Hormonal protocols for early resynchronization of ovulation in ewes: The use of progestagens, eCG, and inclusion of early pregnancy diagnosis with color Doppler ultrasound.

This study aimed to evaluate 1) the effect of inserting an intravaginal sponge containing medroxyprogesterone during the late luteal phase on the corpus luteum (CL) function and endogenous production of P4; 2) the effectiveness of two different equine chorionic gonadotrophin (eCG) doses on synchronization of ovulations for a resynchronization treatment; and 3) the inclusion of an early pregnancy diagnosis in an early resynchronization protocol for ovulation in ewes. For all studies, the synchronization protocol was based on a short-term protocol of six days of progestogen treatment plus one dose of prostaglandin F2alpha, one dose of eCG, and gonadorelin acetate after sponge withdrawal. For the first study, the ewes were mated with fertile rams; a second sponge was inserted in half of these ewes 12 days later, and blood samples were collected daily for six days, until sponge withdrawal. For the second study, the ewes were not mated, and received a second sponge during the same period, after which they were divided into three groups according to eCG dose (0, 200, or 300 IU). In the third study, all ewes were artificially inseminated and received the second sponge during the same period. At sponge withdrawal, pregnancy was diagnosed by color Doppler ultrasonography (DUS) of the CL, and only non-pregnant ewes were re-inseminated two days later. In the first study, serum progesterone values were similar regardless of whether an intravaginal sponge had been inserted. In the second study, the ovulation time was more concentrated in those ewes which received 200 IU of eCG. In the third study, there was no difference between the experimental groups (with or without a previous pregnancy diagnosis) in pregnancy rate at the first insemination, accumulated pregnancy rate, and pregnancy loss. The insertion of an intravaginal sponge impregnated with medroxyprogesterone acetate did not affect the endogenous production of P4. The application of 200 IU of eCG provided the best result with regard to the synchronization of ovulations in the resynchronization treatment. Also, the inclusion of an early pregnancy diagnosis with DUS is useful and improves the general results of resynchronization programs, shortening the total working period.

Early pregnancy diagnosis in ewes by subjective assessment of luteal vascularisation using colour Doppler ultrasonography.

This study was designed to evaluate early pregnancy diagnosis using colour Doppler ultrasonography (US) for luteal vascularisation assessment. In Study 1, 28 ewes were artificially inseminated (Day 0), and luteal vascularisation was assessed from Day 12 to Day 19 by two evaluators using colour Doppler US, categorising the corpus luteum (CL) on a subjective scale ranging from 1 to 4. Females bearing a CL with score 2 or greater were presumably considered pregnant. Pregnancy was confirmed on Day 30 by B-Mode US. In Study 2, a predictive pregnancy diagnosis was performed on Day 17 in 197 ewes based on the criteria described in Study 1. Pregnancy was confirmed by B-mode US on Day 45. Agreement between evaluators was verified by an intraclass correlation coefficient (ICC) and Kappa index (κ). Performance of colour Doppler US for early pregnancy diagnosis was evaluated calculating sensitivity (Sens), specificity (Spec), negative predictive values (NPV), positive predictive values (PPV) and accuracy (Ac). In Study 1, luteal vascularisation assessment was unable to predict non-pregnant animals between 12 and 14 days after insemination, as all animals still had vascularised CL, and thus were considered pregnant. The colour Doppler US performance improved progressively until Day 17, when it reached maximum values (Sens = 100%, Spec = 76%, PPV = 73%, NPV = 100% and Ac = 86%). The subjective scale for luteal irrigation assessment showed medium to good agreement among evaluators on Day 12 and Day 13 (ICC = 0.66 and 0.68, respectively), and excellent agreement from Day 14 to Day 19 (ICC = 0.90, 0.80, 0.80, 0.84, 0.95 and 0.93, respectively). Agreement was almost perfect for score 1 CLs (κ = 0.87), and moderate for scores 2, 3 and 4 CLs (κ = 0.54, 0.48 and 0.41, respectively). In Study 2, performance of colour Doppler US as a tool to predict pregnancy status in ewes on Day 17 post-insemination was as follows: Sens = 93.5%, Spec = 80.8%, PPV = 85.6%, NPV = 91.1% and Ac = 87.8%. Subjective luteal vascularisation assessment using colour Doppler US to distinguish between pregnant and non-pregnant animals was considered a reliable tool which was highly efficient beginning 17 days after breeding.