The effects of dietary supplementation of Citrus sinensis peel extract on production and quality parameters of broiler chicken

Abstract

Citrus peel, a by-product of citrus processing is a rich source of numerous bioactive nutrients. This experiment was conducted to evaluate the effects of dietary supplementation of Citrus sinensis peel extract (CSPE) on few production and quality traits of broiler chickens. Four hundred broiler chicks (one-day-old) were assigned to any of the five dietary treatments comprised of: basal diet for 42 days, or basal diet containing 1000 ppm or 1250 ppm CSPE for 21 days, or basal diet containing 1000 ppm or 1250 ppm CSPE for 42 days. Compared to the final weight of broilers on the basal diet (2426.3 ± 120.9 g), the supplementation of the diet with 1000 ppm CSPE for 21 days resulted in significantly (P < 0.05) higher final weight (2692.5 ± 120.9 g), while that with 1250 ppm CSPE for 42 days resulted in a significantly lower (P < 0.05) abdominal fat content (47.94 vs. 28.75 ± 4.38 g). Supplementation with 1000 or 1250 ppm CSPE for 21 days or 42 days had no significant effect on the final weight, empty body weight, breast weight, thigh yield and wing yields and fresh weights and percentages of internal organ/tissues (pancreas, liver and bile, gizzard, heart) and intestinal length (duodenum, jejunum and ileum). It is concluded that citrus peel extract can be utilized as a dietary supplementation to improve the productivity (higher final weight) and quality (lower abdominal fat content) of broiler chicken.

Keywords:

• broilers
• carcass characteristics
• carcass fat
• carcass quality
• Citrus sinensis

1. Introduction

In broiler farming, feed is the single largest variable cost as providing optimal nutrition to broiler chicks often results in high cost of production and reduced profitability (Shaikh & Zala 2011). For a healthy growth of early stage broiler chicks, constant supply of high energy rations is required. However, intensive farming of broiler with excessive supply of energy dense ration results in production of meat with excessive saturated fat. Uses of chemical growth promoters such as antibiotics are associated with the danger of development of resistant microbes as well as residue contamination in the meat product (Wallinga & Bruch 2013). Therefore, feed additives which can be used safely and economically for supporting the growth of early stage broiler chicks and improving the nutritional quality of meat are needed to be identified. A number of natural bioactives such as herbal formulations (Ocak et al. 2008; Guo et al. 2010), dehydrated pasture and citrus pulp (Mourão et al. 2008) have been shown potential for improving the productivity and nutritional quality of poultry.

Citrus fruits are a rich source of bioactive nutrients including vitamin A (carotinoids and cryptoxanthin), vitamin B (thiamine, riboflavin, niacin, pyrodoxine and folate), vitamin C and minerals (Ca, Fe, Mg and K; Li et al. 2006; Parmar & Kar 2007; Bermejo et al. 2011). Citrus sinensis fruits have numerous health benefits including anti-microbial, antioxidant, immune stimulatory, anti-obesity and cholesterol lowering properties in humans (Bocco et al. 1998; Huang et al. 2009; González-Molina et al. 2010). Citrus was demonstrated to improve nutritional value of livestock products (Nam et al. 2006; Ibrahim et al. 2011).

Citrus peel is a by-product of citrus processing. Peel is considered as an edible component of the fruit which is a rich source of nutrients including vitamin C, essential oils such as terpens and aliphatic sesquiterpene and dietary fiber. The essential oils contained in the peels of C. sinensis have anti-bacterial (Prabuseenivasan et al. 2006) insecticidal and disinfectant properties (Parmar & Kar 2007). However, the health promoting effect of citrus peel preparation as a feed component of poultry have not extensively investigated. Citrus peel, being a cheap by-product with a rich content of bioactives, can be explored to improve the nutritional quality and productivity of broiler chicken. Therefore, the objective of this study was to investigate the effects of feeding of C. sinensis peel extract (CSPE) on the production and quality parameters of Ross broilers.

