Stallion Clinical Endocrinology: What Do We Really Know?
Sue M McDonnell
Equine Behavior Lab, Section of Medicine and Reproduction
University of Pennsylvania School of Veterinary Medicine
Kennett Square, Pennsylvania USA

            Assays for a variety of stallion reproductive and metabolic hormones are available from several university or commercial endocrine laboratories, either as single hormone tests or as sets of hormone tests bundled as ”stallion profiles” or “stallion panels.”   Laboratory recommendations vary for sampling protocols and sample handling methods.  At present there do not appear to be well accepted or well understood guidelines for interpretation. Accordingly, many questions arise concerning the reliability and usefulness of endocrine studies in stallion practice.  The objectives of this work session are to:

1)                 critically discuss the current use of various endocrine assays and studies of peripheral serum or plasma and/or testicular biopsy samples in routine breeding soundness exam and/or subfertility evaluations of stallions

2)                 explore research needed to improve or expand the usefulness of endocrinology to stallion practice.  

Perhaps we can organize our discussion around the following simple related questions. 

·        What fertility problems can be ruled out with currently available and practiced endocrine evaluation?

·        Do we know of any reproductive pathology in the stallion for which endocrinology is a critical diagnostic tool?

·        Are there any clinical conditions in stallions in which serious reproductive endocrine aberrations exist that are not evident by examination of the testicle and or semen?

·        In stallion practice, it is ever the case that a fertile, normal stallion is found to have serious aberrations in hormone profile?

·        For which hormones and sampling protocols do we have adequate norms for clinical comparison?

·        Which hormone assays are practically available at this time?

·        What hormone assays are being used?

-routine breeding soundness examination

-high stakes pre-purchase breeding soundness examination

-routine monitoring of breeding stallions

-semen-related subfertility examination

-behavior-related subfertility evaluation

·        Do we know enough about how field variation in sampling schedules, handling, and shipping affect results?

Acknowledgements

                Dickson Varner specifically requested that we devote time at this workshop to clinical endocrinology.  Dickson kindly provided an unpublished manuscript coauthored by Terry Blanchard detailing some of their current thinking on the use of hormone analyses in the clinical evaluation of stallions. Dickson, as well as Charley Love and Janet Roser kindly agreed to assist as active discussants for this work session.