixed time artificial insemination as markers of pregnancy and embryo loss in Nelore heifers and cows. For this, females will have estrous cycle synchronized, and after fixed time artificial insemination (D0), blood samples will be collected for analysis of expression of ISGs by RT-qPCR on day 20, and analysis of PAG concentrations by ELISA on day 24. Pregnancy diagnosis will be performed on D20 by Doppler ultrasonography, and on days 30, 60 and 90 by B-mode ultrasonography through the detection of embryonic vesicle. On days 20, 24, 30 and 60 blood samples will also be collected for analysis of progesterone concentrations. After final pregnancy diagnosis (D60), females will be divided in four groups: pregnant, non-pregnant, early pregnancy loss (Days 20-30) and late pregnancy loss (Days 30-60). ISGs expression profile and PAG concentrations will be compared between the groups. It is expected that both techniques will be efficient in early identification of pregnancy and embryonic losses, aiming their application in research, management of commercial herds and progress of animal production. (AU)