2. Material and methods

2.1. Experimental birds and their management

The experimental procedures involving handling and killing of the broiler chickens were approved by the Institutional Ethic Committee, and adequate care was taken to minimize the number of animals used.

Before starting the feeding trial, the poultry raring unit was thoroughly cleaned for any left over refuse of the previous batch and building complex was fumigated, washed and disinfected with 1% formalin solution. Birds were rared in scaffolding cages of 2 m (length) × 1 m (width) × 1 m (height). The raring cages, feeding and drinking units were installed and fumigated 24 hours before introducing the chick into the unit. Four hundred Ross 308 chicks (one day after hatching, average weight 43.5 g), were transferred into the raring area. During the experimental period, temperature of the building was thermostatically maintained using three gasoline rocket heaters. Water was regularly sprayed in the floor and air relative humidity was maintained at 50–60%.

On the first day, a total of 24 hrs lighting was provided which was followed by 23 hrs lighting in the subsequent days and 23 hrs daily lighting was continued during the experimental feeding period. Air conditioning was provided through use of three fans. During the first two weeks of rearing, one plastic feeding tray per cage was used. From the third week, all the feeding trays were collected and replaced by appropriate feeders. For sanitation, all drinkers were washed twice daily. Vaccination schedule was followed in accordance to Table 1. Vaccines were supplied through drinking water. To reduce the stress caused by vaccination, 24 hrs before and after vaccination a multi-electrolyte solution (1 in 1000 dilution in water) was introduced.

Table 1. Vaccination schedule.

Method of vaccination (vaccine inoculation)	Chicken age during vaccination (day)	Type of vaccine
Spray	1	Inactive IBV, AI, ND
Oral	7	IBV, ND
Oral	16	IBD
Oral	20	Clon 30 ND
Oral	30	Clon 30 ND

IBV, infectious bronchitis virus; AI, avian influenza; ND, Newcastle disease.

2.2. Preparation of citrus peel extract

The chemical composition of C. sinensis peel utilized to prepare extract is presented in Table 2. CSPE was prepared by treating the peel (40 g) with 72% ethanol (320 ml) in a water bath maintained at 50° C for 3 hrs following the method previously described (Li et al. 2006). The content was centrifuged at 3000 rpm for 10 min and the supernatant was collected and filtered by Whatman No. 42 filter paper. The filtrate was concentrated in an evaporator and completely dried in a laminar hood at room temperature.

Table 2. Chemical composition of C. sinensis peel.

Constituents	Percentage of dry weight of peel
Protein	5.46
Moisture	12.0
Dry matter	88.0
	Percentage of the dry matter
Calcium	1.1
Phosphorous	0.053
Ash	7.0
Carbohydrate	63.54
Ether extract	2.0
Fiber	10.0

2.3. Experimental diet

In this experiment, broiler chicks were fed a starter basal diet with or without supplementation of CSPE (1000 ppm or 1250 ppm) for 21 days followed by feeding the grower basal diet with or without supplementation of the CSPE (1000 ppm or 1250 ppm) for an additional 21 days. Dietary compositions and nutrient compositions of the basal diet during the starter and grower periods are presented in Tables 3 and 4, respectively. Chicks fed the basal diet without any dietary supplementation for 42 days served as control. Different dietary treatments were as follows:

Table 3. Composition of the starter and grower basal diets of broiler chicken.^a

Ingredients	Starter diet (%)	Grower diet (%)
Corn	54.32	58.69
Soybean meal	39.43	31.87
Oyster shell	0.90	0.79
Corn oil	2.16	5.83
DL-methionine	0.20	0.22
L-lysine	0.07	0.05
Digestible crude protein (DCP)	2.05	1.68
Salt	0.37	0.37
Vitamin mixture^b	0.25	0.25
Mineral mixture^c	0.25	0.25

^a Diets formulated according to the UFFDA software program based on recommendations of NRC (1994).

