Abstract
Synchronization of oestrus has been used to increase reproductive efficiency in most animals, including ewes. The aim of the present study was to compare the effect of the length of a progestagen treatment (12 d vs. 6 d) on synchronization efficiency (oestrus response, time to onset of oestrus and duration of oestrus) and fertility rate using fluorogestone acetate (FGA) progestagen sponge treatment with pregnant mare serum gonadotropin (PMSG) administration applied at different times of sponge removal. Ewes (n = 68) were divided into two groups; long term (LT, n = 33) and short term (ST, n = 35) groups treated with FGA progestagen sponges. At the end of intravaginal sponge treatment period the animals of each group were divided into the 3 subgroups in relation to time of PMSG (300 IU) treatment. PMSG treatment was applied 24 h before sponge removal, at sponge removal and 24 h after sponge removal for LT1 and ST1, LT2 and ST2, and LT3 and ST3, respectively. Each ewe was inseminated intra-cervically twice with skim cow milk-diluted semen (1000 × 106 motile cells/ml) 40 h and 60 h after sponge removal. Non-return rates (NRR-30) were monitored from 12 day after sponge removal to 30 day with the aid of teaser rams. Onsets of oestrus response and oestrus cessation were significantly different (P < 0.05) between the ST and LT treatment groups. Synchronization of oestrus was tighter in LT than ST group. Except for oestrus cessation, other indicators studied were not different in the ST subgroups. In the ST subgroups the oestrus cessation of the ST1 (88.7 ± 15.4 h) was the shortest and differed from ST3 (120.0 ± 14.2 h) (P < 0.05). No statistical difference was observed among all studied indicators for LT groups according to application time of PMSG (P >). The NRR-30 and lambing rate of the ST and LT after timed AI were 35.7% and 31.0% and 32.1% and 28.6%, respectively (P > 0.05).
Highlights
The aim of the present study was to compare the effect of the length of a progestagen treatment (12 d vs. 6 d) on synchronization efficiency and fertility rate using fluorogestone acetate (FGA) progestagen sponge treatment with pregnant mare serum gonadotropin (PMSG) administration applied at different times of sponge removal
The aim of this study was to compare the effect of the length of a progestagen treatment (12 d vs. 6 d) on synchronization efficiency and the fertility rate using FGA treatment with PMSG administration applied at different times of sponge removal
This study showed that the length of the progestagen treatment affected oestrus response and oestrus cessation
Summary
Progestagen analogues have been widely used in small ruminants to induce and synchronize oestrus (Baril et al 1993; Romano 1996; Greyling et al 1997; Vinoles et al 1999a; Simonetti et al 2000; Vinoles et al 2001; Drion et al 2001; Ataman et al 2005; Zeleke et al 2005; Dogan and Nur 2006; Emsen and Yaprak 2006). Oestrus response and fertility vary greatly when intra-vaginal sponge is applied, depending on species, breed, co-treatment, management, breeding season and mating system (Romano 1996; Greyling et al 1997; Simonetti et al 2000; Ungerfeld and Rubianes 2002; Menchaca and Rubianes 2004; Dogan and Nur 2006; Emsen and Yaprak 2006). Various studies (Eppleston et al 1991; Menchaca and Rubianes 2004; Zeleke et al 2005) have evaluated different PMSG dose levels, injection time and alternative types of gonadotropins; the effect of PMSG treatment on fertility is still controversial (Baril et al 1993; Drion et al 2001)
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