|Unfortunately, not all
domestic animals breed as reliably as the proverbial rabbit. In some
cases, there may be a genetic component, and one largely the fault of
human selection over the generations for certain, "desireable" traits,
which may have ignored those for fertility. Species that are raised
primarily for commercial purposes, and often under relatively harsh,
rangeland conditions (sheep and cattle), have far fewer reproductive
problems of a genetic nature than do species which have been
domesticated for centuries, and which have a more companion oriented
place in society (horses and dogs). It is only natural that low
fertility of a genetic nature will be ruthlessly "weeded out", either by
the rancher's culling decisions, or by Nature herself. It is interesting
that despite tremendous advances in knowledge and treatment capability
over the past 450 years, foaling rates of horses (percentage of mares
bred that deliver a live foal the following year) have NOT CHANGED over
that period of time.
Of course individual animals may be afflicted with a variety of problems related to nutrition, extreme weather conditions, infection, or hormonal imbalance. These problems are usually treatable, particularly in the earlier stages, and represent most of our fertility diagnosis and treatment services (see Fertility Evaluation). All of our patients are given a daily vitamin-mineral supplement to insure that trace elements particularly crucial to reproductive processes, such as copper, cobalt, and zinc, are adequately present in the diet. Such supplementation can be particularly beneficial, it seems, when superovulating donor cows for embryo transfer, and in working with problem mares.
Uterine infections can sometimes be rather insidious; a normal, healthy uterine lining is very capable of rapidly eliminating bacterial challenge, but one which is not so healthy may only keep an infection "in check". Occasionally we find mares having a history of repeated negative uterine cultures, yet further investigation, including cytology and biopsy, clearly indicate that a "low-grade" infection is present; sometimes bacteria are even seen by the pathologist examining a biopsy specimen, and these are most often "hiding out" in the glandular crypts lining the uterine wall.
A general treatment approach is to thoroughly investigate the problem, determine the probable cause(s), institute and complete the best possible treatment approach, and then perform advisable procedures which will not only nurture the reproductive system back to full health as best possible, but maintain that condition.
Common fertility problems we encounter are heat-related decrease in semen quality in cattle and sheep causing poor pregnancy rates in summer and early-autumn; mares with poor conception rates, generally due to poor uterine condition (air and bacterial irritation are the most common causes); and dogs with poor conception rates related to poor timing of breeding.
Less common conditions have included permanent damage to sperm production and cessation of fertility due to suspected steroid administration in a stallion, infectious epididymitis in a bull which necessitated unilateral castration to preserve the other testicle (the remaining testis generally hypertrophies once his companion has disappeared; ultimately sperm production will be close to what it was originally with both of them present); male dogs with low libido (I guess 'guys' get headaches, too!); fungal uterine infections in mares; and a bull who produced normal quality semen, but who had been to multiple other freezing centers to produce frozen straws, without success. In this latter case, we developed a custom-extender which apparently had the right milieu of nutritional components for the sperm, and which resulted in straws of normal postthaw motility and fertility.
We always ask for as much history about the patient as possible; often earlier investigative work need not be repeated, or the absence of certain procedures may suggest a first course of action. Examination of the patient then leads to further findings and finally, a course of action based upon detailed knowledge. Fortunately, most of the problems we see are at least partially treatable, but we can never emphasize enough the importance of early examination.