Uterine and ovarian blood flow in a Holstein Friesian cow with aplasia of one uterine horn

The ovarian dynamics and uterine and ovarian blood flows of a 6-year-old (2 parturitions) Holstein Friesian cow with right uterine horn aplasia were observed during two estrous cycles. In one estrous cycle, a corpus luteum (CL) formed in the right ovary, but regression of the CL and subsequent ovulation were not observed. In the other estrous cycle, a CL formed in the left ovary and delayed regression of the CL and subsequent ovulation were observed. The blood velocity of the right uterine artery was lower than that of the left uterine artery throughout both estrous cycles when a CL formed in either the right and left ovary. The blood velocities of the right and left ovarian arteries were unaffected by right uterine horn aplasia and changed depending on the presence of a CL. These results indicated that the blood flow of the right uterine artery was very weak and that aplasia of one uterine horn affects the estrous cycle, especially CL regression.