Lack of natural luteolysis associated with uterine horn aplasia in a heifer.

A heifer with congenital left uterine horn aplasia had completely normal reproductive cycles when ovulation occurred from the right ovary. Subsequent to ovulation from the left ovary, however, the corpus luteum persisted for months unless prostaglandin F2 alpha was administered. The reproductive tract was examined after slaughter. The left oviduct ended blindly, resulting in fluid-filled cysts. Except for aplasia of the left uterine horn, the reproductive tract appeared to be morphologically normal. This natural model confirms that the luteolytic signal in cattle is sent from the uterine horn to the ipsilateral ovary, but not to the contralateral ovary. Diagnosis of this abnormality required careful palpation per rectum. The normal luteolysis that occurred with exogenous prostaglandin F2 alpha treatment provided misleading information that the heifer was normal.