Kısraklarda Üreme Fizyolojisi: Endokrin Mekanizmalar, Siklus Yönetimi ve Gebelik Süreçleri
Özet
Kısraklarda östrus siklusunu yöneten endokrin mekanizmaları, siklus senkronizasyonu stratejilerini ve gebeliğin fizyolojik süreçlerini ele almaktadır. Mevsimsel poliöstrik hayvanlar olan kısraklarda üreme siklisitesi başlıca fotoperiyot tarafından düzenlenmekte olup, melatonin gün uzunluğunu hipotalamus-hipofiz-gonadal eksene aktaran temel nöroendokrin aracı olarak işlev görmektedir. Bölümde, GnRH, gonadotropinler (FSH, LH) ve ovaryan steroidler (estradiol, progesteron) başta olmak üzere östrus siklusunun hormonal düzenlenmesi; prostaglandin F2α, inhibin, oksitosin, relaksin, prolaktin ve at koryonik gonadotropini (eCG) gibi yardımcı hormonların rolleriyle birlikte ayrıntılı biçimde işlenmektedir. Luteolitik ajanlar, progestagenler, GnRH agonistleri, hCG ve yapay fotoperiyot uygulamaları dahil olmak üzere östrus senkronizasyonu ve ovülasyon indüksiyonuna yönelik klinik yaklaşımlar, endikasyon ve sınırlılıklarıyla birlikte gözden geçirilmektedir. Ayrıca, ultrasonografi, rektal palpasyon ve laboratuvar temelli (progesteron, eCG, estron sülfat) tanı yöntemleri ile gebeliğin maternal tanınması, erken teşhisi, takibi ve fetal iyilik hâlinin değerlendirilmesi ele alınmaktadır. Son olarak, doğumun fizyolojik evreleri ile doğum öncesi ve sonrası bakımda kolostrumun yenidoğan pasif bağışıklığındaki kritik rolü tartışılmaktadır. Fotoperiyodik, beslenme temelli ve endokrin regülasyonu bütüncül biçimde ele alan bu bölüm, atlarda etkili üreme yönetimi, biyoteknolojik uygulama ve sürdürülebilir verimlilik için kapsamlı bir fizyolojik temel sunmaktadır.
This chapter examines the reproductive physiology of mares, focusing on the endocrine mechanisms governing the estrous cycle, strategies for cycle synchronization, and the physiological processes of pregnancy. As seasonally polyestrous animals, mares exhibit reproductive cyclicity regulated primarily by photoperiod, with melatonin serving as the key neuroendocrine mediator linking daylength to the hypothalamic-pituitary-gonadal axis. The chapter details the hormonal orchestration of the estrous cycle—GnRH, gonadotropins (FSH, LH), and ovarian steroids (estradiol, progesterone)—alongside the roles of prostaglandin F2α, inhibin, oxytocin, relaxin, prolactin, and equine chorionic gonadotropin (eCG). Clinical approaches to estrus synchronization and ovulation induction, including luteolytic agents, progestagens, GnRH agonists, hCG, and artificial photoperiod manipulation, are reviewed alongside their indications and limitations. The chapter further addresses maternal recognition and diagnosis of pregnancy, covering ultrasonographic, rectal palpation, and laboratory-based (progesterone, eCG, estrone sulfate) diagnostic methods, as well as ongoing pregnancy monitoring and assessment of fetal wellbeing. Finally, the physiological stages of parturition and essential pre- and postpartum care, including the critical role of colostrum in neonatal passive immunity, are discussed. By integrating photoperiodic, nutritional, and endocrine regulation, this chapter provides a comprehensive physiological foundation for effective reproductive management, biotechnological application, and sustainable productivity in equine breeding practice.
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