Associate Professor Graduate Program Director 206 Brehm (865) 974-7286 Fax: (865) 946-1010 Email: jedwards@utk.edu Research Appointment: 85% Teaching Appointment: 15%
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ELUCIDATE MECHANISMS THROUGH WHICH ENVIRONMENTAL HEAT STRESS REDUCES FERTILITY IN DAIRY COWS. Infertility in beef and dairy cattle may be as high as 30-40%. In other words, out of 100 cows, 30 to 40 cows on average will not produce a calf after insemination. Impose environmental heat stress, as occurs during hot humid summers in the Southeast, and infertility may be as high as 70-100%. Heat-induced infertility is one of the most important economic challenges facing the dairy industry. This is, in large part, because pregnancy is requisite for lactation (i.e., no pregnancy, no milk, no money for the dairy producer). During the past five years, Dr. Edwards’ laboratory has made great strides towards determining why heat-stressed dairy cows do not get pregnant and most importantly have generated data suggestive of potential strategies to mitigate negative effects of heat stress to reduce fertility. In particular, her laboratory has identified developmental stages that the egg is susceptible to direct effects of elevated body temperatures in heat-stressed dairy cows. Second, they have identified specific components within the egg that are altered by physiological relevant elevated temperatures. Repeated experimentation has shown damaging effects to be temperature and duration dependent suggesting that regardless of the specific component of the egg that is altered, effects of heat stress to reduce continued development of the egg after fertilization are not necessarily irreparable. This research focuses on specific priority areas outlined by the USDA by addressing the ever-growing problem with infertility in dairy cows. It does so by investigating the basic mechanisms regulating fertility and explores one potential strategy to ameliorate the effects of heat stress to increase infertility in dairy cows. Dr. Edwards’ research towards this focus area is funded by the National Research Initiative Competitive Grant No. 2004-35203-14772, from the USDA Cooperative State Research, Education, and Extension Service, USDA Initiative for Future Agricultural and Food Systems Program (Grant No. 2001-52101-11318), USDA Hatch Funds and the State of Tennessee through the Tennessee Agricultural Experiment Station and the Department of Animal Science (for participation in the S-299 Regional Heat Stress Project), and USDA-NRI (Grant No. 1999-03637).

IDENTIFYING GENES OF ECONOMIC IMPORTANCE TO THE DAIRY INDUSTRY: The choice of an egg as a starting material to unravel some of the mysteries of infertility is logical as it contributes half of the genetic material and greater than 99% of the cytoplasm to the early embryo. Of particular interest to Dr. Edwards’ laboratory are the pools of maternal transcripts within the egg cytoplasm that needed for continued development as they provide the necessary templates for protein synthesis during critical time periods when the egg and early cleavage stage embryo are incapable of transcribing their own. Although the importance of maternal pools of mRNA for continued development is largely known, the specific transcripts (genes products) contained within the large pool of mRNA that play an important in development, remain largely unknown. In an effort to identify these important transcripts, Dr. Edwards’ laboratory, in collaboration with Dr. Neal Stewart, is using microarray analysis to profile the transcripts of developmentally competent versus incompetent oocytes. Doing so is an important step towards identifying genes of economic importance to the dairy industry related to improving fertility.

With the expectation that cloned offspring would be an important byproduct of her developmental research investigating the importance of maternal cytoplasm versus nuclear components of the oocyte for embryo development, Dr. Edwards teamed with Drs. Neal Schrick and Steve Oliver, co-director of the UT Food Safety Center of Excellence. The basis of their collaboration was to ensure that resulting offspring would be useful for addressing other important aspects of animal agriculture. In particular, somatic cells from Jersey cows previously confirmed susceptible or resistant to mastitis were used for developmental studies. Doing so, effectively provided collaborators with a unique set of genetically identical Jersey cows to be used in subsequent studies to determine the factor(s)/genes responsible for mastitis disease resistance/susceptibility. Mastitis is an inflammation of the udder affecting a high proportion of dairy cows throughout the world. It is a disease that has been described as the most economically-imposing on dairy producers in the United States, costing an estimated $2 billion annually. To date, great strides have been made towards this collaborative effort. In total, 12 clones of two Jersey cows were produced and have been reared in a production environment. This research has been supported in part by the The UT Food Safety Center of Excellence and USDA Hatch Funds and the State of Tennessee through the Tennessee Agricultural Experiment Station and the Department of Animal Science. Information regarding this focus area is available via the web at ( http://animalscience.ag.utk.edu/utcloneproject/default.html).