Effects of Long and Short-Term Progestagen Treatments Combined with PMSG on Oestrus Synchronization and Fertility in Awassi Ewes during the Breeding Season

Ustuner B., U. Gunay, Z. Nur, H. Ustuner: Effects of Long and Short-Term Progestagen Treatments Combined with PMSG on Oestrus Synchronization and Fertility in Awassi Ewes During the Breeding Season. Acta Vet. Brno 2007, 76: 391-397. Synchronization of oestrus has been used to increase reproductive effi ciency 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 effi ciency (oestrus response, time to onset of oestrus and duration of oestrus) and fertility rate using fl uorogestone 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 signifi cantly 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 > 0.05). 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). Sheep, oestrus synchronization, artifi cial insemination, fertility 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). Recent studies (Vinoles et al. 2001; Ataman et al. 2005; Zeleke et al. 2005) have focused on the duration of the progestagen-based synchrony treatments. Intra-vaginal devices containing different types of progestagens, maintained during 6 14 days associated with or without PMSG or PMSG and ProstaglandinF2α (PGF2α) combinations have been used (Eppleston et al. 1991; Roy et al. 1999; Vinoles et al. 2001; Ungerfeld and Rubianes 2002; Ataman et al. 2005; Zeleke et al. 2005). As a result of the oestrus synchronization protocols, a high percentage of ewes show oestrus, but fertility is lower than in ewes showing natural oestrus. This low fertility rate has been attributed to changes in the hormonal milieu that results in an asynchrony between oestrus and ovulation (Scaramuzzi et al. 1988), with a subsequent alteration in sperm transport (Pearce and Robinson 1985). ACTA VET. BRNO 2007, 76: 391-397; doi:10.2754/avb200776030391 Address for correspondence: Burcu USTUNER Department of Reproduction and Artifi cial Insemination, Faculty of Veterinary Medicine, Uludag University, 16059-Gorukle, Bursa, TURKEY Phone: +90 224 2941245 Fax: +90 442 80 25 e-mail:[email protected] http://www.vfu.cz/acta-vet/actavet.htm Recently, Ungerfeld and Rubianes (1999b) found that short-term treatment (5 6 d) with different progestagen devices during the non-breeding season was as effective as long-term treatment to induce oestrus and the subsequent fertility. During the breeding season and with natural mating, Vinoles et al. (2001) obtained higher pregnancy rate after a shortterm treatment (six days of medroxyprogesterone acetate (MAP) sponges, 87%) compared to the traditional 12-day treatment either with (67%) or without (63%) an equine chorionic gonadotropin (eCG) dose at the time of sponge withdrawal. Progestagen 5-day treatment was used in combination with PGF2α to improve oestrus synchronization with good results (Vinoles et al. 2001; Menchaca and Rubianes 2004) but the potential benefi t of a shortterm treatment alone in combination with fi xed time artifi cial insemination has not yet been evaluated. 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). Also the successfulness of progestagen treatment is affected by the body condition and physiological state of ewes, breeding or artifi cial insemination (AI) time (Baril et al. 1993; Evans et al. 2004; Menchaca and Rubianes 2004). 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; however, the effect of PMSG treatment on fertility is still controversial (Baril et al. 1993; Drion et al. 2001). The aim of this study was to compare the effect of the length of a progestagen treatment (12 d vs. 6 d) on synchronization effi ciency (oestrus response, time to the onset of oestrus and duration of oestrus) and the fertility rate using FGA treatment with PMSG administration applied at different times of sponge removal. Materials and Methods Animals and experimental protocol The experiment was carried out at the Uludag University Veterinary Faculty Farm, (lat 40.1833°, long 29.0667°, alt 100 metres) in Northwestern Anatolia during the breeding season (September) under natural lighting. In this study, 68 clinically healthy fat-tailed Awassi ewes (2 to 5 year old), 3 fertile Awassi rams for semen collection and 5 teaser rams for oestrus detection were used. These teaser rams were used rotationally (changed daily). Ewes were kept away from the rams to prevent voluntary mating. In the meantime, a teaser ram was introduced to the fl ock for a short time (1 h) on each occasion (once or twice weekly) to determine the presence of oestrus cyclicality in season. Sixty-eight ewes had given birth in previous February. Their milking period terminated in August and these animals had never been treated with PMSG in the past. Body weights and condition scores of these animals were recorded prior the experiment. Ewes weighing between 50 to 85 kg with good body conditions (BCS: 3 to 4.0) were used. Lengths of progesterone administration (long term; 12d vs. short term; 6d) and time of PMSG treatment in relation to progesterone removal were studied. Ewes (n = 68) were divided into two groups; long-term (LT: 12 d, n = 33) and short-term (ST: 6 d, n = 35) groups treated with 30 mg FGA progestagen sponges (Syncro-Part®, Ceva Sante Animale, France). Ewes of each group were divided into 3 subgroups according to the PMSG (Syncro-Part® PMSG-300 IU, Ceva Sante Animale, France) treatment time. 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. Observation of oestrus signs Ewes were monitored every 6 h for 1 h starting from 12 h to 140 h after sponge removal for both the signs of oestrus behaviour and their durations with the aid of teaser rams. Ewes were considered in oestrus when they allowed the male to mount. Oestrus duration was defi ned as the time elapsed between the fi rst and last accepted mount within the same oestrus period. Oestrus cessation was defi ned as the time elapsed between sponge removal and last accepted mount within the same oestrus period. Three rams with previously proven fertility were used for semen collection with the aid of artifi cial vagina in the presence of a ewe in oestrus. Each ejaculate was immediately evaluated for volume, wave activity, motility and concentration. Only ejaculates with a volume of more than 0.5 ml, good wave activity (+++) and motility 70% and minimum 2.5 × 109 sperm cells/ml were used. The ejaculates from each ram were mixed, pooled and maintained at 30 °C. The semen was diluted to a sperm concentration of 1000 × 106 motile sperm cells/ml after being counted with the aid of a haemocytometer. A one-step dilution was performed with the addition of sterilized 392