Dietary supplementation of Echinacea purpurea powder improved performance, serum lipid profile, and yolk oxidative stability in laying hens

ABSTRACT

The present study aimed to investigate the effect of supplemental Echinacea purpurea (EP) powder on performance, serum metabolites, and yolk stability in laying hens. A total of 150 Hy-Line W-36 Leghorn laying hens, 43-wk of age, were randomly assigned into the five replicate cages for each of the five experimental diets based on a completely randomized design. Dietary treatments included different levels (0, 2.5, 5, 7.5, and 10 g/kg of diet) of EP powder, which were fed to the birds during a 70-d feeding trial. Results showed that dietary addition of EP powder caused significant (P < .05) increases in egg production during both 35-d periods and increased egg mass during the second 35-d period. A significant (P < .05) increase in secondary antibody response against sheep red blood cells was observed in groups receiving EP powder. Dietary supplementation of EP powder decreased (P < .05) yolk cholesterol and malondialdehyde concentrations. Moreover, supplemental  EP decreased (P < .01) serum concentrations of triglyceride and cholesterol during the first 35-d, and resulted in increases (P < .05) in serum high-density lipoproteins during both 35-d periods. From the present findings, it can be concluded that dietary supplementation with at least 7.5 g/kg EP powder could improve egg production and decrease yolk cholesterol content. In addition, yolk oxidative stability could be improved as the result of EP supplementation of laying diets.

KEYWORDS:

• Laying hens
• Echinacea purpurea
• antibody titre
• malondialdehyde
• yolk triglycerides and cholesterol

1. Introduction

Echinacea purpurea (EP) is one of the most important medicinal herbs widely used around the world to cure common cold and other infectious diseases. Echinacea species are member of Asteracea family (Perry et al. 2001), including E. angustifolia, E. pallida, E. simulata, E. paradoxa, E. tennesseensis, E. laevigata, E. sanguinea, E. atrorubens, E. gloriosa, as well as EP (McGregor 1968). It is known that there are some bioactive components in Echinacea such as caffeic acid and alkamids, phenolic acids, polyacetylenes, glycoproteins, and polysaccharides (Bauer & Wagner 1991). Hudec et al. (2007) reported that Echinacea flower and leaves have higher phenolic components. Classen et al. (2000) indicated that arabinogalactan–protein complex originated from Echinacea stimulated phagocytosis and caused increasing tumour necrosis factor-α release. It has been also shown that EP polysaccharides caused increases in interleukin (IL)-1 and cytotoxic properties against cancer cells (Stimple et al. 1984), resulting in an increase in killer cell activity (Currier & Miller 2001). Echinacea components such as cafeic, rosmarinic, and cichoric acids had high antioxidant properties (Pellati et al. 2005; Thygesen et al. 2007), which can protect organisms against cancer, ageing, and cardiovascular diseases. It has been shown that the antioxidative effects of Echinacea components are improved when cichoric acid and alkamide are combined (Thygesen et al. 2007). In addition, it has been demonstrated that alkamides have key roles in inhibiting prostaglandin E₂ production (Lalone et al. 2009). It was reported that Echinacea prevents caspase-3 accumulation (Starvaggi-Cucuzza et al. 2008) and protects cell against apoptosis.

Zhang (2005) in his study with chickens reported that EP extract (1 g/L drinking water), applied for five days, significantly increased antibody production titres against Newcastle disease virus (NDV) and infectious bursal disease. Furthermore, Goel et al. (2002) indicated that Echinacea increased phagocytic activity of macrophages in the lung and spleen of normal rats. Similarly, it has been reported that EP could activate macrophages to stimulate interferon-γ production in association with the secondary activation of T lymphocytes (Mishima et al. 2004). Bóhmer et al. (2009) showed that the number of lymphocytes, phagocytosis rate, and NDV antibody titre were higher in laying hens fed ethanol extract of Echinacea for five days. It was also reported that helper and cytotoxic T lymphocytes, and IL-2 production were increased in Echinacea oil-fed groups than in control birds (Ma et al. 2009). Survival rate of blood peripheral cells was higher in broiler chicks fed EP (Lee et al. 2009). Ethanol extract of EP and E. pallida increased antibody response against sheep red blood cells (SRBC) and led to reduced influenza A-induced damages in mice (Bodinet et al. 2002). Rehman et al. (1999) observed that Echinacea increased the first and secondary immunoglobulin G responses in mice.

