Effect of Progestagen/PMSG Treatment for Oestrus Synchronization of Tuj Ewes to be Bred after the Natural Breeding Season

Ucar O. , M. Kaya, S. Yildiz , F. Onder , M. Cenesiz , M. Uzun: Effect of Progestagen/PMSG Treatment for Oestrus Synchronization of Tuj Ewes to be Bred after the Natural Breeding Season. Acta Vet. Brno 74, 2005: 385-393. The aim of this study was to investigate the effect of pregnant mare serum gonadotrophin (PMSG) and progestagen sponge on oestrus synchronization of Tuj ewes mated after breeding season. Body weights (b.w.) and condition scores (BCS) of seventeen mature fat-tailed Tuj ewes were recorded prior to the experiment and they were divided into two compared groups. All the ewes were treated by 30 mg Chronolone-impregnated intravaginal sponges for 14 days. Ewes in the first group (Group I, n = 9) were then injected with i.m. 600 I.U. PMSG upon sponge withdrawal while others, as control (Group II, n = 8) received placebo injection only. Ewes were monitored (at 2 h intervals) for both the signs of oestrus behaviour (classified as attractivity and receptivity) and their durations over the 102 h. Non-return rates were monitored (twice daily) during day 14-21 with the aid of a fertile ram. Lambing rates and litter sizes were recorded following the 150 ± 5 days of inseminations (hand-mating). Results showed that oestrus period was significantly prolonged (P < 0.05) in Group I. Additionally, a positive significant correlation (P = 0.021, R2 = 0.345) was found between BCS in situ and the litter size, regardless of PMSG administration. Furthermore, regardless of the nature of oestrus (induced or natural) in all the ewes, there was a profound effect of BCS per se on the overall litter size (P = 0.000, R2 = 0.633). It was significantly higher in ewes that had BCS higher than both 2.0 (P = 0.001, R2 = 0.633) and 2.5 units (P = 0.001, R2 = 0.654). In conclusion, PMSG combined with progestagen sponge administration for oestrus synchronization prolonged the duration of oestrus period but with no marked effects on the nonreturn rate, lambing rate or the litter size in Tuj ewes mated after breeding season. During this period, however, body energy reserves appeared to be the major effector of the litter size. Tuj, out-of-season, PMSG, Progesterone, oestrus behaviour, lambing In general, a number of factors can affect the reproductive activity in sheep. These are: photoperiod (Ortavant et al. 1988), nutrition (Chil l iard et al. 1998; Ptaszynska 2001), social interactions (Yildiz et al. 2002ab, 2004), genetics (Ptaszynska 2001), body condition (Yildiz et al. 2002b, 2003b), progestagen (Yildiz et al. 2004), prostaglandin (Yildiz et al. 2003b), melatonin (Haresign 1992), immunisation (Ptaszynska 2001), climate and management (Hafez 1993). For oestrus synchronization in particular, synchrony device, dose of PMSG, breed, week, month and year, and body weight and feeding level may be considered for timing fixed-time inseminations (McMil lan 1994). The natural methods (e.g. ram effect) are cheaper but do not result in tight synchronization (Yildiz et al. 2002b) and must be limited to certain conditions (depending on breed and season). By contrast, pharmacological methods (i.e. hormones) are effective in closely synchronizing oestrus in the majority of situations (e.g. out-of-season), that can provide good production after fixed-time insemination (Ptaszynska 2001). Among the hormonal methods given, progestagen sponge plus PMSG has been routinely available since the early 1960s (Haresign 1992). The technique has been well adapted not only for the induction of oestrus in breeding season (Ozturkler et al. 2003) but also in outACTA VET. BRNO 2005, 74: 385–393 Address for correspondence: Dr. Omer Ucar (DVM, PhD) Kafkas University, Faculty of Veterinary Medicine Department of Reproduction and Artificial Insemination 36040, Kars, Turkey Phone: +90 474 2426801/ 1276 Fax : +90 474 2426853 E-mail: [email protected] http://www.vfu.cz/acta-vet/actavet.htm