Impact of Estrus Expression and Conceptus Presence on Plasma and Uterine Glucose Concentrations up until Maternal Recognition of Pregnancy in Beef Cattle.

Glucose is an essential component of uterine luminal fluid (ULF), it is a major energy source utilized by the conceptus for growth and development. Previously we reported increased concentrations of glucose in the ULF of cows that exhibited estrus, and observed differences in glucose transporter transcript abundance within the uterine endometrium. Our objective was to determine the relationship between plasma and uterine glucose concentrations throughout the estrous cycle and early stages of pregnancy. Beef cows/heifers were synchronized with the CO-Synch protocol and artificially inseminated (d0). Cows were classified by expression of estrus (estrus and no estrus). Blood was collected to determine glucose concentrations (d0, d5, d8, d10, d12, d16) using the Glucose Liquicolor assay. Uteri were flushed to collect d16 conceptuses nonsurgically (Rep 1; n = 29), or following slaughter (Rep 2; n = 37). Flush media was analyzed for glucose concentration. Data were analyzed using the MIXED procedure in SAS. There was an effect of replicate on glucose concentration (P < 0.006). There was no effect of time (P = 0.79) or conceptus (P = 0.16) on glucose concentration; however, there was a tendency for estrus cows to have lower glucose concentrations compared to no estrus cows (P = 0.06). There were no two-way interactions between time, conceptus, and estrus (P > 0.24). There was no correlation between uterine and plasma glucose concentrations in either replicate on d10, d12, and d16. In summary, there was no effect of time or conceptus on glucose concentration in beef cows, while estrus cows tended to have decreased glucose concentration. There was no correlation between uterine and plasma glucose concentration, therefore the increased uterine glucose concentration among estrus cows on d16 is most likely due to changes in specific glucose transporter expression in the uterine endometrium. USDA is an equal opportunity provider and employer.