Assessment and prediction of embryo survival in fertility-classified beef cows.

Pregnancy after embryo transfer (P/ET) in synchronized beef cows that show estrus is usually less than 50 %. Fertility is associated with the ability of the uterus to sustain embryo development, interferon-tau (IFNT) signaling and placentation. The hypothesis is that expression of functional markers of interferon signaling and placentation increases according to cow fertility. Cyclic, Bos indicus-influenced, primiparous cows (n = 50) were submitted to ET 7 days after estrus (D7). Pregnancy diagnosis was conducted on D20, D32, D39 and D46. Blood was collected on D20 to quantify expression of interferon-stimulated gene 15 (ISG15) from peripheral blood mononuclear cells (PBMC) and on D25, D32, and D39 to quantify the abundance of pregnancy associated glycoproteins (PAGs). Pregnancies were terminated on D46. After a 35-day recovery period, the same animals were enrolled in a new round of ET, for eight subsequent rounds. Estrus expression was 72.3 %. P/ET was 82.3, 64.3, 61,6 and 59.5 % on D20, D32, D39 and D46, respectively. There was no effect of round, season (warm vs. cold) or year (1 vs. 2) on P/ET. Based on D46 P/ET, cows were classified as Fertile (FERT; n = 7), Moderately fertile (MF; n = 24) or Subfertile (SF; n = 17). Expression of ISG15 was 71.4 % greater in Fert vs. SF cows. Serum concentrations of PAGs increased over time regardless of fertility classification. In conclusion, responsiveness to IFNT was reduced in SF cows. Placental function based on PAG concentrations was similar among fertility classifications. The identification of FERT and SF cows can profoundly impact the cow-calf sector of the beef industry.