Early Embryonic Loss in Dairy Cattle and the Search for Hormonal Therapy or Other Management Measures to Improve It

The most recent issue of the Journal of Dairy Science has several papers regarding decreased fertility in dairy cattle, and the efforts to develop hormonal treatment regimens to improve fertility. Much of the recent work focuses on trying to reduce loss of fetuses during early pregnancy. This prompted me to search the literature about this extensive and important subject area. I suspect that Utah is at least as much affected as are other parts of the country by the phenomenon that particularly during the hot summer, dairy producers find getting and keeping cows pregnant a constant challenge, if not outright frustrating. There are numerous papers with data showing that during approximately the last 30 years, since the mid1970’s, all measures of dairy cattle fertility including time to first service, services/conception, maintenance of early pregnancy, percentage pregnant by a certain time such as 150 DIM, and days open (this number includes only pregnant cows and should never be the sole way to monitor reproductive performance in a herd) are worsening in Holsteins and Jerseys. As dairy cows have been selected and fed for higher dry matter intake and milk production, there has been an associated decrease in circulating progesterone concentration in the cows. A paper by JS Stevenson et al., Journal of Dairy Science, July 2008 explains that serum progesterone concentration before AI is positively correlated with conception rate; progesterone concentrations greater than 5 ng/ml have been associated with conception rates improving from approximately 45% in cows below that level to approximately 65%. The article also mentions that previous studies, including some by R. Sartori et al., have found that as dairy cattle age, their ovulatory follicles and ovarian structures become larger than in heifers, but serum progesterone levels are lower than would be expected based upon CL size.