The Influence of the Time of Implementation of PMSG on Some of the Reproductive Parameters in Sheep With Synchronized Oestrus - Ts. Hristova, S. Stoycheva, Ts. Maslev, I. Ralchev

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The Influence of the Time of Implementation of PMSG on Some of the Reproductive Parameters in Sheep With Synchronized Oestrus - Ts. Hristova, S. Stoycheva, Ts. Maslev, I. Ralchev
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  Biotechnology in Animal Husbandry 27 (4), p 1845-1850 , 2011 ISSN 1450-9156 Publisher: Institute for Animal Husbandry, Belgrade-Zemun UDC 636.082.4 DOI: 10.2298/BAH1104845H   THE INFLUENCE OF THE TIME OF IMPLEMENTATION OF PMSG ON SOME OF THE REPRODUCTIVE PARAMETERS IN SHEEP WITH SYNCHRONIZED OESTRUS Ts. Hristova 1 , S. Stoycheva 1 , Ts. Maslev 1 , I. Ralchev 2 1 Institute of Mountain Stockbreeding and Agriculture, 5600 Troyan, Bulgaria 2 University of Forestry, Faculty of Veterinary Medicine, Sofia, Bulgaria Corresponding author: cvet_16@abv Communication Abstract: Different schemes of PMSG treatment on some reproductive  parameters in sheep were studied. Two groups of 6 sheep each at the end of the non  breeding season were treated with vaginal sponges Chrono-gest (Intervet, Holland) containing 30 mg fluorogeston acetate (FGA). The sponges were removed 12 days after insertion. Sheep of the experimental group were injected with 500UI Folligon (Intervet, Holland) 48 hours before sponge removal whilst the corresponding control sheep were treated with the same dose Folligon at the day of of sponge withdrawal. The clinical signs of oestrus, plasma progesterone concentrations and changes in the ovarian morphology during the observation period were registered. The conception rate, fertility and twinning rate were also recorded. The results show that the earlier application of the gonadotropin influence positively the reproductive traits in ewes.  Key words:   sheep, estrous synchronization, treatment Introduction Most of the sheep breeds reared in Bulgaria exhibit seasonal reproductive rhythmicity associated with changes in the natural dark-light cycle. Different schemes of estrous synchronization has been studied in order to improve reproductive efficiency (Kusina et al., 2000)  adjusting the lambing time to the most favorable time of the year in relation to the forage availability, climatic conditions and market trends (Karaca et al., 2009) . According to  Jainudeen et al. (2000)  reproductive photoperiodicity may successfully be modified by progesterone treatment which would be expected to lengthen the luteal phase of the cycle. Ungerfeld et al. (2002 ) recommended the application of progestagens in the form of vaginal sponges for a period of 6-14 days in combination with PMSG. It was found that gonadotropins stimulate follicular growth, increase the ovulation rate  Ts. Hristova et al. 1846 and fertility and improve synchronization (Cline et al., 2001; Maurel et al., 2003;  Ralchev et al., 2008) . The aim of the current study was to evaluate the effect of the various schemes of PMSG treatment on estrous synchronization, fertility and conception rate in sheep treated with progestagen, at the end of anestrus. Materials and Methods The study was conducted in the experimental farm of the Institute of Mountain Stockbreeding and Agriculture (Troyan) in August (late anestrus). Two groups of 6 Tsigai and Drysdale crosses each were kept indoor and daily ration consisting of 1.5 kg./head meadow hay (9.98% crude protein and 34.9% crude fiber) and 0.2 kg/head concentrate (14.3% crude protein and 7.9% crude fiber) was fed. Water and salt were offered ad libitum. Each ewe received an intravaginal sponge Chrono-gest (Intervet, Holland) impregnated with 30 mg fluorogestone acetate (FGA) for 12 days. The experimental sheep were injected with 500 UI Folligon (Intervet, Holland), 48 hour before sponge removal whereas the controls received the same treatment on the day of sponge withdrawal. The onset of estrous was detected twice daily – in the morning and in the afternoon by using a teaser ram. Ewes were checked visually and were considered to be in estrous when they allowed to be mounted. Sheep in estrous were hand-mated by a ram of the corresponding breed 24 to 72 hour after sponge withdrawal. Conception rate, fertility and twinning rate were calculated according to ewe performance at lambing. Jugular venous blood samples were collected from three sheep of each group at the time of sponge insertion, on the day of their withdrawal and in two day intervals during the period of 16 days after mating. After centrifugation (4000 rpm for 10 min) the blood samples were stored at -20 0 C up to the end of the observation when they were analyzed. In both groups of sheep uterus and ovarian were monitored and photographs were taken 72 hour after sponge withdrawal and again 17 days thereafter by means of micro camera Ricohn (Ricoh company, Japan) equipped with TTL flash Karl-Schorz-Endoskope (Germany). Laparoscopy was  performed after 12 hours of food and water deprivation according to the method described by  Ralchev (1992).   