^b Supplied per kg of diet: 12,000 IU Vitamin A, 10 mg Vitamin E, 2200 IU Vitamin D, 35 mg niacin, 12 mg D-pantothenic acid, 3.63 mg riboflavin, 3.5 mg pyridoxine, 2.4 mg thiamine, 1.4 mg folic acid, 0.15 mg biotin and 0.03 mg Vitamin B.

^c Supplied per kg of diet: 60 mg manganese, 40 mg zinc, 1280 mg iron, 8 mg copper, 0.3 mg iodine and 0.2 mg selenium.

Table 4. Nutrient composition of the starter and grower basal diets.^a

Nutrients	Starter diet	Grower diet
Chemical analysis
Energy (ME) (kcal/kg)	2929.00	3176.00
CP (%)	21.82	19.12
EE (%)	3.10	7.30
Ash (%)	5.70	3.60
Dry matter (%)	87.90	89.80
Cl (%)	0.19	0.19
Calcium (%)	1.025	0.89
Available phosphorus (%)	0.67	0.65
Analysis results
Lysine (%)	1.15	0.96
Methionine (%)	0.50	0.48
Met + Cys (%)	0.83	0.78
Threonine (%)	0.79	0.71
DCAB (mEq/kg)	236.00	202.00

^a Diets formulated according to the UFFDA software program based on recommendations of NRC (1994).

Control: starter basal diet (21 days) + grower basal diet (21 days); 21CSPE 1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet (21 days); 21CSPE 1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet (21 days); 42 CSPE 1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet with 1000 ppm CSPE (21 days) and 42 CSPE 1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet with 1250 ppm CSPE (21 days).

The experimental feeding lasted for a total of 42 days after which birds were sacrificed.

Diets were formulated to meet the nutrient requirements of growing broiler chickens according to the National Research Council guidelines (NRC 1994) and using the user friendly feed formulation done again (UFFDA) software program.

2.4. Measurement of variables

During the period of experimental feeding, feed intake was recorded. After 42 days of experimental feeding, the chickens were humanely secreficed and following the pecking operations, head and legs were separated. Weight measurements were recorded on the whole carcass, emptied stomach contents, empty body weight, breast, thigh, wings, abdominal fat, gizzard, liver and bile, heart and pancreas. Length of different sections of the small intestine (duodenum, jejunum and ileum) was also recorded.

2.5. Statistical analysis

This study was conducted in a completely randomized design with five treatments and four replicates per treatment. Data were analyzed by Statistical Analysis System (SAS), using the generalized linear model (GLM) procedure and the statistical comparison was made by Duncan test at the 95% probability level. The data recorded as ratio or percentage was adjusted within the range between 0% and 30% into their square root. The data recorded as ratio or percentage was transformed into x^0.5 + 0.5.

3. Results

3.1. Effect of supplementation of CSPE on few production parameters

To explore the possibility of dietary supplementation of CSPE in the broiler ration, chickens were fed experimental diets for 42 days (21 days starter period followed by 21 days grower period). Dietary supplementation with 1250 ppm CSPE for 21 days (starter period) resulted in a significantly low feed intake and feed conversion ratio in the broiler chickens compared to those on the control diet (Table 5). CSPE supplementation (1000 ppm) during the starter period (0–21 days) had a significantly (P < 0.05) higher final weight (2692.5 ± 120.9 g) compared to those on the control diet (2426.3 ± 120.9 g; Table 6). Broiler ration supplemented with 1000 ppm CSPE for 21 days also resulted in numerically higher empty body weight, breast weight, thigh yield and wing weight (Table 6) compared to all other dietary treatments. In contrast, CSPE supplementation (1000 ppm or 1250 ppm) during the starter period (0–21 days) and grower period (22–42 days) had no effect on any of the production parameters measured excepting the wing weight.

Table 5. Effect of supplementation of CSPE on the performance of broiler chickens.

