A 1939 article in the "Journal of Heredity" describes two offspring of a fertile mare mule named "Old Bec", which was owned at the time by Texas A&M University in the late 1920s. One of the foals was a female, sired by a jack. Unlike her mother, she was sterile. The other, sired by a five-gaited Saddlebred stallion, exhibited no characteristics of any donkey. That horse, a stallion, was bred to several mares, which gave birth to live foals that showed no characteristics of the donkey.