Increase of pregnancy rate after multiple periovulatory inseminations in mares

Abstract

Objective There exist differences in the reproductive behavior of stallions and mares under free-running and domestic in-hand breeding conditions. Contrary to artificial insemination programs, a stallion mates a mare multiple times per estrus under natural conditions. The objective of this study was to determine if multiple periovulatory artificial inseminations (MI), four times in two different time intervals instead of two, would result in increased pregnancy outcome or higher incidences of breeding induced endometritis.

Material and methods Eighty-two estrous mares were allocated randomly to one of three experimental groups. They were administered intramuscular deslorelin (1.25 mg) to induce ovulation, and 24 hours later, they were inseminated either twice (group DI), four times in relatively short intervals (group MISI) or four times in relatively long intervals (MILI), after division of one commercial insemination dose (either frozen-thawed or chilled-warmed semen) into two or four portions, respectively. Uterine sampling for bacteriological and cytological analysis was conducted directly before the first insemination and 24 hours after the last insemination.

Results Mares of the MI groups showed a higher pregnancy rate with frozen-thawed semen than mares of the DI group. There was no difference in bacteriological and cytological results between the three groups. In addition, mares of the MISI group showed less intrauterine fluid accumulation 24 hours after the last insemination than mares of the DI and MILI groups.

Conclusion and clinical relevance We suggest that multiple periovulatory inseminations with frozen-thawed semen in a close time frame to ovulation lead to an increase of pregnancy results per cycle, and that they do not lead to impaired inflammatory reactions of the uterus in healthy fertile mares.

Zusammenfassung

Gegenstand und Ziel Zwischen freilebenden und unter domestizierten Bedingungen gehaltenen Hengsten und Stuten bestehen deutliche Unterschiede im Reproduktionsverhalten. Im Gegensatz zum Prozedere bei der künstlichen Besamung paart sich der Hengst in der Natur während eines Zyklus mehrmals mit der Stute. Ziel dieser Studie war zu bestimmen, ob vierfache Besamungen in verschiedenen Zeitabständen zur Ovulation, im Gegensatz zu zweifachen, in einer höheren Trächtigkeitsrate resultieren und ob solche Mehrfachbesamungen eine erhöhte Inzidenz von belegungsinduzierter Endometritis nach sich ziehen.

Material und Methoden Insgesamt 82 zyklische Stuten verschiedener Rassen wurden nach dem Zufallsprinzip einer von drei Behandlungsgruppen zugeteilt. Danach wurden sie im Rahmen einer standardisierten Untersuchung und 24 Stunden nach einer Ovulationsinduktion mittels 1,25 mg Deslorelin intramuskulär zweimal (Gruppe DI) oder viermal (Gruppe MI) mit entweder Kühl- oder Gefriersperma besamt, wobei die Besamungen in der Gruppe MI in Kurzzeit- (Gruppe MISI) oder Langzeit-Intervallen (Gruppe MILI) erfolgten. Hierzu wurde jeweils eine Besamungsdosis in zwei bzw. vier Portionen aufgeteilt. Direkt vor der ersten Besamung sowie 24 Stunden nach der letzten Besamung wurden eine bakteriologische und eine zytologische Untersuchung durchgeführt.

Ergebnisse Stuten der MI-Gruppe wiesen bei Verwendung von Gefriersperma eine signifikant höhere Trächtigkeitsrate pro Zyklus auf als Stuten der DI-Gruppe. Die bakteriologischen und zytologischen Befunde differierten zwischen den drei Gruppen nicht signifikant. In der MISI-Gruppe wiesen signifikant weniger Stuten Flüssigkeit im Uterus auf als in der MILI- und DI-Gruppe.

Schlussfolgerung und klinische Relevanz Die Ergebnisse der Studie deuten darauf hin, dass multiple periovulatorische Besamungen mit Gefriersperma zu einer Erhöhung der Trächtigkeitsrate führen und es dabei bei gesunden, fertilen Stuten nach der Besamung zu keiner Zunahme von Entzündungsreaktionen und mikrobieller Kontamination des Uterus kommt.

Key words

Artificial insemination - bacteriology - cytology - fertility - horse

Schlüsselwörter

Künstliche Besamung - Bakteriologie - Zytologie - Fruchtbarkeit - Pferd

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