A study of some factors influencing fertility and sterility in the bull — Edition Insights

The Bull as Half the Herd

Gilman argues that the bull is “at least half the herd,” not only for genetic contribution but also for reproductive efficiency. He criticizes the common practice of judging fertility solely by a bull’s ability to copulate normally, noting that “gross changes in his genitalia, or the absence of spermatozoa from the semen are given due consideration, while other more obscure abnormalities are not looked for.” The thesis emphasizes that the bull can disseminate genital infections during copulation, making him a key vector in herd health. Gilman calls for systematic investigation of this role, which he says has been “discussed frequently” but not studied rigorously.

Observing Sperm Motility and Vitality

Gilman devotes considerable attention to the microscopic examination of semen, describing abnormal motion patterns such as “rotary swimming” and “pendulum swimming” as indicators of lowered vitality. He notes that freshly ejaculated sperm should exhibit “very active progressive movement” and that early transition to a slower, “undulatory tactile” type signals problems. The thesis also discusses the influence of vaginal secretions on sperm motility, citing cases where hostile mucus inhibits movement or, conversely, where vaginal fluids exaggerate activity. Gilman stresses that even a small percentage of motionless or low-vitality sperm reduces the chances of fertilization, given that many sperm are destroyed in the vagina and cervix.

Classifying Abnormalities and Infections

Gilman categorizes sperm abnormalities into structural changes and motility defects, and discusses conditions such as necrospermia (all sperm motionless) and aspermia (absence of sperm). He reports seeing only one case of aspermia, where the semen was “greatly increased in amount, and of a thin watery consistency.” The thesis also addresses genital infections, particularly cervicitis and vaginitis in cows, which can produce “acid and toxic vaginal secretion” that harms sperm. Gilman suggests that such infections may explain fertility problems in some herds, though he acknowledges the difficulty of proving causation. Throughout, he maintains a cautious, evidence-based tone, often noting when observations are “problematical” or require further study.

Gilman’s thesis is a reminder that early twentieth-century veterinary science was already grappling with the complexity of male fertility. Readers interested in the history of animal husbandry or the development of reproductive biology will find here a meticulous, if narrowly focused, precursor to modern andrology. The work is best approached as a primary source document, revealing both the state of knowledge in 1922 and the persistent challenges of diagnosing subfertility.