Effects of Origanum Syriacum Essential Oil on Blood Parameters of Broilers Reared at High Ambient Heat

The biochemical and hematological blood values of broilers fed under heat stress and that were administered Origanum syriacum (OS) essential oil were investigated in this study. In total, 400 male broilers (Ross-308; age, 1 day) were used for the period of 42-days of the study. The experiment included ten groups (n = 50/group; each group divided into five sub-groups): normal heat, 22°C: basal feed (BF)positive control group (PC), BF + 100 ppm OS; BF + 300 ppm OS; BF + 600 ppm OS). Heat stress, 36°C: BF-positive control group (PC), BF + 100 ppm SOS; BF + 300 ppm OS; and BF + 600 ppm OS). Biochemical and hematological parameters were measured in blood collected into EDTA tubes. Total bilirubin, cholesterol, low-density cholesterol, Na+, Ca2+, and Mg2+ increased, whereas alanine aminotransferase, aspartate aminotransferase, creatine kinase (CK), CK-MB, urea, uric acid, Cl–, and K+ decreased (p<0.05); however, no changes were detected in the other hematological values.


INTRODUCTION
Stress emerges from endogenous (nutrition and feeding problems, fast growth, sexual maturation period, and infection) and exogenous factors (climate, high density insufficient ventilation), and causes dire economic losses in poultry (Chenga & Muırb, 2004;Olanrewaju et al., 2006;Hadımlı et al.,2007).One stressor is high temperature which causes hyperventilation, blood pH > 7, and a decrease in plasma pyruvate kinase along with an increase in CO 2 density in the lungs; thus, causing livestock to perish within a short period (Hartlova et al., 2002;Lin et al., 2006;Al-fataftah & Abu-dieyeh, 2007) .Antibiotics have been used in the poultry industry to reduce the impact of stress, increase stock performance, and regulate gastrointestinal microflora.Nevertheless, the European Union (EU) banned antibiotics when the World Health Organization reported that microorganisms can become immune to specific antibiotics over time thus causing the emergence of resistant bacteria that pose a risk to human health (Gue et al., 2004;Yörük et al., 2008).In addition, growing sensitivity towards issues, such as human health, food safety, and environmental pollution, have emerged among consumers despite the progresses achieved in food production techniques and slaughterhouse hygiene in EU countries (Mazmanoğlu, 2008).Therefore, growing organic products by adding natural feed additives as an alternative to synthetic additives has begun in recent years.One of these alternative feed additives is thyme.Thyme is a herb in the Lamiaceae family with 40 species worldwide.Thyme contains carvacrol and thymol along with various phenolic monoterpenes.Origanum syriacum (OS) is an aromatic herb within the thyme family that grows primarily in Syria, Jordan, Lebanon, and the Sinai Peninsula, where it has different names, such as Syrian oregano, biblical hyssop,
In this study, the effects of various doses of OS essential oil added to feed as an alternative to antibiotics in broilers fed under nominal heat (22°C) and heat stressed (36°C) conditions on biochemical and hematological parameters were studied.

Poultry House Heat Moisture and Illumination
The general temperature of the poultry house was 32-33°C during the first 2 days and 27-28°C during the next 5 days.On the other hand, a 36°C temperature and 75-85% relative humidity were applied to the groups subjected to heat stress, while 22°C temperature and 55-60% relative humidity were applied to the others.All groups were provided with illumination (60 W) for 24 hours.

Feed Analyses
A proximate analyses of the feeds used for this research was performed in accordance with the methods stated in A.O.A.C 2005.

Statistical Analyses
The data were analyzed using SSPS 17.0.software (SPSS Inc., Chicago, IL, USA).Data are presented as mean ± standard error.Repeated-measures analysis of variance was used to identify if differences existed in the blood values between the groups.Duncan's multiple range test was applied to identify the group differences.A p-value < 0.05 was considered significant.

ReSUlTS
The effects of the OS essential oil added at different dosages (100, 300, and 600 ppm) on the metabolic, blood, and biochemical values are shown in Tables 2-5 Adding the OS essential oil at various dosages had no effect on most hematological values compared to the values after administering the antibiotic or heat stress.However, the OS oil did have an effect on glucose (p<0.01),liver enzymes (ALT and AST) and CK-MB (p<0.01), which indicates heart and skeletal muscle degeneration.The 600 ppm OS essential oil dosage completely protected the muscles against various pathological defects (p<0.01.

