THE GROWTH PERFORMANCE AND LIPID PROFILE OF BROILERS FED DIET WITH OR WITHOUT ANTIBIOTIC AND GREEN TEA (CAMELLIA SINENSIS) EXTRACT

Received 14 March, 2021 Revised 20 April, 2021 Accepted 28 April, 2021 Online May, 2021 --------------------


INTRODUCTION
Antibiotic growth promoters (AGP) are used in poultry production for improving feed utilization, increasing general health of chickens and subsequently improving their productive performance through different modes of action (Attia et al., 2011), although excessive use of antibiotic had negative effects on environment and human health (Al-Harithi, 2002). Usage of antibiotics as growth promoter in poultry diet has been banned due to concerns about their residues in animal tissues (Roe and Pillai, 2003) and the inclusion of antibiotics to animal diet has also been banned in some parts of the world (Simon, 2006). Various plants and plant extracts having antimicrobial properties as well as growth promoting effects have been discovered as an alternative to AGP (Cross et al., 2007;Sarker et al., 2010;Toghyani et al., 2010). Green tea is a promising plants which are reported to have antioxidant (Molan et al., 2009;Sahin et al., 2010) and antimicrobial (Erener et al., 2011;Khan, 2014) activities due to the presence of polyphenols (Gramza et al., 2005;Khan, 2014). The beneficial effects of GT by-products (Yang et al., 2003;Cao et al., 2005;), extract (Shomal et al., 2012;Farahat et al., 2016) and powder (Alimohammadi-Saraee et al., 2014) on performance and health of poultry have been reported. Green tea extract is obtained from a nonoxidized and unfermented leaves of the evergreen plant Camellia sinensis that grows mainly in tropical and sub-tropical climates. The most abundant constituent of green tea extracts (GTE) is catechins which has antibacterial activities (Cao et al., 2005;Hara-Kudo, 2005), as well as antitumorigenic, anti-inflammatory, antiproliferative, antiviral, anti-parasitic and antioxidative properties (Crespy and Williamson, 2004).
The GTE is a rich source of polyphenolic compounds and could possess strong antioxidant properties (Crespy and Williamson, 2004). However, studies comparing the effects of green tea extract (GTE) and antibiotics on broiler performance are limited. The present study tested the hypothesis that GTE and antibiotics may differently influence the growth and serum lipid profile of broiler chickens.

Experimental products
The GTE used in this study was processed manually. Green tea leaves were cleaned and sun dried after collection. The leaves were grounded properly by a grinder machine. GTE was collected after mixing of dried green tea powder with distilled water that were sonicated for 3 hour, filtered and finally extracted following the methods developed by Samuel et al., (2009).

Experimental birds and husbandry
A total of 100-day-old Cobb 500 broiler chicks were randomly assigned to 5 treatments containing 4 replicates of 5 chicks each maintained in gable type open sided house. The treatments consisted of a control, diets supplemented with three levels (0.5%, 1.0% and 2.0%) of GTE and antibiotic (0.05% Oxytetracycline) that was denoted as T0, T1, T2, T3 and T4 respectively. The extract was sprayed onto a small quantity of the feed and mixed thoroughly. The remaining feed was then added gradually and mixed to ensure a uniform distribution of the extract. All diets were formulated to meet the NRC (1994) requirements of broilers. The birds were reared on two growth phases namely, starter and finisher periods ( Table  1). The temperature of the house was adapted to the stage of growth. Lighting regime was 23 h from day 1 to day 7 and 20 h from day 8 to the end of the experiment. Feed and water were provided ad-libitum throughout the experimental period.

Vaccination programme
The chicks were vaccinated against Newcastle disease (Ranikhet) and Infectious bursal disease (Gumboro) as per Table 2.

Measurements
Growth performance parameters Experimental birds were weighed initially and weekly basis for all birds from each replication for determination of initial live weight (ILW) and final live weight (FLW). Feed intake was calculated as the total feed consumed in each replication divided by the number of birds. Feed efficiency (FE) was calculated as the amount of feed consumed per unit of weight gain. Birds were checked for mortality once daily to estimate the livability percentage.

Serum lipid profile
From each treatment, birds were randomly selected for blood sampling at 35 d of age. Blood samples were collected from the wing vein into test tubes without anticoagulant, kept in the refrigerator overnight, then centrifuged to separate serum. The collected serum samples were stored at -20°C for further analysis. Triglycerides, total cholesterol and highdensity lipoprotein cholesterol (HDL-C) were determined according to the methods of Bucolo and David (1973), Zak et al., (1954) and Naito (1984) respectively. Very low-density lipoprotein cholesterol (VLDL-C) was calculated via dividing triglyceride levels by 5 and low-density lipoprotein cholesterol (LDL-C) was calculated as the difference between total cholesterol and the combined concentrations of HDL-C and VLDL-C.