Dietary treatments	Feed intake (g/day)	Feed conversion ratio	Production Index	Livability (%)
Control diet	109.27^ab ± 21.97	1.73^a ± 0.03	333.92^c ± 28.47	100 ± 2.79
21CSPE1000	108.81^ab ± 21.97	1.65^ab ± 0.03	388.52^b ± 28.47	100 ± 2.79
21CSPE1250	103.76^b ± 21.97	1.48^c ± 0.03	412.24^a ± 28.47	100 ± 2.79
42CSPE1000	109.14^ab ± 21.97	1.62^b ± 0.03	373.67^b ± 28.47	93.75 ± 2.79
42CSPE1250	112.57^a ± 21.97	1.62^b ± 0.03	375.33^b ± 28.47	100 ± 2.79

Note: Within column means with different superscript letter are significantly different (P < 0.05).

Control diet: starter basal diet (21 days) + grower basal diet (21 days),

21CSPE1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet (21 days),

21CSPE1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet (21 days),

42CSPE1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet with 1000 ppm CSPE (21 days) and

42CSPE1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet with 1250 ppm CSPE (21 days).

Table 6. Effect of supplementation of CSPE on the production parameters of broiler chickens.

Dietary treatments	Final body weight (g)	Empty body weight (g)	Breast weight (g)	Thigh yield weight (g)	Wing weight (g)
Control diet	2426.3 ± 120.98^a	1703.8 ± 85.62	548.75 ± 38.28	468.75 ± 29.69	127.50^ab ± 7.05
21CSPE1000	2692.5 ± 120.98^b	1740.0 ± 85.62	621.25 ± 38.28	516.25 ± 29.69	148.75^a ± 7.05
21CSPE1250	2562.5 ± 120.98	1617.5 ± 85.62	571.25 ± 38.28	453.75 ± 29.69	125.00^b ± 7.05
42CSPE1000	2542.5 ± 120.98	1361.3 ± 85.62	573.75 ± 38.28	497.50 ± 29.69	121.25^b ± 7.05
42CSPE1250	2553.8 ± 120.98	1563.8 ± 85.62	557.50 ± 38.28	448.75 ± 29.69	127.50^ab ± 7.05

Note: Means within column with different letters are significantly different (P < 0.05).

Control diet: starter basal diet (21 days) + grower basal diet (21 days),

21CSPE1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet (21 days),

21CSPE1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet (21 days),

42CSPE1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet with 1000 ppm CSPE (21 days), and

42CSPE1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet with 1250 ppm CSPE (21 days).

3.2. Effect of supplementation of CSPE on internal organs/tissues and intestinal length

Dietary supplementation of CSPE on the fresh weights of pancreas, liver and bile, gizzard, heart and abdominal fat are presented in Table 7. While no significant differences among the five treatments were evident for fresh weight of pancreas, liver and bile, gizzard and heart and their respective percentages (Table 8), dietary CSPE had significantly (P < 0.05) alters on the abdominal fat content (Table 7) and abdominal fat percentage (Table 8) of the chickens. Compared to those on the control diet (47.94 ± 4.38 g), abdominal fat content was lowest (28.75 ± 4.38 g) when the diet was supplemented with 1250 ppm CSPE for 42 days (including 21 days starter period and 21 days grower period). This was also reflected in the abdominal fat percentage data (Table 8) where the chickens on the control diet had 1.97 ± 0.18% abdominal fat while those on 1250 ppm CSPE for 42 days had only 1.12 ± 0.18% abdominal fat.

Table 7. Effect of supplementation of CSPE on the weight of internal organs/tissues of broiler chickens.

Dietary treatments	Pancreas (g)	Liver and bile (g)	Gizzard (g)	Heart (g)	Abdominal fat (g)
Control diet	4.92 ± 0.47	60.31 ± 5.50	55.86 ± 5.07	14.22 ± 1.24	47.94 ± 4.38^ab
21CSPE1000	5.87 ± 0.47	68.79 ± 5.50	69.14 ± 5.07	14.90 ± 1.24	51.75 ± 4.38
21CSPE1250	5.29 ± 0.47	63.98 ± 5.50	63.54 ± 5.07	13.13 ± 1.24	41.88 ± 4.38^abc
42CSPE1000	5.95 ± 0.47	61.13 ± 5.50	63.52 ± 5.07	15.19 ± 1.24	36.00 ± 4.38^bc
42CSPE1250	5.39 ± 0.47	59.13 ± 5.50	63.68 ± 5.07	14.44 ± 1.24	28.75 ± 4.38^c

Note: Means within column with different letters are significantly different (P < 0.05).