Results and Discussion All ewes injected with   Folligon 48 hours before the sponge removal showed estrous 24 – 36 hours after sponge withdrawal and some sheep continued to manifest signs of estrous during the next 12 hours. In ewes injected with PMSG on the day of sponge removal estrous occurred between 48 and 60 hours after treatment. Similar response pattern to exogenous hormone treatment in anestrous ewes was observed by  Dogan and Nur (2006)  in Kivircik breed and by  Hristova et  The influence of the time ... 1847 al. (2010)  in Il de France ewes.  Bonev et al.   (2002)  also found that Il de France ewes manifested estrous 45 hours after PMGS injection. Before sponge insertion and during the first days after their withdrawal plasma progesterone concentrations were lower than 0.3 ng/ml. We also found that seventy two hours after gonadotropine   injection progesterone concentration start to increase achieving in  both groups the maximum values of 0.5 ± 0.16 and 0,4 ±0,13 ng/ml, respectively,  by the 92 nd  hour after treatment and remained elevated up to the end of the observation. Similar pattern in temporal changes of progesterone concentration was observed in Kivircik ewes treated with MAP (medroxiprogesteron acetat), 500 UI PMSG and 5 mg Dinaprost at the time of sponge removal (Ekiz and Ozcan, 2006) . Progesterone concentration started to increase 50 h after injection and at 122 h it already exceeded 0.5 ng/ml. Our results corresponded closely to the findings of  Ralchev et al. (2008) who studied the changes in plasma progesterone concentrations in Tsigai ewes injected with 500 and 1000 UI gonadotropin at the time of sponge removal during the non-breeding season. In both groups of sheep  progesterone concentration began to increase 72 h after gonadotropin injection reaching the peak levels of 0.47 and 0.33 ng/ml, respectively, by the 5 th  day post-treatment. The low level of plasma progesterone at the beginning of the estrous found in our study may be accounted for by the functional changes related to development and maturation of corpus luteum. According to  Barret et al.   (2002)   progesterone levels lower than 0.2 ng/ml may be considered as a baseline. The number of corpus luteum monitored at 72 h after sponge removal was equal in both groups whilst on day 17 it was higher in ewes injected with PMGS 48 h before sponge withdrawal (Table 1). Table 1. Data from the laparoscopy performed at 72   h and 17 days after removal of the vaginal sponges 72 nd  hour 17 th  day Sheep №  right ovary left ovary right ovary left ovary Lambs  born Experimental group 170 non-observed corpus rubrum (12 hours) normal gravid corpus luteum 2 701 3 corpora lutea normal 2 gravid corpora luteanormal 3 702 normal corpus rubrum normal 1 gravid corpus luteum  barren 704 normal 1 corpus luteum normal 1 corpus luteum 1 705 1 corpus luteum non-observed 1 corpus luteum follicles 1 706 normal corpus rubrum normal corpus rubrum barren Control group 707 cyst 1 corpus luteum normal 1 corpus luteum 1 709 normal corpus rubrum normal corpus albicans barren 710 1 corpus luteum, 3-4 cystic changes1 non-ovulated follicle1 corpus rubrum 1 corpus luteum normal 2 715 3 cysts 1 corpus luteum normal 1 corpus luteum barren 718 normal cyst normal corpus albicans barren 719 1 corpus luteum 3 cysts 1 corpus luteum normal 1  Ts. Hristova et al. 1848 The incidence of ovarian cysts tended to be higher in sheep treated with PMGS at the time of sponge removal. This, in turn, may affect plasma  progesterone concentration and influence negatively conception rate and fecundity. Generally, our results suggest that time   of PMSG treatment affect reproductive traits. Conception rate, fertility and twinning rate were 66.7%, 116.6% and 50% in experimental ewes and 50.0%, 66.6% and 33.3%, respectively, in control sheep (Figure 1). 66,7116,650,050,066,633,30,020,040,060,080,0100,0120,0140,0conception rate fertility twinningExsperimental groupContol group % Figure 1. Reproductive traits in experimental and control ewes    Koyuncu and Ozis   (2010) reported the highest values of in K  ı v ı rc ı k ewes treated over the breeding season. These authors pointed out that in ewes injected with PMSG 24 h before sponge removal conception rate, fertility and twinning rate constituted 76.7%, 132.0% и  73.9%. The corresponding values in sheep receiving the same treatment at the time of sponge withdrawal were 86.2%, 127.6% and 61.9%, respectively. Similarly,  Zeleke et al.   (2005)  found that PMSG treatment 24 h before sponge withdrawal increased fertility in sheep. The overview of findings showed that responses to hormonal treatment may vary according to breed, season, treatment regimes, management and mating system. Conclusion The data derived from the current study suggest that application of PMSG  before sponge removal affect positively reproductive performance of sheep. Folligon treatment at the time of sponge removal cause ovarian abnormalities increasing the incidences of ovarian cysts.
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