Statistical analysis
The experimental design was complete randomized design (CRD). One-way analysis of variance (ANOVA) was conducted to determine the effect of the different treatments. Mean testing (least significant difference) was performed to determine whether significant differences exist among treatments at P < 0.05. All data were expressed as mean ± SEM. SPSS (Version 20.00) was used for data analysis.

Growth performance parameters
Inclusion of GTE and antibiotics in the experimental diets significantly affect the measured growth performance parameters (BW, FI and FCR) throughout the experimental periods ( Table 3). The heaviest BW and the best FCRs were observed in broilers fed on diets supplemented with 0.5% and 1.0% of GTE, respectively. A linear trend (P < 0.05) was observed in the FCR in diets containing an increasing amount of GTE. No significant difference (P > 0.05) was observed among treatments in terms of mortality (data not presented).
GTEs are considered to provide health benefits as it contain high levels of polyphenolic catechins (epigallocatechin, epigallocatechin gallate and epicatechin gallate). For instance, green tea polyphenols are thought to interact with proteins and phospholipids in the plasma membrane, regulating signal transduction pathways, transcription factors, DNA methylation, mitochondrial function and autophagy (Kim et al., 2014). Erener et al., (2011) and Shahid et al., (2013) showed a positive effect on the growth performance of broiler chickens when supplementing their diet with 200 mg/kg of GTE. Kaneko et al., (2001) observed the beneficial effect of green tea on the productive performance and lean meat production of the broilers. Sarker et al., (2010) reported that the diet containing 0.5% green tea was effective for the growth performance and meat composition of broilers.
Nevertheless, Khalaji et al., (2011) did not observe a significant improvement in growth performance in a feed diet supplemented with GTE at a level of 300 mg/kg. The unextracted green tea powder has been reported to possess a favourable effect on broiler growth performance when supplemented at levels up to 10,000 mg/kg (Kaneko et al., 2001;El-Deek et al., 2012). The source of green tea raw material, as well as the processing and extraction conditions used in the preparation of extracts, has a direct impact on the phytochemical composition of the resulting extract (Labbé et al., 2006). The growth promoting agents may have more impact when the diet used is less digestible and well-nourished, healthy chicks do not respond to antibiotic supplements provided that they are housed under the clean and disinfected conditions (Cross et al., 2007;Toghyani et al., 2010).
Increasing the level of dietary polyphenols due to increasing the inclusion rate of GTE could be responsible for the observed negative linear effect on the FCR of the current study. This effect could be attributed to the composition of the basal diet, origin and polyphenols of the green tea used and the time of harvest, the preparation method of phytogenic additive and/or the environmental conditions (Yang et al., 2009). The bird liveability in this study was very high with no significant difference among treatments. This may be due to the use of easily digestible diets, lack of disease challenges and/or rearing chickens under clean environments.

Serum lipid profile
There were significant differences (P < 0.05) in the measured serum lipid parameters (Total cholesterol, HDL and triglyceride except LDL) between broilers fed on the control diet or diets supplemented with GTE or antibiotics. Research conducted by Muramatsu et al., (1986) and Yoshino et al., (1994) confirmed the hypocholesterolimic and hypolipidemic properties of green tea polyphenols either via reduced absorption of dietary and biliary cholesterol and increased faecal excretion (Koo and Noh, 2007) and/or inhibition of cholesterol synthesis in the liver through inactivation of 3-hydroxy-3methylglutaryl coenzyme A reductase and activation of adenosine monophosphate kinase (Singh et al., 2009). Khalaji et al., (2011) revealed a significant reduction in the total cholesterol at 500 mg/kg of GTE. 1.0 and 2.0% green tea extract with lard/cholesterol diets significantly reduced blood cholesterol level in rats (Muramatsu et al., 1986). 0.5 to 1.5% green tea supplementation in broiler diets and 1.0% to 2.0% green tea powder on layers had effects on reducing the cholesterol content of broiler meat and egg yolk of layers (Uuganbayar et al., 2006).

CONCLUSION
GTE supplementation may be suitable for growth performance as it improves feed efficiency of broilers compared to antibiotic added feed. Incorporation of GTE in the feed at 0.5% is favorable to the consumers because it assists to produce broilers with less fat and cholesterol deposition without antibiotic addition. Furthermore, growth performance parameters were not adversely affected. GTE may be an efficient alternative to AGP.