174 EVALUATION OF THE 9-DAY PROTOCOL FOR ESTROUS SYNCHRONIZATION IN SANTA INÊS EWES

Abstract

The objective of the present study was to characterise follicular dynamics in Santa Ines (SI) during a 9-day protocol for oestrous synchronization and to evaluate the efficiency of the vaginal progesterone-releasing device Primer-PR^® (Tecnopec, Brazil). Cyclic females were used (n = 10) at the ruminant sector of the veterinary hospital of the FMVZ–USP, in March 2009. The animals had body scores between 2.5 and 3 and were of proven fertility. Ultrasound examinations were performed using an ALOKA SSD-500 Scanner (Berger, Brazil) with a linear 5.0-MHz transducer, attached to a handle to allow safe intrarectal manipulation. Examinations were performed daily from 3 days (D-3) before the day of device placement (D0) until the day of device removal (D9), and twice daily from device removal until ovulation. All ewes received 0.03 mg of prostaglandin (D-cloprostenol, Prolise^®, Tecnopec, Brazil) on D9. Ovulation was assessed by the disappearance of the growing larger follicle or follicles present in the previous examinations. Oestrous detection was performed using an intact male 3 times a day (at 10:00 a.m., 6:00 p.m., and 12:00 p.m.) from D9 until the last acceptant ewe, and blood samples were taken by jugular puncture for progesterone (P4) measurement by radioimmunoassay on solid phase (COAT-A-COUNT, Siemens, USA) from D-3 until the day of ovulation. Data were analysed by Shapiro–Wilk (PROC UNIVARIATE) using the SAS program (SAS Institute Inc., Cary, NC, USA, 2001) and shown as mean ± standard deviation. Plasma P4 concentrations between D0 and D9 were 6.56 ± 2.32 ng mL^–1, peaking between D3 and D5 (8.07 ± 2.31 ng mL^–1). Oestrous behaviour was shown 45.6 ± 12.71 h after Primer-PR^® removal. The first and the last ewe that showed oestrous behaviour was at 30 h and 66 h after Primer-PR^® removal, respectively, and the majority of ewes (50%) at 42 h. Oestrous lasted 26.40 ± 9.47 h, and the majority of ewes (70%) showed oestrous behaviour during 24 h. Ovulation occurred 73 ± 14.38 h after Primer–PR^® removal and 1.3 ± 0.48 ovulations per animal were observed. From all growing presumptively dominant follicles observed, 92.3% of them ovulated. When double ovulations occurred (n = 3), the interval between first and second ovulation was 16 ± 6.93 h. Emergence of the ovulatory follicular wave occurred at 8.5 days + 16 h after Primer–PR^® insertion. The follicles observed to continue growing had a diameter of 3.48 ± 0.28 mm when they were first detected and reached 5.63 ± 0.66 mm, with a growth rate of 0.73 ± 0.43 mm per day. A standard follicle wave within the 9-day protocol was not possible to determine, and the follicles receded in up to 4 days. In conclusion, placement of a Primer-PR^® device for 9 days resulted in synchronous oestrus and ovulation in Santa Inês ewes.