EFFECT OF BODY CONDITION SCORE AND LIVE WEIGHT OF FERTILITY OF MERINO SHEEP AFTER INDUCTION OF OESTRUS IN THE OUT-OF-BREEDING SEASON

Оbject of the study were merino sheep raised in the farm of the Agricultural institute – Stara Zagora. The experiment was conducted with a group of 68 animals of different ages, lambing after treated with hormonal preparation according to adopted scheme during the out-of-breeding season – in May. In the experimental group were included ewes which lambed earlier without making a selection in respect to their productivity. Animals were kept under the same conditions (stall-pasture) and fed the same rations with the concentrate mixture, rough, succulent feed and grazing in quantity and composition according to their physiological status and season from the fertilization until lambing. Hormonal pattern: setting pads for sheep type Sincro-part (30mg), removing pads after 12 days and giving ewes a PMSG injection at a dose of 500 UI, applying artificial insemination at the 50-55th hour.Body condition score and live weight of the animals were determined in 4 separate periods: 1st period (after mating), 2nd period (during pregnancy), 3rd period (after lambing), 4th period (before next mating service). Improving fertility in merino sheep is significantly influenced by the preparation of ewes for the mating by reaching the respective physiological status which is expressed by score over 2.5 according to the Body condition score method and live weight over 60 kg. Animals scored 2.75-3.50 before mating have a share of 91.18% from all the sheep in the flock and have the biggest number of lambs.


Introduction
Determination of body condition score of sheep is widely used in the countries where sheep farming is well developed.Applied as an express assessment of the physiological status of the animals and opportunity for monitoring and providing for their complete nutrition, this method has significant influence over the management of the flocks.In this respect, to achieve a better production efficiency it is necessary to study the existing dependence between the Body condition score and productive traits.
An important factor for improving fertility is the intensification of propagation process.Using the method for inducing oestrus in the out-of-breeding season and application of different hormonal patterns for superovulation (Boscos et all., 2002;Jafar Yadi et all., 2011;Osama et all., 2010;Ralchev et all., 2008) would provide more lambs per ewe.
According to Torre et al. (1991), Attia at al. (2001) and Hatcher at al. (2007) live weight and determination of Body condition score in the beginning of the mating have significant influence over fertility.Sejian et al. (2009) established that ewes with Body condition score 3-3,5 have the best reproduction rate.
Due to experiments conducted, a number of researchers report that fertility is influenced by the Body condition score (Doney et al, 1982;Guerra et al., 1972;Koyuncu, 2005;Madani et al., 2009).Davoud et al. (2012) in their study found that Body condition score before mating has significant effect over the number of the newborn lambs and ewes scored 3 have a higher fertility.In our previous studies we established dependence between some selection traits and Body condition score in sheep from different productive range (Ivanova et al., 2008;Dimova et al., 2008;Slavova et al., 2009Slavova et al., , 2010)).
The object of the present study is to establish the existence of relation between the Body condition score and fertility of merino sheep after application of hormonal pattern for inducing oestrus during the out-of-breeding season.

Materials and Methods
Оbject of the study were merino sheep raised on the farm of the Agricultural institute -Stara Zagora.The experiment was conducted with a group of 68 animals of different ages, lambing after treated with hormonal preparation according to adopted scheme during the out-of-breeding seasonin May.In the experimental group were included ewes which lambed earlier without making a selection in respect to their productivity.
Animals were kept under the same conditions (stall-pasture) and fed the same rations with the concentrate mixture, rough, succulent feed and grazing in quantity and composition according to their physiological status and season from the fertilization until lambing.
Hormonal pattern: setting pads for sheep type Sincro-part (30mg), removing pads after 12 days and giving ewes a PMSG injection at a dose of 500 UI, applying artificial insemination at the 50-55th hour.Body condition score and live weight of the animals were determined in 4 separate periods: 1st period (after mating), 2nd period (during pregnancy), 3rd period (after lambing), 4th period (before next mating service).In order to define the Body condition score we used the adopted 5 point systemfrom 1 (very thin) to 5 (fattened), (Todorov, 2008;Todorov et al., 1994;Thompson and Meyer, 1994).
Data was processed statistically by using software product STATISTICA for Windows.We use Descriptive statistical analyze with levels of significance: high р<0.001;average р<0.01;low р<0.05.Data were presented on figures and tables.
The biggest increase in points of Body condition score during the second period can be observed in ewes that yeaned 2 lambswith 0,350.Differences between the groups of lambed ewes were statistically significant at р<0.01.
During the third period (after lambing) the most significant decrease in point of Body condition score is observed in ewes that have triplets -with 0,433.Differences between groups in respect to the trait which was analyzed not statistically significant at р<0.05.
The observed tendency in the Body condition score to vary according to the physiological status of the animals is unidirectional although it is different in magnitudeincreasing from the first to second evaluation as the pregnancy increases, followed by decrease after lambing and after that again increasing, connected to stabilization of physiological status and preparation of ewes for the next mating procedure.

Conclusion
Improving fertility in merino sheep is significantly influenced by the preparation of ewes for the mating by reaching the respective physiological status which is expressed by score over 2.75, according to the Body condition score method and live weight over 60 kg.Animals scored 2.75-3.50before or after mating have a share of 91.18% from all the sheep in the flock and have the biggest number of lambs.

Figure 1 .
Figure 1.Distribution of sheep type of lambing, number