Although there are several research studies on the immunostimulative effect of Echinacea, few trials have been conducted to evaluate the influence of supplemental EP on serum lipid metabolites, egg cholesterol, and yolk oxidative stability of laying hens. The present study, therefore, was carried out to evaluate the potential impacts of Echinacea in laying hens.

2. Materials and methods

2.1. General procedure

The present study was conducted in the Poultry Research Station of Isfahan University of Technology, and all experimental protocols were approved by the Isfahan University of Technology Animal Care and Use Committee. A total of 150 Single Comb White Leghorn (Hy-Line W-36) hens of 43-wk of age were randomly distributed between five cages of five experimental diets with six hens per cage. The trial lasted for 77-d including 7-d for adaptation (wk 43 of age) and 70-d as the main trial period subdivided into two 35-d periods (44–49 and 49–54 wk of age). Dietary treatments consisted of varying levels of EP (0 as the control, 2.5, 5, 7.5, and 10 g/kg of diet), which was replaced with equal quantity of wheat bran, so that all of the diets were similar in nutrient composition. The basal experimental diet (Table 1) was formulated to meet all of the nutrient requirements consistent to Hy-Line W-36 recommendations (Hy-Line International 2007). Feed and water were provided ad libitum. The birds were housed in layer wire-floored cages, and were given artificial light (16L:8D) throughout the duration of study.

Table 1. Ingredients and chemical composition of basal diet (as-fed basis).

Items (g/kg unless stated otherwise)	43–54 wk of age
Ingredients
Corn, yellow	551.9
Soybean meal	253.7
Wheat bran^a	50.0
Sunflower oil	17.7
Monocalcium phosphate	14.7
Limestone	69.7
Oyster shell	30.0
Mineral premix^b	2.5
Vitamin premix^c	2.5
Common salt	2.9
Sodium bicarbonate	1.5
DL-Methionine	1.8
L-Lysine.HCl	0.5
L-Threonine	0.5
Nutrient composition
AMEn (MJ/kg)	11.3
Crude protein	162.5
Methionine	4.4
Methionine + cysteine	7.2
Lysine	8.9
Threonine	6.8
Tryptophan	2.3
Arginine	11.2
Calcium	41.0
Non-phytate P	4.6
Sodium	1.7

^aVarying levels of Echinacea powder (2.5–10 g/kg of diet) were included into the diets at the expense of equal amount of wheat bran, so chemical composition was similar among the experimental diets.

^bMineral premix provided per kilogram of diet: Mn (from MnSO₄.H₂O), 90 mg; zinc, 80 mg; Fe (from FeSO₄.7H₂O), 60 mg; Cu (from CuSO₄.5H₂O), 10 mg; I (from Ca (IO₃)₂.H₂O), 0.8 mg; Se, 0.3 mg; cobalt, 0.15 mg.

^cVitamin premix provided per kilogram of diet: vitamin A (from vitamin A acetate), 9000 IU; vitamin D₃, 2500 IU; vitamin E (from dl-α-tocopheryl acetate), 15 IU; vitamin B₁, 2.2 mg; vitamin B₂, 4 mg; pantothenic acid, 8 mg; vitamin B₆, 2 mg; niacin, 30 mg; vitamin B₁₂, 0.015 mg; folic acid, 0.5 mg; biotin, 0.15 mg; choline (from choline chloride 60%), 400 mg.

To prepare EP powder, dried EP (whole aerial parts) was purchased from a Medicinal Plant Institute (Pakan Bazr Institute, Isfahan, Iran). After grinding, resultant EP powder was subjected to the preliminary assessments. Briefly, the dried powder of EP (20 g) was extracted with 200 mL of a 50:50 v/v ethanol:water solution in an ultrasonic bath at room temperature. Vacuum filtration was used to remove the solid. The filtrates were pooled and the solvent was removed under vacuum at 45°C using a rotary evaporator, followed by lyophilization to obtain the dried extract. A reversed-phase high-performance liquid chromatography (Hitachi, Tokyo, Japan) was used to measure the concentrations of bioactive and phenolic components of EP, as described by Pellati et al. (2004). The concentrations of cichoric acid, caftaric acid, echinacoside, cynarin, and alkamide 8/9 were determined to be 27.79, 4.07, 0.34, 1.86, and 0.73 mg/kg of EP powder (on dry matter-basis), respectively.

2.2 Performance and egg quality measurements

Hen-day egg production was measured daily during two 35-d experimental periods. All produced eggs were recorded and weighed daily, and weights were recorded on cage basis. Feed consumption and body weight of the hens were measured at the beginning and at the end of each 35-d (wk 49 and 54 of age) period.

