Submitted to: Canadian Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2013
Publication Date: 6/2/2013
Citation: Mason, M., Caudra, E.J., Elsasser, T.H., Lopez, J., Yoonsung, J. 2013. Evaluating the interaction between progesterone, TNF alpha and cortisol on early loss of transferred embryos in beef cows. Canadian Journal of Animal Science. 93:217-225. Interpretive Summary: The use of embryo transfer from one cow to another for specific breeding is a mainstay of the cattle industry. Still, the efficiency of breeding success as measured with the birth of a live calf remains lower than optimal because following conception not all embryos are retained by the mother’s uterus. Although the process of embryonic retention is regulated by many physiological and metabolic factors, attempts to manipulate the success of embryo transfer by altering blood concentrations of the natural pregnancy hormone progesterone has been the main focus of several studies designed to enhance embryo survival during early pregnancy. Nevertheless, supplementation of progesterone early during gestation to enhance embryo survival appears to be a controversial practice at present mainly due to the contradicting results reported in the literature. A significant part of this retention problem may reside in how the recipient cow’s immune system reacts to the presence of this foreign tissue embryo. The ability to maintain a pregnancy has been compared to an immune system slump that permits the temporary acceptance of a foreign or non-pure maternal tissue to grow in the uterus and the increased levels of progesterone facilitate this “immune slump”. The present study increased our understanding of the immunology of pregnancy and offered for the first time a reason for why some animals receiving embryos were not able to maintain them. The data clearly indicated that another locally produced immune hormone called tumor necrosis factor-alpha (TNF) played a critical role in maintaining pregnancy in embryo transfer cows. In reproductive tissues like the uterus and placenta, TNF stimulates the reorganization of cells that maintain the pregnancy. Cows that had low TNF levels following embryo transfer had poor pregnancy outcomes. The data suggest that TNF may be a biomarker useful to following pregnancy and indicating when management measures should be taken to help the cow through pregnancy.
Technical Abstract: 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 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 CIDR (Controlled Internal Drug Release) additionally inserted. Blood samples for progesterone, TNF-a and cortisol analysis were taken immediately before insertion and removal of CIDR’s and 7 days 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 days after insertion of the embryos in the control animals, compared to 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 to non-pregnant and correlated between day 0 and day 14. These results suggest that high levels of progesterone during the first 14 days after the transfer are indicative of the survival of transferred embryos. Additionally, this data also indicates 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.