**Endometritis and Infertility in the Mare – The Challenge in Equine Breeding Industry–A Review**

Maria Pia Pasolini, Chiara Del Prete, Silvia Fabbri and Luigi Auletta

Additional information is available at the end of the chapter

http://dx.doi.org/10. 5772/62461

#### **Abstract**

Most major infertility problems are complex and several factors can cause failure to pro‐ duce offspring. In the last few years, much of the efforts of practitioners and researchers working in equine breeding industry have been directed to individuate the pathophysio‐ logical mechanisms underlying poor reproductive performances in mares. Endometritis is on the talk in much of the recent research as the most frequent cause of subfertility in mares that cycle normally but do not conceive and in mares that cycle normally and con‐ ceive but then suffer early embryonic death. Post-breeding persistent endometritis, bacte‐ rial and other infective endometritis and poor uterine clearance have all been discussed in an attempt to define risk factors and a diagnostic algorithm. The aim of this chapter is to perform a thorough review of recent literature about endometritis. The diagnostic al‐ gorithms are carefully examined, highlighting pros as well as pitfalls of each diagnostic aid. Suggested therapeutic protocols are examined in the effort to detect what is actually recommended and what would better benefit from further corroboration. The idea that a better etiopathogenetical understanding of the endometritis remains the key to access to a correct diagnostic protocol and to a successful therapeutic plan will inspire this chapter.

**Keywords:** Endometritis, Mare, Diagnosis, Ultrasound, Therapy

### **1. Introduction**

Every year many mares fail to become pregnant. These failures represent a substantial economic and genetic loss to the horse industry. Most major infertility problems are complex and several factors, singly or in combination, can cause failure to produce offspring. In the last few years, much of the efforts of practitioners and researchers working in equine breeding industry have been directed to individuate the pathophysiological mechanisms underlying poor reproductive performances in mares. To clarify, infertility includes three "problems"

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mares' types: mares that fail to cycle, mares that cycle normally but do not conceive and mares that cycle normally and conceive but then suffer early embryonic death. Endometritis is on the talk in much of the recent research as the most frequent cause of the last two conditions.

Post-breeding persistent endometritis, bacterial and other infective endometritis and poor uterine clearance have all been discussed in an attempt to define risk factors and a diagnostic algorithm, essential to reach a definitive diagnosis and to apply the appropriate therapeutic protocol. Breeding-induced endometritis is a normal physiological reaction in the horse, as it is believed that an inflammatory response is necessary for the effective removal of contami‐ nating bacteria and excess spermatozoa introduced into the uterus. In a healthy uterus, the inflammation subsides within 48 hours, but the susceptible mares are not capable of resolving the inflammation triggered by sperm and develop persistent mating-induced endometritis (PMIE). A very strong relationship establishes between PMIE and infectious endometritis and a complex of mare (such as age, perineal conformation, uterine clearance and cervical compe‐ tence) and microbial (such as induction of inflammation, epithelial adherence, resistance to phagocytosis and viscosity of secretion) factors contribute to the pathogenesis of endometritis. Traditionally, the mares that are prone to endometritis are called susceptible, in contrast to the "resistant" ones, not prone to uterine infection.

The aim of this chapter is to perform a thorough review of recent literature about endometritis. The cascades of inflammatory signals being complex and intertwined, the etiopathogenetical, diagnostic and prognostic roles of the recently studied inflammatory markers are discussed. In addition, the most common bacterial and fungal pathogens involved are reviewed, together with the recent advances in diagnostic procedures. In fact, the diagnostic algorithms are carefully examined, highlighting pros as well as pitfalls of each diagnostic aid. Suggested therapeutic protocols are examined in the effort to detect what is actually recommended and what would better benefit from further corroboration, with special attention to the correct use of antimicrobials and antibiotics, their common way of administration and contraindications. Consideration will be given to therapy alternatives such as proper breeding management, use of uterine lavage, oxytocin/prostaglandin administration and treatment of the biofilm forma‐ tion. The idea that a better etiopathogenetical understanding of the endometritis remains the key to access to a correct diagnostic protocol and to a successful therapeutic plan will inspire this chapter.