DISCUSSION
The levels of various biochemical parameters vary depending upon numerous biochemical reactions such as digestion and absorption of food.These parameters also vary with factors like strain, health, and environmental conditions (Gümüş, 2013).Blood glucose level is a biochemical indicator that increases in broilers under stress (Khaksar et al., 2012).Due to increased gluconeogenesis and activation of muscle glycogen stores after corticosterone is released from the adrenal gland.While glucose and corticosterone concentrations increase in response to stress, the number of lymphocytes decreases, which diminishes the effectiveness of the humoral and cellular defense systems (Hayırlı et al., 2005).Serum glucose level has been reported to increase in broilers as temperature rises over 30°C (Khan et al., 2002;İsmail et al., 2013;Toplu et al., 2014).In our study, the OS essential oil had no effect on blood glucose level (Table 2), and the glucose levels after exposure to heat stress were       within the normal range for broilers (Reece, 2009).

Effects of Origanum Syriacum Essential Oil on Blood Parameters of Broilers Reared at High Ambient Heat
In our study, the effects of adding OS essential oil at different dosages to the diets of the heat stressed and unstressed groups were incompatible with some previous data (Khan et al., 2002;Khaksar et al., 2012;İsmail et al., 2013).Thymol and carvacrol, which are the main components of OS, have been reported to have a cholesterol lowering property by inhibiting hepatic 3-hydrox-3-methylglutaryl coenzyme A reductase, which is a cholesterol synthesis enzyme ( Mazmanoğlu, 2008).Al-Kassie, (2009) reported that adding 200 ppm thyme oil to broiler feed significantly reduces cholesterol level.Khaksar et al. (2012) determined that 1 g/kg thyme oil in the feed of Japanese quail significantly reduces total cholesterol and TGs.Hong et al. (2012) reported that a mixture of 125 ppm thyme, anise seed, and citrus peel oils added to broiler feed significantly reduces cholesterol level.Sarıca et al. (2005) stated that 1 g/kg thyme powder added to broiler feed significantly reduces total plasma cholesterol.In contrast, Demir et al. (2005) reported that 1 g/kg origanum powder added to broiler feed significantly increases total cholesterol and TG levels, and Bölükbaşı et al. (2006) obtained similar results with 200 ppm thyme oil.In the present study, 100, 300, and 600 ppm OS added to the feed of the heat stressed broiler group (Tables 2 and 3) significantly increased HDL, LDH, TG, and total cholesterol levels.This may be attributed to decreased hepatic 3-hydrox-3methylglutaryl coenzyme A reductase enzyme activity.The high-fat diet also increased the capacity of the liver to store lipids and reduce liver function (Chawda et al., 2014).OS also reduced CK-MB (Zhang et al., 2014) and liver enzymes (ALT and AST) levels compared to the control and antibiotic groups.
Urea and uric acid are protein metabolites.Serum protein levels are important for preserving the immune system, and these values can increase under diseased or stressed conditions, such as toxicity (Arslan, 2012).Uric acid is an antioxidant that eliminates free radicals as a result of xanthine oxidase activity (Koizumi et al., 1991).Al-kassie (2009) reported that 200 ppm origanum oil in boiler feed increases total serum protein, whereas Demir et al. (2005) found the same result with 1 g/ kg origanum powder.In contrast, Köksal et al. (2012) reported a decrease in serum total protein in response to 0.75 g/kg essential oil mix (Origanum vulgare, Thymus vulgare, garlic, anise seed and raziyane).OS (300 ppm) significantly reduced urea and all dosages decreased uric acid levels in the heat stressed groups compared with those in the control and antibiotic groups in the present study.The literature has few data on urea and uric acid in broilers.
In summary, the OS essential oil showed some protective effects against heat stress in broilers.We believe that it is necessary to better understand teh effcets of origanum syriacum essential oil by testing it under various stress conditions in further future research.

ACkNOwleDgeMeNTS
This study was funded and supported by the scientific research projects commission of Atatürk University, Erzurum, Turkey (Project code: 2013-34).This manuscript is a summary of a PhD thesis from Atatürk University Institute of Health Sciences and has presented a poster in the 3rd Internatıonal Vetıstanbul Group Congress, May 17-20, 2016, Bosnia and Herzegovina.

Table 1 -
Composition and analyses of the basal diet (g/kg).

Table 3 -
Serum biochemical values in the experimental groups.

Table 2 -
Serum biochemical parameters in the experimental groups.

Table 5 -
Serum hematological in the experimental groups.