Methods for semen and endocrinological evaluation of the stallion:: A review

Breeding soundness examination of stallions includes the examination of reproductive organs, behavior, quantity and quality of the ejaculate and function of the reproductive endocrine system. The paper reviews the current knowledge of this field. First, the morphology of the equine spermatozoa is described in details. Semen examination is divided into routine and advanced laboratory procedures and new techniques. During routine laboratory examination, the quantitative (volume. concentration, total sperm number) and the qualitative (appearance, motility, morphology) parameters of the ejaculate are determined. Owing to different evaluation systems and interpretation, data on morphology from different Laboratories are difficult to compare. Following routine laboratory tests, morphological and functional membrane integrity and acrosome integrity can be determined. Several non fluorescent and fluorescent staining techniques have been developed to determine the viability and/or the acrosomal status of spermatozoa which can be used separately or in combination. Hypo-osmotic swelling (HOS) test is a relatively simple test to evaluate the functional integrity of the spermatozoal membrane. New automated techniques, such as computer assisted sperm analysis (CASA) and flow cytometry have been developed recently. These new methods allow us to evaluate different motility parameters, morphology, different compartments and functions of individual cells, including the nucleus, plasma membrane, mitochondria, capacitation, acrosomal status. The determination of baseline concentration of reproductive hormones helps to evaluate the breeding soundness of stallions. GnRH and hCG challenge-tests are also available to monitor the function of the hypothalamus-pituitary-testis axis. The accuracy of all these methods has to be confirmed on a large number of stallions and their correlation with fertility has to be determined. The content of the paper is the following: 1. Introduction 2. The equine spermatozoon Plasma membrane Head Tail 3. Semen examination 3.1. Routine laboratory tests 3.1.1. Quantitative parameters Volume Concentration Total sperm number 3.1.2. Qualitative parameters Appearance Motility Morphology 3.2 Advanced laboratory tests: evaluation of membrane integrity Morphological integrity: viability Functional integrity: hypo-osmotic swelling Acrosome integrity 3.3New techniques Mitochondrial activity Capacitation of spermatozoa and calcium influx Binding activity Morphometric analysis Chromatin analysis 4. Diagnostic endocrinology in stallions GnRH challenge HCG challenge 5. References.