Age and treatment on the day of embryo transfer in recipient mares affect likelihood of pregnancy

Abstract

Objective This retrospective evaluation of data from a large commercial embryo transfer facility aimed to determine the extent to which age and treatment on the day of embryo transfer in recipient mares influence the likelihood of pregnancy.

Material and methods Embryo recovery was carried out on days 8–10 post-ovulation using transcervical uterine flushing. Recipient mares grouped according to their age were treated once on the day of embryo transfer (Day 3–8 post ovulation) and were assigned randomly to 1 of 3 groups: Mares in Group A (n=101) received antispasmodic, antimicrobial, and anti-inflammatory drugs. Mares in Group B (n=100) received gentamicin and flunixin meglumine. Group C (control) (n=103) did not receive any treatment. Detomidine (0.008 mg/kg bwt i.v.) was administered to all recipients before transfer of the embryo. The influence of treatment and recipient´s age was calculated using binary logistic regression.

Results Day 16 post-transfer pregnancy rates were highest in Group A (74/101, 73.3^a%), when compared to Group B (60/100, 60%), and Group C (57/103, 55.3^b%) (a vs b, p<0.05). Pregnancy loss rates at D45 were not different between groups, A (8/74, 10.8%), B (5/60, 8.3%), and C (6/57, 10.5%), respectively (p>0.05). Pregnancy losses were increased in recipient mares 17–22 years (33.3^a%) compared to younger recipient mares (2–6 years 7^b%, 7–11 years 10%, 12–16 years 8^b%) (a:b p<0.05). The regression model showed that the predicted probability for pregnancy after embryo transfer decreased as the age of the recipient mare increased for treated recipients in Group A (p=0.012), there was no effect of treatment and recipient´s age in Group B, and a decreased likelihood of pregnancy in recipients of advanced age (≥12 years of age) in untreated recipients (group C).

Conclusions and clinical relevance Likelihood of pregnancy increased following single administration of antispasmodic, antimicrobial, and anti-inflammatory drugs at the time of embryo transfer in recipients 2–12 years of age. Likelihood of pregnancy in recipients decreased in recipients≥12 years of age. These results, obtained under the conditions of a large commercial embryo transfer program, offer an opportunity to improve pregnancy rates in recipient mares≤12 years of age.

Zusammenfassung

Zielsetzung Mit dieser retrospektiven Auswertung der Daten einer großen kommerziellen Embryotransfereinrichtung sollte ermittelt werden, inwieweit Alter und Behandlung am Tag des Embryotransfers bei Empfängerstuten die Wahrscheinlichkeit einer Trächtigkeit beeinflussen.

Material und Methoden Die Gewinnung der Embryonen erfolgte an den Tagen 8–10 nach dem Eisprung mittels transzervikaler Gebärmutterspülung. Die Empfängerstuten, die nach ihrem Alter (2–6, 7–11, 12–16 und 17–22 Jahre) eingeteilt wurden, wurden einmal am Tag des Embryotransfers (Tag 3–8 post ovulationem) behandelt und nach dem Zufallsprinzip einer von 3 Gruppen zugeteilt: Die Empfängerstuten in Gruppe A (n=101) erhielten krampflösende, antimikrobielle und entzündungshemmende Medikamente. Die Stuten der Gruppe B (n=100) erhielten Gentamicin und Flunixin meglumine. Empfängerstuten der Gruppe C (Kontrolle) (n=103) erhielten keine Behandlung. Detomidin (0,008 mg/kg) wurde allen Empfängerstuten vor dem Embryotransfer verabreicht. Der Einfluss der Behandlung und des Alters der Empfängerstuten wurde mittels binärer logistischer Regression überprüft.

Ergebnisse Am 16. Tag nach dem Transfer waren die Trächtigkeitsraten in Gruppe A (74/101, 73,3^a %) am höchsten im Vergleich zu Gruppe B (60/100, 60%) und Gruppe C (57/103, 55,3^b %) (a vs. b, p<0,05). Die Trächtigkeitsverlustraten an Tag 45 unterschieden sich nicht zwischen den Gruppen A (8/74, 10.8%), B (5/60, 8.3%) und C (6/57, 10.5%) (p>0,05). Trächtigkeitsverluste waren bei Empfängerstuten im Alter von 17–22 Jahren (33,3^a %) im Vergleich zu jüngeren Empfängerstuten (2–6 Jahre 7^b %, 7–11 Jahre 10%, 12–16 Jahre 8^b %) erhöht (a:b p<0,05). Das Regressionsmodell zeigte, dass die vorhergesagte Wahrscheinlichkeit einer Trächtigkeit nach dem Embryotransfer bei behandelten Empfängerinnen in Gruppe A mit zunehmendem Alter der Empfängerstute abnahm (p=0,012), dass es in Gruppe B keinen Effekt der Behandlung und des Alters der Empfängerstuten gab und dass die Wahrscheinlichkeit einer Trächtigkeit bei Empfängerstuten im fortgeschrittenen Alter (≥12 Jahre) bei unbehandelten Empfängerstuten (Gruppe C, Kontrolle) abnahm.

Schlussfolgerungen und klinische Relevanz Die Wahrscheinlichkeit einer Trächtigkeit stieg nach einmaliger Verabreichung von krampflösenden, antimikrobiellen und entzündungshemmenden Medikamenten zum Zeitpunkt des Embryotransfers bei Empfängerstuten im Alter von 2–12 Jahren. Die Wahrscheinlichkeit einer Trächtigkeit nahm bei Empfängerstuten im Alter von≥12 Jahren ab. Diese unter den Bedingungen eines großen kommerziellen Embryotransferprogramms ermittelten Ergebnisse bieten eine Möglichkeit, die Trächtigkeitsraten bei Empfängerstuten≤12 Jahren zu verbessern.

Key words

Horse - recipient mare - antimicrobials - NSAIDS - fertility

Schlüsselwörter

Pferd, Empfängerstute, antimikrobielle Substanzen, NSAIDs, Fruchtbarkeit

Publication History

Received: 21 April 2023

Article published online:
06 December 2023

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