engleski

The usage of hormonal serological profiles in advancement of sexual season in goats

Goats from high latitudes (>35°) and also from subtropical latitudes (25°-35°) exhibit seasonal changes in reproductive activity. The breeding season in general starts in autumn and ends in winter. Apart from hormonal methods, out-of-breeding reproduction season can be achieved using natural methods based on daylength manipulation. The introduction of males among anovulatory females can also induce ovulatory activity during anoestrus what is called “the male effect”. Following introduction of a male, goats ovulate around day 3, mostly non fertile ovulations. This is called as a non-fertile short cycle (SC). They ovulate again after 5-7 days (Normal Cycle - NC) with this second ovulation being usually fertile (SC-NC cycle). The problem of naturally induced ovulations is insufficient synchronization for application of Artificial Insemination (AI) methods in and out of the breeding season in order to obtain pregnant females. Two AI protocols after oestrus induction with male effect have been studied to evaluate their efficacy under field condition but at least 5 days of insemination were needed. Higher synchrony of ovulations would allow AI protocols to be simplified and therefore to minimise costs by reducing the number of AI. To improve the protocol, the hormone serological profiles of the Saanen goats (N=82) were made after photoperiod treatment (90 long days + 60 short days) and introduction of the males out of season and also in transitional period. Blood samples for progesterone level were drawn every day from introduction of males (D0) until D13. Blood samples for luteinizing hormone (LH) level were drawn from D5 until D9 every 4 hours. Out of season 75.9% goats developed SC-NC cycle, 93.7% of these goats exhibit oestrus during D5-D9 (8.0±0.94 days), 100% of these goats displayed preovulatory LH surge between D5-D9 (201.8±21.4 hours). In transitional period 92.3% goats developed SC-NC cycle, 94.4% of these goats exhibited oestrus during D5-D9 (6.9±0.64 days) and 100% of these goats displayed preovulatory LH surge between D5-D9 (169.9±14.6 hours). Lower number of goats developed SC-NC cycle out of season and these goats responded later to the male effect with higher variation of ovulation time.

goat, sexual season, advancement, hormonal profiles, non-hormonal method

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