A transvaginal ultrasonic approach to elimination of singleton pregnancy in the mare: application to reduction of twin pregnancy

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references.Quarter Horse-type mares (n=36) were used to investigate transvaginal ultrasonographically-guided allantoic aspiration as a method of pregnancy reduction in the mare. Mares were randomly assigned to one of two treatment groups at Day 40-50 of gestation: 1) needle puncture of allantois and treatment with erogenous progestins (Altrenogest, 22 mg, per os, once daily, 30 days) (Group PP; n = 12), or 2) aspiration of allantoic fluid and treatment with erogenous progestins (Group AP; n = 12). Exogenous progestins were administered to simulate elevated progesterone concentrations, as would be detected if a single fetus remained viable following the termination of a twin. For comparative purposes, two treatment groups were added during the second year: 3) puncture or aspiration of the allantois without erogenous progestin treaunent (Group NP; n=8), or 4) ultrasonography without needle entry into allantois or treatment with erogenous progestins (control; Group C; n=4). Pregnancy status was monitored using transrectal ultrasonography for one week following treatment and weekly for three additional weeks. Intrauterine endoscopic examinations were performed on all mares with non-viable fetuses 30 days following treatment to identify and retrieve mummified fetuses. Fetal death occurred as a result of both allantoic puncture and aspiration procedures with a tendency (P=0.06) for fetal death rates to be higher following allantoic aspiration (I O/ 1 2; 83 %) than allantoic puncture (6/12: 50 %). The control procedure did not result in fetal death. Day of treatment affected fetal outcome in the allantoic puncture group. Fetal death rate was increased (P=0.01) when the allantois was punctured between Days 40-44 of gestation as compared with Days 4550 of gestation. Following fetal death, retained mummified fetuses occurred more often (P=0.03) in mares treated with exogenous progestins than in mares not treated with exogenous progestins. Mean plasma concentration of PGFM was higher (P=0.05) for mares in Group PP with non-viable fetuses than in Group PP mares with viable fetuses or Group AP mares with non-viable fetuses. Differences were not detected between treatment groups for mean plasma progesterone concentration