X-chromosome monosomy in an infertile female llama.

A 3-year-old female llama was examined because of a history of infertility and apparent anovulation. The llama had indifferent behavior when penned with a male, but eventually would assume sternal recumbency for breeding. On examination, the llama was underweight and small in stature. The uterine horns and ovaries could not be identified during palpation or ultrasonography per rectum, and the cervix was dilated when examined with a speculum. Chromosomal preparations of lymphocytes and skin fibroblasts were performed; all cells examined had a 73, X karyotype (X-chromosome monosomy). To our knowledge, this is the first report of a chromosomal anomaly in a llama. Signs seen in this llama were similar to those seen in mares with X-chromosome monosomy. This condition should be considered in the differential diagnosis of infertility in llamas that fail to ovulate, especially if other abnormalities such as indifferent sexual behavior and short stature are present.