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

Breeding soundness examination of stallions includes the examination of rep roductive organs, behavior, quantity and quality of the ejaculate and funct ion of the reproductive endocrine system. The paper reviews the current kno wledge of this field. First, the morphology of the equine spermatozoa is de scribed in details. Semen examination is divided into routine and advanced laboratory procedures and new techniques. During routine laboratory examina tion, 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, d ata on morphology from different Laboratories are difficult to compare. Fol lowing routine laboratory tests, morphological and functional membrane inte grity and acrosome integrity can be determined. Several non fluorescent and fluorescent staining techniques have been developed to determine the viabi lity and/or the acrosomal status of spermatozoa which can be used separatel y or in combination. Hypo-osmotic swelling (HOS) test is a relatively simpl e test to evaluate the functional integrity of the spermatozoal membrane. N ew automated techniques, such as computer assisted sperm analysis (CASA) an d flow cytometry have been developed recently. These new methods allow us t o evaluate different motility parameters, morphology, different compartment s and functions of individual cells, including the nucleus, plasma membrane , mitochondria, capacitation, acrosomal status. The determination of baseli ne concentration of reproductive hormones helps to evaluate the breeding so undness of stallions. GnRH and hCG challenge-tests are also available to mo nitor 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.