There are great differences in the developmental competence of oocytes collected from individual cows. Oocytes grow and mature in the follicular fluid (FF). In the present study, characteristics of the FF of each ovary and the developmental competence of enclosed oocytes were investigated, and these data were then compared. A total of 37 pairs of ovaries were collected from beef heifers. The concentration of magnesium (Mg), aspirate aminotransferase (AST), nonesterified fatty acids (NEFA), and lactate dehydrogenase (LDH) in the FF were great compared with serum standard. Several significant correlations among these characteristics were detected. Forty-eight hours after fertilization, the stage of embryo development at an advanced developmental stage (>6 cell stage) is related to the rate of blastulation 8 days after fertilization. In addition, a significantly positive or negative correlation was observed between the developmental competence (the rate of cleavage in the embryo and blastulation) and the concentration of the icterus index (ICT) or blood urea nitrogen (BUN) in the FF. In conclusion, the quality of oocytes is affected by the environment in the follicle, and BUN or ICT is a predictable index of the developmental competence of oocytes. (c) 2005 Elsevier B.V. All rights reserved.