Evaluation of cervical mucus and reproductive efficiency of seasonally anovular dairy goats after short-term progestagen-based estrous induction protocols with different gonadotropins
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The use of three different gonadotropins was tested for estrous induction in dairy goats during the non-breeding season. All does received an injection of 30 mu g of d-cloprostenol and intravaginal sponges containing 60 mg of medroxyprogesterone acetate (MAP) for 6 d plus 20 IU of porcine FSH (pFSH), 200 IU of eCG or 250 IU of hCG 24 h before sponge removal. In Experiment 1 (n = 24), ovarian ultrasound parameters were recorded and cervical mucus was evaluated daily for 5 d after sponge removal or until ovulation. In Experiment 2 (n = 80), reproductive efficiency of artificially inseminated or naturally mated does was assessed. The mean interval from sponge removal to ovulation (73.5 +/- 23.7 h), number of ovulations (1.6 +/- 0.7) and ovulatory follicle diameter (7.2 +/- 0.8 mm) did not vary (P > 0.05) among the three groups. At ovulation, cervical mucus had crystalline-striated to striated (22.2%), striated to striated-caseous (72.2%) and striated-caseous to caseous (5.6%) appearance. The largest follicle diameter was greater (P < 0.05) in does with crystalline (6.7 +/- 1.4 mm), crystalline-striated (7.2 +/- 1.1 mm) or striated (7.3 +/- 1.3 mm) mucus than in those with striated-caseous (5.3 +/- 1.4 mm) or caseous (4.5 +/- 1.1 mm) mucus. Percentage of animals exhibiting estrus (92.5%) and conception rate (60.8%) were similar (P > 0.05) among the three gonadotropins groups. Results of this study support the use of eCG (200 IU), hCG (250 IU) and pFSH (20 IU) for the estrous induction protocols in dairy goats during the non-breeding season. Cervical mucus evaluation can be used as an additional method to determine the optimil time for artificial insemination in goats.