Egg quality parameters were evaluated every 35-d. All eggs produced during the last two days of each period were collected and egg quality indices including yolk colour, Haugh unit (HU), yolk index, eggshell thickness, and shell breaking strength were measured. HU was calculated using the formula: HU = 100 log (H + 7.57 – 1.7 W^0.37), where H is the mean height (mm) of the albumen, and W is the weight (g) of the given egg (Silversides 1994).

2.3. Immunological responses

To study the effect of EP powder on blood leukocyte subpopulations, two hens from each cage were bled at the end of the experiment. Blood samples were collected in ethylene diamine tetra acetic acid-containing tubes and stained according to the protocol described by Lucas and Jamroz (1961).

Vaccination against NDV was made on d 45 of the main trial period and antibody response to NDV was measured at d 10 post-vaccine inoculation. The haemagglutination inhibition test (Jahanian 2009) was performed to determine the antibody production titre. Two birds per cage were injected intraperitonealy with 0.5 cc of 5% SRBC suspension on d 54 and 62 of the main trial period. Thereafter, the hens (wing-banded) were bled from wing vein at 7th day after each inoculation to measure antibody response to SRBC according to the procedure described by van der Zijpp and Leenstra (1980).

2.4. Blood biochemical metabolites

Blood samples were collected on d 35 and 70 of the main trial period from two birds per cage and serum samples were analysed with an autoanalyser (Autolab, PM 4000, Autoanalyser, Medical System, Rome, Italy) for cholesterol, triglycerides, and high-density lipoproteins (HDL) concentrations using the standard kits.

2.5. Yolk parameters

The six eggs produced per each cage on the last two days of the trial period were stored for the analysis of yolk cholesterol, triglycerides, and malondialdehyde (MDA). Total yolk lipids were extracted with chloroform: methanol (2:1 vol/vol) following the procedure of Folch et al. (1957). The analysis for yolk cholesterol and triglycerides was carried out according to the methodology of Hamil and Soliman (1994). Thiobarbituric acid reactive substances of egg yolk were evaluated by the method of Dorman et al. (1995) using 1,1,3,3- tetraethoxypropane as standard after 30 days of egg storage at 4°C.

2.6. Statistical analyses

All of the data were analysed using the general linear procedures of SAS software (SAS Institute 1999) based on a completely randomized design. Contrast comparisons were performed to evaluate control birds versus Echinacea-fed groups. The treatment means were separated using the least significant difference test at P < .05 statistical level.

3. Results

Data of performance parameters are given in Tables 2 and 3. Hen-day egg production was significantly (P < .05) affected by EP supplementation of diets during both 35-d periods. Although the utilization of EP powder tended (P = .16) to increase egg mass during the first 35-d period, its use significantly (P < .05) increased egg mass during the second 35-d period. In contrast to egg production and egg mass, dietary EP supplementation had no marked effect on feed intake and egg weight.

Table 2. Effect of dietary supplementation with different levels of Echinacea purpurea powder on performance parameters of laying hens during 44–49 wk of age.

Treatments	Level (g/kg of diet)	Egg production (%)	Egg weight (g)	Egg mass (g/d per hen)	Feed intake (g/d per hen)	FCR (g feed/g egg)
Control	–	74.85^b	60.11	44.90	104.30	2.34^a
Echinacea	2.5	82.22^a^b	60.47	49.70	107.78	2.19^a^b
	5	81.41^a^b	61.02	49.68	105.58	2.13^b
	7.5	86.24^a	60.88	52.45	106.51	2.04^b
	10	77.70^b	60.40	47.01	104.48	2.24^a^b
SEM		2.33	0.69	1.50	1.85	0.10
Probability
Dietary treatments		0.0435	0.6932	0.1629	0.5127	0.0500
Control vs. Echinacea		0.0391	0.4285	0.0104	0.3619	0.0743

SEM, standard error of means.

^a,bMeans with no common superscripts within each column are significantly (P < .05) different.

Table 3. Effect of dietary supplementation with different levels of Echinacea purpurea powder on performance parameters of laying hens during 49–54 wk of age.

Treatments	Level (g/kg of diet)	Egg production (%)	Egg weight (g)	Egg mass (g/d per hen)	Feed intake (g/d per hen)	FCR (g feed/g egg)
Control	–	77.70^b	63.88	49.27^c	103.46	2.13
Echinacea	2.5	80.03^a	65.44	51.89^a^b	104.36	2.00
	5	80.52^a	65.02	52.50^a	105.80	2.03
	7.5	78.82^a^b	62.92	49.57^c	105.11	2.13
	10	77.14^b	65.02	50.15^b^c	103.69	2.07
SEM		0.65	0.83	0.66	1.47	0.08
Probability
Dietary treatments		0.0428	0.5917	0.0381	0.7315	0.2349
Control vs. Echinacea		0.0204	0.6346	0.0174	0.6237	0.3157

SEM, standard error of means.