Control diet: starter basal diet (21 days) + grower basal diet (21 days), 21CSPE1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet (21 days),

21CSPE1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet (21 days),

42CSPE1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet with 1000 ppm CSPE (21 days), and

42CSPE1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet with 1250 ppm CSPE (21 days).

Table 8. Effect of supplementation of CSPE on the percentage of internal organs/tissues of broiler chickens.

Dietary treatment	Pancreas percentage	Liver and bile percentage	Gizzard percentage	Heart percentage	Abdominal fat percentage
Control diet	0.20 ± 0.02	2.51 ± 0.16	2.30 ± 0.13	0.58 ± 0.03	1.97 ± 0.18^a
21CSPE1000	0.22 ± 0.02	2.53 ± 0.16	2.54 ± 0.13	0.54 ± 0.03	1.95 ± 0.18^a
21CSPE1250	0.20 ± 0.02	2.49 ± 0.16	2.48 ± 0.13	0.51 ± 0.03	1.63 ± 0.18^ab
42CSPE1000	0.23 ± 0.02	2.40 ± 0.16	2.48 ± 0.13	0.59 ± 0.03	1.44 ± 0.18^ab
42CSPE1250	0.21 ± 0.02	2.51 ± 0.16	2.24 ± 0.13	0.56 ± 0.03	1.12 ± 0.18^b

Note: Means within column with different letters are significantly different (P < 0.05).

Control diet: starter basal diet (21 days) + grower basal diet (21 days),

21CSPE1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet (21 days),

21CSPE1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet (21 days),

42CSPE1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet with 1000 ppm CSPE (21 days), and

42CSPE1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet with 1250 ppm CSPE (21 days).

Effect of dietary supplementation of CSPE on the length of duodenum, jejunum and ileum are presented in Table 9. Dietary supplementation had no effect on any of these three parameters of intestinal length of broiler chickens.

Table 9. Effect of supplementation of CSPE on the intestinal length of broiler chickens.

Dietary treatments	Duodenum (cm)	Jejunum (cm)	Ileum (cm)
Control diet	25.50 ± 1.89	51.87 ± 4.48	37.50 ± 4.01
21CSPE1000	28.00 ± 1.89	64.25 ± 4.48	44.50 ± 4.01
21CSPE1250	28.00 ± 1.89	62.75 ± 4.48	42.00 ± 4.01
42CSPE1000	29.75 ± 1.89	61.25 ± 4.48	50.75 ± 4.01
42CSPE1250	29.25 ± 1.89	66.00 ± 4.48	42.75 ± 4.01

Note: Means are not significantly different.

Control diet: starter basal diet (21 days) + grower basal diet (21 days),

21CSPE1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet (21 days),

21CSPE1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet (21 days),

42CSPE1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet with 1000 ppm CSPE (21 days), and

42CSPE1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet with 1250 ppm CSPE (21 days).

4. Discussion

The present study was conducted to evaluate the effects of dietary supplementation of C. sinensis peel, a by-product of citrus processing on few production and quality traits of broiler chickens. Young Ross broiler chicks were fed with rations supplemented with 1000 or 1250 ppm CSPE and fed during the starter (1–21 days) and grower (22–42 days) periods. Dietary supplementation of CSPE had no adverse effect on the production and quality parameters of broiler chicken up to 42 days while 1000 ppm CSPE for 21 days resulted in a higher final weight of the boiler compared to those on the basal diet. Dietary supplementation of 1250 ppm CSPE for 42 days resulted in lowered abdominal fat content. Results of this study indicated that citrus peel extract can be utilized as a dietary supplementation to improve the productivity and quality of broiler chicken.

