Mason, M., Cuadra, E. J., Elsasser, T. H., Lopez, J. and Yoonsung, J. 2013. Evaluating the interaction between progesterone, tumor necrosis factor-alpha and cortisol on early loss of transferred embryo in beef cows. Can. J. Anim. Sci. 93: 217-225. Fifty-eight non-lactating cows previously synchronized for estrus were assigned to two treatments to assess the effects of progesterone supplementation and its correlation with tumor necrosis factor-a (TNF-a) and cortisol on the survival of the transferred embryos. On day 7 after exhibiting estrus (day 0), cows in both groups received embryos. In contrast with the control group, animals in the CIDR-group had a controlled internal drug release (CIDR) additionally inserted. Blood samples for progesterone, TNF-a and cortisol analysis were taken immediately before insertion and removal of CIDRs and 7 d after insertion. Progesterone did not differ between the control and the CIDR animals at any day of the study; however, it significantly increased at 7 and 14 d after insertion of the embryos in the control animals, compared with the levels observed in that same experimental group at the time of the transfer. Regardless of the treatment, all pregnant cows experienced a significant increase in progesterone from day 0 to day 7. Progesterone on day 0 was correlated to itself (r=0.46) on day 14 and to TNF-a (r=-0.37) on day 0 in pregnant animals; TNF-a on day 7 was significantly higher in pregnant cows compared with non-pregnant and correlated between day 0 and day 14. These results suggest that high levels of progesterone during the first 14 d after the transfer are indicative of the survival of transferred embryos. Additionally, these data also indicate that the decrease in TNF-a concentration on day 7 after the transfer of embryos may be associated with the low concentrations of progesterone observed in the non-pregnant animals.