^a,b,cMeans with no common superscripts within each column are significantly (P < .05) different.

As noted in Table 2, dietary treatments affected (P < .05) feed conversion ratio (FCR), with the lowest values assigned to the birds fed on diets supplemented with 5 and 7.5 g/kg EP. Single degree of freedom contrast comparisons showed that dietary EP supplementation improved (P = .07) FCR values compared with control diet. In contrast to the first 35-d, EP supplementation of diet had no marked impact on FCR values during the second 35-d period (Table 3).

The effects of dietary EP supplementation on egg quality measurements at wk 49 and 54 of age are presented in Tables 4 and 5, respectively. As noted, yolk index tended (P = .08) to increase in EP-fed groups compared with those fed on control diet. On the other hand, supplemental EP increased (P < .05) yolk colour score. Other egg quality indices, however, were not influenced by dietary treatments.

Table 4. Effect of dietary supplementation with different levels of Echinacea purpurea powder on egg quality indices in laying hens at wk 49 of age.

Treatments	Level (g/kg of diet)	Shell strength (kg/cm^2)	Shell thickness (mm)	HU	Yolk index	Yolk colour
Control	–	2.66	0.384	84.54	0.448	7.44
Echinacea	2.5	2.78	0.388	81.12	0.443	7.78
	5	2.71	0.391	84.88	0.455	7.90
	7.5	2.66	0.383	81.03	0.458	7.88
	10	2.13	0.387	80.67	0.462	7.79
SEM		0.33	0.01	1.76	0.01	0.15
Probability
Dietary treatments		0.4361	0.6751	0.2943	0.1746	0.2761
Control vs. Echinacea		0.3248	0.5953	0.1802	0.0825	0.0383

SEM, standard error of means.

Table 5. Effect of dietary supplementation with different levels of Echinacea purpurea powder on egg quality indices in laying hens at wk 54 of age.

Treatments	Level (g/kg of diet)	Shell strength (kg/cm^2)	Shell thickness (mm)	HU	Yolk index	Yolk colour
Control	–	2.90	0.384	84.41	0.433	8.17
Echinacea	2.5	2.73	0.382	85.81	0.452	8.30
	5	2.74	0.370	86.04	0.442	8.37
	7.5	2.71	0.381	84.65	0.450	8.24
	10	2.80	0.375	85.37	0.433	8.45
SEM		0.11	0.01	1.68	0.01	0.15
Probability
Dietary treatments		0.3452	0.6752	0.4619	0.0827	0.3193
Control vs. Echinacea		0.2009	0.2763	0.2130	0.1146	0.1842

SEM, standard error of means.

As presented in Table 6, the proportion of monocytes revealed significant differences (P < .01) in groups that received EP powder, with the highest proportion assigned to the hens fed on 7.5 g/kg EP-supplemented diet. In contrast to monocytes, EP powder had no marked effect on the proportion of other leukocyte subpopulations.

Table 6. Effect of dietary supplementation with different levels of Echinacea purpurea powder on proportion (%) of peripheral leukocyte subpopulations in 54-wk-aged laying hens.

Treatments	Level (g/kg of diet)	Lymphocytes (L)	Monocytes	Heterophils (H)	Eosinophils	H:L ratio
Control	–	70.0	1.7^b^c	27.2	1.1	0.389
Echinacea	2.5	70.3	1.9^b^c	25.8	2.0	0.367
	5	69.9	2.2^a^b	26.2	1.7	0.375
	7.5	69.3	2.9^a	25.8	2.0	0.372
	10	68.4	1.3^c	28.6	1.7	0.418
SEM		1.58	0.28	1.50	0.39	0.02
Probability
Dietary treatments		0.7124	0.0091	0.5113	0.1705	0.2246
Control vs. Echinacea		0.5017	0.1873	0.5461	0.0805	0.3096

SEM, standard error of means.

^a,b,cMeans with no common superscripts within each column are significantly (P < .05) different.

