Abstract #LB1

# LB1
Fertility may depend on conceptus-derived signals in lactating dairy cows.
Bethany E. Liebig*1, Milton G. Thomas2, Kevin D. McSweeney3, Hana Van Campen1, Jeanette Bishop1, Thomas R. Hansen1, 1Department of Biomedical Sciences, Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins, CO, 2Department of Animal Sciences, Colorado State University, Fort Collins, CO, 3Department of Clinical Sciences, Colorado State University, Fort Collins, CO.

Infertility and early embryonic mortality (EM) negatively affects cattle industries. Most fertility traits such as daughter pregnancy rate (DPR) and services per conception (SPC) are lowly heritable (h2 ≤ 0.10). Interferon tau (IFNT) is a cytokine released by the conceptus during trophoblast elongation and differentiation that decreases prostaglandin F (PGF) release from the endometrium and prevents lysis of the corpus luteum (CL), thus maintaining production of progesterone. Embryo survival depends on robust IFNT release and action through inducing IFN stimulated genes (ISGs). We hypothesized that DPR and SPC could be used to select for viable embryos with greater IFNT production. Freshening dairy cows (n = 86) were sorted by genome-enhanced predicted transmitting ability (gPTA-DPR; Clarifide; Zoetis) and SPC into low fertile (LF; −2.3 gPTA-DPR; 3.7 SPC) and high fertile (HF; −1.3 gPTA-DPR; 1.4 SPC) groups. Cows were assigned to HF nonpregnant (NP), LF pregnant (LP) or HF pregnant (HP) groups (n = 7 each). Cows were estrous synchronized and time-artificially inseminated to a HF bull (+1.8 DPR). Sixteen days later, embryos were collected and typed as viable or EM based on morphology and length. Data were analyzed using protected (P < 0.05) t-test. There were no differences in serum progesterone concentrations (using ELISA), days in milk, number of lactations or calving date between groups. The gPTA-DPR was negatively correlated (r = −0.52; P < 0.05) with SPC. The HP cows had more viable (n = 5) embryos based on morphology than the LP cows (n = 3). Viable HP embryos were longer (P < 0.05) than LP embryos. Uterine flushing (UF) IFNT concentrations (using Western blot) were greater (P < 0.05) in HP compared with LP cows. Concentrations of IFNT in UF from viable embryos were positively correlated with gPTA-DPR (r = 0.57, P < 0.05) and explained ~46% (R2 = 0.46) of the variation in gPTA-DPR. Peripheral blood mononuclear cell ISG15 mRNA concentrations (using RTqPCR) were upregulated (P < 0.05) in HP compared with LP cows. In conclusion, selection of dairy cows combining gPTA-DPR and SPC may improve fertility through increased production and action of IFNT. Funded by Zoetis Inc.