Effect of High Urea and Low PH on Uterine Response to Interferon Tau
Reproductive performance of dairy cattle, an important contributor to profitability, has declined steadily over the last few decades. To increase milk yield and profitability, dairy farmers commonly feed diets that contain high levels of protein. However, feeding high dietary protein results in elevated urea and acidic pH in the uterus, which can be detrimental to fertility. Elevated urea concentration and reduced uterine pH, may alter uterine secretions and affect fertility by impairing sperm, ova, or the early embryo. During maternal recognition of pregnancy, the uterine endometrium responds to the embryonic signal interferon-tau (IFN tau), and becomes highly secretory, producing a variety of proteins (histotroph), which are essential for embryo survival and attachment. In cattle, uterine glands secrete proteins including ISG15 and Mx1 in
response to IFN tau. Because these two proteins are upregulated during early pregnancy and they are IFN tau-stimulated proteins; they may be critical to the function and establishment of the uterine microenvironment during early pregnancy. The effect of high concentrations of urea and acidic pH on secretion of the uterine epithelium is unknown. If high urea concentrations and (or) low pH affect the uterine environment, it is possible that uterine gland secretion may be reduced or abrogated, even in the presence of IFN tau. Therefore, alteration in the uterine environment and interruption of communication between the embryo and the dam, may explain in part, the associations between high dietary protein and decreased fertility in dairy cows. A long term goal of our research is to elucidate the mechanism by which high dietary protein intake affects dairy cow fertility, specifically through
the investigation of the interaction of the conceptus and the uterine environment. The specific aims of this seed grant proposal is to examine the effect of urea, pH, and high dietary protein on IFN tau-induced protein expression in bovine endometrial cells and the uterus of lactating cows. The findings will be presented in the regional and national scientific meetings. The proposed experiments will provide the foundation for future investigations into the role of urea and pH in uterine secretion, specifically aimed at achieving our long term goals, i.e., to 1) elucidate the mechanism by which high dietary protein affects the interaction of the conceptus and the uterine environment, and 2) improve the reproductive efficiency of dairy cattle through the greater understanding of the interaction between nutrition and reproduction. Impact: Conception rates have been reported to be decreased
in cows with high blood urea. With growing evidence that dairy profitability increases as pregnancy rate (PR) increases, it is financially important to the US dairy industry to further investigate the effect of high dietary protein intake and fertility. Adjusting the dietary protein and lowering the level of BUN, especially during breeding and early embryo development, might improve PR in dairy cattle. Each 1% increase in PR results in the return of approximately $US 12 to 15 per cow per year regardless of herd size.