In the present study, it was evident that dietary supplementation of 1000 ppm CSPE during the starter period (1–21 days) had increased final weight while this effect diminished when the broilers fed the same ration continuously during the grower period (22–42 days). Such an effect of CSPE in the final weight gain was also absent at higher level (1250 ppm) of CSPE in starter or grower periods. Citrus peel extract was previously found to increase the circulating total protein level in the blood of chicken which might be the result of an enhanced nutrient absorption (Akbarian et al. 2013). Apart from supplying numerous vitamins with anti-oxidant property, citrus peel extract can also inhibit the growth of pathogenic microbes and support the growth of pro-biotic microflora (Pourhossein et al. 2012) and improve absorption of nutrients in the intestinal epithelium. All these factors led to higher utilization of dietary nutrients that may ultimately lead to weight gain and carcass yield (Tollba & Mahmoud 2009). The doze and time-dependent effect of CSPE observed in this study could be linked to the fact that citrus peel extract might contain inhibitory phyto-chemicals such as oxalate, tannins, phytate, saponins and so on which might affect the performance of broiler chicken during the finisher period especially at higher doze (Oluremi et al. 2010). It was also evident that feeding of CSPE during the starter period had the lowest feed intake and most efficient feed energy conversion. Considering the approximate feed cost per kilogram live weight (Table 10), it was apparent that feeding of 1000 ppm CSPE for 21 days had the maximum profitability. Therefore, it is likely that dietary supplementation of the CSPE will improve the productivity and profitability of the broiler farm when carefully used.

Table 10. Estimated cost of production of broiler chicken with or without supplementation of CSPE in the ration.

Dietary treatments	Total feed costs per chick (Rials/chick)	Total feed costs per chick (US $/chick)	Feed cost per kg live weight (Rial/kg)	Feed cost per kg live weight ($/kg)
Control diet	57368.75	2.314	23644.54	0.953
21CSPE1000	57180.38	2.306	21236.91	0.856
21CSPE1250	54477.5	2.197	21259.51	0.857
42CSPE1000	57300.75	2.311	22537.17	0.909
42CSPE1250	59103.13	2.384	23143.21	0.933

Note: Control diet: starter basal diet (21 days) + grower basal diet (21 days),

21CSPE1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet (21 days),

21CSPE1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet (21 days),

42CSPE1000: starter basal diet with 1000 ppm CSPE (21 days) + grower basal diet with 1000 ppm CSPE (21 days), and

42CSPE1250: starter basal diet with 1250 ppm CSPE (21 days) + grower basal diet with 1250 ppm CSPE (21 days).

Chicken meat is considered as a lean meat and excessive saturated fat in broiler meat is considered unhealthy for the consumer (Wang et al. 2010). In this study, CSPE was found to reduce the abdominal fat content considerably. Citrus being an acidic fruit, it is likely that the peel extract actually contributed lowering the pH of the intestine and interfere in abundance of fatty acids (Antongiovanni et al. 2007) and micro-biota which may influence the lipid accumulation (Pourhossein et al. 2012). Further research is necessary to identify an optimum doze of CSPE which can be included in the broiler ration for maximum productivity as well as optimum fat content in the meat.

5. Conclusion

The present study investigated the effects of dietary supplementation of CSPE on few production and quality traits of broiler chickens. Results of this study showed that a higher final weight of the boiler chicken can be achieved through dietary supplementation of 1000 ppm CSPE for 21 days during the starter period while a lower abdominal fat content can be achieved through supplementation of 1250 ppm CSPE for 42 days (both starter and grower periods). It is concluded that citrus peel extract can be utilized as a dietary supplementation to improve the productivity (higher final weight) and quality (lower abdominal fat content) of broiler chicken.

Acknowledgments

We are grateful to the Islamic Azad University, Rasht Branch, Rasht, Iran and Mrs Zohreh Pourhossein and Mr Nariman Miraalami for supporting this study in the form of a postgraduate research project.