Ovarian response of Suffolk ewes to estrous synchronization using short-term protocol

Abstract

-The efficacy of estrus synchronization using short-term protocol was evaluated by ultrasound exams in Suffolk ewes during the pre-breeding season. The control Group (n = 12) was synchronized by treatment for 12 days with vaginal sponges impregnated with medroxyprogesterone acetate, and 400 IU eCG at sponge withdrawal. Experimental groups I, II and III kept the sponge in place for 4 days, and 100 μg of PGF 2α was administered at sponge withdrawal. Additionally, Group I (n = 12) had 0.1 mg of estradiol benzoate (EB) administered during sponge placement and 50 μg of GnRH 48 hours after sponge removal. Group II (n = 6) had 35 mg of progesterone (P4) injected, and 0.1 mg of EB administered during sponge placement, 400 IU eCG at withdrawal and 48 hours after, 50 μg GnRH were administrated.Group III (n = 12) had 35 mg of P4 and 0.2 mg of EB administered at sponge placement, 400 IU eCG at withdrawal, and 50 μg of GnRH was administrated after 56 hours. Ovaries were monitored through ultrasound scanning. Concerning the first wave, no difference was detected between the control group and the experimental groups. However, the characteristics of ovulatory wave were significantly different between the groups. The duration of the follicular wave was shorter for Group III than for Group II. The follicle in Group I reached its maximum diameter before the Group II. The diameter of the follicle at the sponge withdrawal in the control group was larger than in Group I. After sponge withdrawal, the follicular growth rate was smaller in the control group than in Group III. The maximum diameter of the follicle in Group II was larger than in the other groups. The short-term protocol in which estrogen was used did not synchronize the emergence of the wave of follicular development.

Effects of GnRH administration on ovulation and fertility in ewes subjected to estrous synchronization

“…The GnRH treatment did not affect the efficiency of estrous synchronization (progestin with GnRH, 85.1% versus progestin without GnRH, 90.3%) and pregnancy rates after laparoscopic artificial insemination (progestin with GnRH, 53.7% versus progestin without GnRH, 61.3%). However, Takada et al (2012) reported 58.0% of Suffolk ewes ovulating, using 60 mg MAP-impregnated sponges for 4 days associated to estradiol benzoate, d-cloprostenol and 50 μg GnRH (gonadorelin) 48 hours after sponge removal.…”

“…Takada et al (2012) reported 1.17±0.17 in Suffolk ewes using 60 mg MAP-impregnated sponges for 4 days associated to estradiol benzoate, d-cloprostenol and 50 μg of GnRH (gonadorelin) 48 h after sponge removal. However, Knights et al (2001) induced estrous of 275 ewes (Suffolk and Dorset predominance) with controlled internal drug release device (CIDR) for 5 days in combination with follicle-stimulating hormone (FSH) and observed an average of 1.95±0.1 ovulations per ewe by transrectal ultrasonography.…”

Effect of different protocols for estrus synchronization on reproductive performance of Santa Inês ewes under Amazon environmental conditions

“…Initially, a supraluteal effect is expected, which means that an increase in follicular renewal may occur. In the end, however, a subluteal effect may occur and decreases the speed of follicular renewal (Takada et al, 2012).…”

Effectiveness of a low-dose Norgestomet ear implant in short-term protocols to induce estrus in ewes during the non-breeding season in Brazil.

“…production, especially where reproduction is affected by photoperiod (Takada et al, 2012). Studies have thus been performed to describe the effects of seasonality on changes in the reproductive tract of ewes and to evaluate the hormonal induction to improve fertility (Garoussi et al, 2012).…”

“…Estrus synchronization using synthetic analogues of progesterone administered through intravaginal devices is the main method used for hormonal induction and/or estrus synchronization in small ruminants (Traldi et al, 2007;Takada et al, 2012). However, the use of progesterone-releasing intravaginal devices for long periods is laborious and has been associated with the excess accumulation of vaginal mucus (Suárez et al, 2006).…”