The use of progesterone-supplemented Co-synch and Ovsynch for estrus synchronization and fixed-time insemination in nulliparous Saanen goat


Abstract: The effect of Chronogest-supplemented Ovsynch and Co-synch protocols on estrus synchronization, follicular development, and fertility after fixed-time insemination was investigated in goats during the breeding season. Co-synch (n = 24) and Ovsynch (n = 25) protocols were applied to nulliparous does with a body weight of more than 30 kg. The onset and duration of estrus were determined with teaser bucks. The does were laparoscopically inseminated with 11.5 × 10^6 motile spermatozoa/straw at the second gonadotropin-releasing hormone (GnRH) injection for Co-synch and 8 h after the second GnRH injection for Ovsynch. The rates of estrus exhibited in the does were 92% and 84% and the times from sponge removal to the onset of estrus were 31.1 h and 30.9 h; the duration times were 34.4 h and 29.4 h for Co-synch and Ovsynch, respectively (P > 0.05). The follicle diameters at the second GnRH injection were 0.72 cm and 0.68 cm, and the number of ovulations was 2.6 and 2.8 for Co-synch and Ovsynch, respectively. There were no significant differences between the Co-synch and Ovsynch groups for the nonreturn rate within 30 days (NRR_{30}) (62% and 40%) and the pregnancy rates (38% and 24%) determined on day 30. The kidding and prolificacy rates were 38% and 1.4 for the Co-synch-treated goats and 24% and 1.2 for the Ovsynch-treated goats (P > 0.05). The Co-synch protocol could yield better results compared to the Ovsynch protocol, which was related to the variation in ovulation time during the onset of puberty and the breeding season. Further studies should be done to determine the best time for fixed-time insemination and the acceptable insemination dose to improve the fertility results after timed artificial insemination in does.

Keywords: Goat semen, timed artificial insemination, Ovsynch, laparoscopy, progesterone

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