Aspekte der Reproduktionssteuerung bei Schaf und Ziege^[*]

Zusammenfassung

Die Kontrolle der Reproduktion bei kleinen Wiederkäuern spielt unter betriebswirtschaftlichen Gesichtspunkten eine wichtige Rolle. Dabei kommt der Beeinflussung der Saisonalität, der Zyklussteuerung im Hinblick auf die terminierte Besamung und der Beeinflussung der Nachkommenzahl die größte Bedeutung zu. Ziel der vorliegenden Analyse ist, basierend auf den neuen Erkenntnissen in der Reproduktionsphysiologie, international übliche Methoden im Bereich der Steuerung der Saisonalität, des Zyklus und der Ovulationsrate bei kleinen Wiederkäuern zu erläutern und einen kurzen Überblick über verschiedene Aspekte der medikamentös oder durch biologische Effekte beeinflussten Fortpflanzung bei diesen Spezies zu geben. Methodisch finden exogene Gestagene zur Zyklusinduktion oder -synchronisation und/oder Prostaglan - dinanaloga zur Beeinflussung der Lebensspanne des Gelbkörpers in Kombination mit Gonadotropingaben international breite Anwendung, doch wird über variable Fruchtbarkeitsergebnisse berichtet. Mögliche Gründe hierfür liegen unter anderem in Störungen in der Follikelentwicklung, dem Ausbleiben der Befruchtung, Beeinträchtigungen des embryonalen Überlebens und der vorzeitigen Gelbkörperregression oder sind spezies- oder rassebedingt. Um eine hohe Fertilität auch bei terminierter Besamung zu erreichen, konzentrieren sich die Anstrengungen weltweit derzeit darauf, verkürzte Behandlungsprotokolle und geeignete Dosierungen zu erarbeiten, die eine verbesserte Synchronisierung der Brunst und Ovulation unter Berücksichtigung des in Wellen erfolgenden Follikelwachstums ermöglichen. Arzneimittelrechtliche Vorschriften erschweren in Deutschland den Einsatz der kontrollierten Reproduktionstechniken.

Summary

Controlled reproduction in small ruminants is an important economic factor. Of major interest is estrus induction or synchronization as a prerequisite for timed insemination, as well as the control of seasonality and the increase of numbers of offspring, which can be achieved by medication or by taking advantage of biological effects. The aim of the review is to summarize standard techniques and research efforts in controlled reproduction in sheep and goats under consideration of the advances of knowledge in reproductive physiology. Estrus induction or synchronization is usually performed by manipulating or simulating the luteal phase of the cycle with exogenous progestagens, or with prostaglandin analogues in order to induce premature luteolysis in the presence of functional corpora lutea, while ovarian follicular development is enhanced with pituitary or extrapituitary gonadotrophins. Fertility reported following application of controlled reproductive techniques varies noticeably. This might be a result of failures in follicular develop - ment, gamete transport and fertilization, increased embryonic mortality, premature corpus luteum re - gression, or from species and breed differences. In order to improve pregnancy rates subsequent to timed artificial insemination, international research efforts concentrate on the establishment of optimal dose levels and of shortened synchronization protocols for estrus and ovulation under consideration of the ovarian dynamics. In Germany the availability of pharmaceuticals for small ruminants is restricted by national guidelines. This limits the use of controlled reproduction in these species.

Schlüsselwörter

Schaf - Ziege - Saison - kontrollierte Fortpflanzung - Brunstsynchronisation - Superovulation

Keywords

Sheep - goat - seasonality - controlled reproduction - estrus synchronization - superovulation

^* Überarbeitete Fassung eines Vortrags anlässlich der Fortbildungsveranstaltung ,,Schaf- und Ziegenkrankheiten“ der ATF in Zusammenarbeit mit der DVG-Fachgruppe ,,Krankheiten der Kleinen Wiederkäuer“ und der Klinik für Geburtshilfe, Gynäkologie und Andrologie der Groß- und Kleintiere mit Tierärztlicher Ambulanz am 3. Dezember 2005 in Gießen.

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