104 Metabolic, electrolyte and acid-base parameters in blood and fluids of the reproductive tracts during in vivo maturation of bovine oocytes.

Abstract Follicular fluid is the microenvironment that supports oocyte maturation and competence. Using Abbott iSTAT1™ and NanoDrop, we determined the dynamics of acid-base, electrolyte, metabolites, and total protein in venous blood, fluids of the dominant follicle (FF), oviduct (OF), and uterus (UF) during the window of oocyte maturation. Holstein heifers (n=36) were synchronized with PGF2α on Days -11 and 0, CIDR during Days -6 to 1, and GnRH given on Day 2 after 2nd PG. Samples were collected at 24h, 48h, 60h, 72h, and 78h after 2nd PG. Most electrolytes analyzed, Cl-, K+, and Ca2+ were significantly affected in blood and FF (P<0.05) by CIDR removal. Similarly, Cl- and Na+ also significantly changed in OF and UF across time. Glucose, lactate, and creatinine significantly changed across time points in FF compared to blood. Moreover, pO2, pCO2, TCO2, and pH significantly changed across time in FF. Most parameters were not significantly correlated between blood and FF across time points except for glucose, Cl- and creatinine. Furthermore, pO2 in FF was nearly 3X higher than blood, suggesting low O2 during in vitro maturation is inappropriate. In conclusion, components of the follicular fluid undergo major changes during the window of oocyte maturation.