This experimental procedure was approved by the Local Ethics Committee of Gaziosmanpasa Universty, Animal Experiments (Protocol No: 2016-HADYEK-42) dated 26.10.2016 and numbered 51879863-125.
       
The research was carried out in the Akbelen plateau in the north, 36° 40' 53" longitude (east) coordinates of 40° 26' 42" latitude, which is connected to Tokat center. The enviromental conditions and dates were collected from the meteorological service of Turkish state during the grazing period. The long term annual temperature and rainfall are 12.6°C and 431.7 mm, respectively according to the data described by TSMS (2017). This pasture is defined as a middle-class pasture, 1679 m above sea level, slightly sloping (20-30%), clay, salty and slightly acidic, lime-free brown forest soils, which was covered with 51% of grass plants (Festuta ovina,Fescuta pratenses, Poa pratensis, Poa bulbosa), 14.6% of the legume plants (Thymus serpyllum, Trigonella foenum-graecum, Hebex Andersonii Variegata, Polygonum cognatum) and 34.9% of the other species (Taraxacum officinale, Ranunculus asiaticus, Carex spiceta).
 
In this study, 3-4 year old, average 55±0.12 kg live weight and singly born, 80 heads Karayaka sheep were individually dewormed, weighed and distributed in to the their treatments groups. The concentrated feed was prepared as isocaloric and isonitrogenic according to the data described by NRC (2001) at the feed processing unit of Ferli Feed Plant in Tokat (Table 1). Fluorogesto Acetate (FGA) containing (20 mg) polyurethane foam (Chrono-gest/Sponge, Intervet, Istanbul, Turkey) were inserted into the vagina of experimental groups animal (except control) with the applicator for synchronizing estrus. After 14 days, the sponges were removed from the vagina and 600 IU per cage. Pregnant mare serum hormone (PMSG) was injected intramuscularly. Between 50 and 70 hours following the injection, oestrus of sheep were detected by rams which were apron tied around body. Sheep which synchronized oestrus were mated freely with rams (Ataman et al., 2009). All experimental animals were grazed on pasture at the same time every day. After grazing, barley and omega 3 experimental groups were fed with a concentrate of 650 g per day starting 21 days before mating and 10 days after mating. Vitamin and minerals requrements were met as per NRC (2001) (Table 1).  


      
The pasture composition was determined by harvesting the plants from the pasture area. A metal circle of 0.25 m² in diameter was randomly thrown to different parts of the pasture where the animals graze. An area of 0.25 m² was hand clipped from each of the 4 replicated plots. Pasture plants harvested 5 cm above ground level. After harvesting, herbage sample taken from pasture was separated by hand as grass, legume and other species in order to determine botanical composition. Pasture samples were dried at 70°C for 48 hours, milled and passed through a 1 mm screen to determine chemical composition. It was also burned at 525°C for 8 hours to detect organic matter and crude ash. Crude protein (CP) content of forages were determined by kjeldahl method using Tecator Block digestion and steam distillation (multiplying total N by 6.25). The acid detergent fiber (ADF) and neutral detergent fiber (NDF) contents of the feed samples were measured by the filter bag method in the ANKOM fiber analyzer (F220/220 operators Manual, Ankom tech.) by AOAC (2012). The composition of the fatty acids was determined by Gas Chromatography Flame Ionization Detector (GC-FID). The fatty acid composition of the feedstuff used as the omega-3 source in the trial was determined by the ARGEA technology company described by AOAC (2012) (Table 2).


       
Analysis of data obtained was carried out using the SPSS-X package program. The following mathematical model was used in the evaluation of the data. As a mathematical model; Yijk = G mean + ai + eijk this equality; Yijk = Observation value, G ort = Overall average, ai = Effect of feeds, eijk = Error value. X² (Chi-square, chi-square) independence test was applied in order to investigate whether there was any difference in terms of fertility and twinning rates among the experimental groups. Distribution in terms of treatment group averages Duncan’s multiple comparison test and the “t” test were used to determine the effects of oestrussynchronization between pasture and control group described by Pallant (2007).

Ovulation rate
 
The ovulation rate of experimental groups was determined 50 to 70 hours after intramuscular injection of pregnant stomach serum hormone (PMSG). Although all of the animals in pasture, barley and omega-3 groups showed oestrus, only 85 % of the animals in the control group showed oestrus (Table 3). It was determined that the difference between the control group and the research groups was significant (P<0.05). Ovulation rate was lower in the control group of grazing on pastures than in the other experimental groups. It is thought that decreasing ovulation rates in the pasture group during the mating season may be due to low biomass yield and seasional effect on natural pasture quality in the experimental area. Therefore, pasture forage can not meet the nutritional needs of the sheep during the mating season. This results in agreement with Chaturvedi et al., (2006) additionally, similiar results were obtained by Aþkýn (1982) and Baþaran and Dellal (1997) in the Akkaraman and Merinos sheep. In contrast, the ovulation rates of Anatolian Merinos sheep (Aþkýn 1988), Dorper sheep  (Zeleke et al., 2005), Manchega sheep (Gómezet et al., 2006), Çukurova meat sheep (Ocak et al., 2005) and Sanjabi and Lori sheep (Moeini et al., 2007) were lower than our findings. But, Ünal et al., (2003) stated that ovulation rate of Karayaka sheep was higher than our Fig. On the other hand, by synchronizing the oestrus of the animals in the pasture group; it was observed that the ovulation rate of this group increased compared to the control group. The difference between the two pasture groups was found to be significant (P<0.05). The highest number of lambs were obtained from the omega 3 group while the least lambs were obtained from the control group (Table 3). The difference between the groups in terms of number of lambs was statistically significant (P<0.05). Compared the effects of research groups in terms of the number of lambs born. Omega 3 polyunsaturated fatty acids group had more lambs than the other groups. The addition of polyunsaturated fatty acids to the ration during the flushing season of sheep improved fertility. It is thought that omega 3 polyunsaturated fatty acids improved the synthesis of prostaglandins by acting on the endocrine system and improve fertility functions by affecting positively on the development of eggs and embryos. This study results in agreement with Zwyrzykowska and Kupczyñský (2014) and Ambrose et al., (2006). In addition, results of Hutchinsona et al., (2012) in the Afshari sheep were similar to those of this study. Moreover, Annett et al., (2008). Conformed that when omega-3 rich fish oil was used in ruminant ration, increases the fertility rate in livestock and the number of lambs.


 
Twinning ratio
 
The twin birth was observed in omega-3 group sheep with a maximum of 7 sheep, followed by 5 sheep with pasture group and 4 sheep with barley feeding group, but in the control group, it was found that there was no twin born sheep (Table 3). Although twin birth ratios in the experimental groups were 44% in the Omega-3 group, 33% in the pasta group and 24% in the barley group, it was seen that there were no twin birth sheep in the control group. (0%). According to these results, the difference between the groups was found to be statistically significant (P<0.01). Hormonal treatments of pasture group  have improved reproductive efficiency, especially fertility and lambing rate in Karayaka sheep. In present study results were in agreement with Kia et al., (2012).
 
Fertility performance
 
Fertility results of research and control groups summarized as seen in Table 3. highest number of lambs per sheep was in  omega-3 group (1.35), followed by pasture group (1.25), barley group (1.16) and lowest in control group (0.80). The difference between groups in terms of lamb productivity was statistically significant (P<0.05). In addition to, this fertility rate of control, pasture, barley and omega-3 groups were found as 80%, 125%,116% and 135%  respectively.

Results of the above indicated that, addition of omega-3 polyunsaturated fatty acids as supplemental feeds in the flushing period increased fertility of Karayaka sheep.