Data on antibody production titres against NDV and SRBC are given in Table 7. Although not significant, dietary inclusion of EP improved (P > .05) antibody response to NDV. Interestingly, NDV antibody titre was decreased in birds fed on diets containing 10 g/kg EP powder. Primary anti-SRBC titre was numerically higher in EP-fed groups. In contrast to primary response, SRBC antibody titre during the secondary response was significantly (P < .05) increased by dietary EP supplementation.

Table 7. Effect of dietary supplementation with different levels of Echinacea purpurea powder on antibody responses (log₂) against NDV and SRBC in laying hens.

Treatments	Level (g/kg of diet)	NDV titre	Anti-SRBC antibody titres
			Primary	Secondary
Control	–	2.98	1.92	1.85^b
Echinacea	2.5	3.25	2.38	2.40^a^b
	5	3.20	2.18	2.22^b
	7.5	3.31	1.81	2.53^a^b
	10	2.95	2.32	3.35^a
SEM		0.23	0.33	0.31
Probability
Dietary treatments		0.4287	0.3191	0.0470
Control vs. Echinacea		0.2361	0.1842	0.0116

SEM, standard error of means.

^a,bMeans with no common superscripts within each column are significantly (P < .05) different.

As noticed in Table 8, serum concentrations of triglycerides were noticeably (P < .05) lower in hens fed on EP-supplemented diets (especially at the level of 10 g/kg) during both 35-d periods. Dietary inclusion of EP powder decreased serum cholesterol levels at d 35 (P < .01) and 70 (P = .053) of the main trial period. There was a significant (P < .01) difference among dietary treatments for serum HDL concentration. Dietary inclusion of EP powder caused an increase (P < .05) in serum HDL level during both 35-d periods.

Table 8. Effect of dietary supplementation with different levels of Echinacea purpurea powder on serum lipid metabolites (mg/dl) of laying hens during different ages.

Treatments	Level (g/kg of diet)	Triglycerides		Cholesterol		HDL
		wk 49	wk 54	wk 49	wk 54	wk 49	wk 54
Control	–	1475^a	1581	216	138^a	36	16^b
Echinacea	2.5	1429^a^b	1510	176	112^b	51	16^b
	5	1400^b^c	1528	176	133^a	44	21^a
	7.5	1350^c	1536	170	120^a^b	47	22^a
	10	1338^c	1466	160	128^a^b	48	24^a
SEM		22.01	26.67	13.53	5.62	2.93	1.59
Probability
Dietary treatments		0.0074	0.1139	0.0846	0.0382	0.1224	0.0063
Control vs. Echinacea		0.0013	0.0359	0.0015	0.0531	0.0204	0.0375

SEM, standard error of means.

^a,b,cMeans with no common superscripts within each column are significantly (P < .05) different.

The effect of supplemental EP on yolk components is given in Table 9. Although there was no significant difference between experimental diets for yolk triglyceride content, inclusion of EP powder increased (P < .05) yolk triglyceride concentration. Yolk cholesterol content was lower (P > .05) in EP-fed groups than in control birds. Interestingly, dietary supplementation of EP powder decreased (P < .05) yolk MDA content.

Table 9. Effect of dietary supplementation with different levels of Echinacea purpurea powder on egg components and yolk oxidative stability in laying hens.

Treatments	Level (g/kg of diet)	Triglycerides (mg/egg)	Cholesterol (mg/egg)	MDA (ppb)
Control	–	150	141^a^b^c	297
Echinacea	2.5	178	150^a	272
	5	164	143^a^b	279
	7.5	184	130^b^c	191
	10	179	124^c	207
SEM		10.07	6.09	32.71
Probability
Dietary treatments		0.1648	0.0274	0.1209
Control vs. Echinacea		0.0107	0.2006	0.0413

SEM, standard error of means.

^a,b,cMeans with no common superscripts within each column are significantly (P < .05) different.

4. Discussion

As presented, egg production percentage was influenced by dietary EP supplementation throughout the trial period. Furthermore, dietary supplementation of EP powder at the levels of 5 and 7.5 g/kg improved (P < .05) FCR values compared with control birds. Consistent with our findings, Lee et al. (2012) observed that FCR values of EP groups were significantly lower compared with that of control birds. Similarly, Maass et al. (2005) reported that supplementation of the pressed juice of EP to starter-grower pigs resulted in a significantly lower FCR in the supplemented animals than in control group. There is evidence that administrating essential oils promotes digestive enzymes of small intestinal mucosa and improves pancreas function (Platel & Srinivasan 1996, 2000). Therefore, improvements in egg production and consequently egg mass can be attributed to the enhancement of enzyme secretions within the gastrointestinal tract. In contrast with present results, some researchers (Roth-Maier et al. 2005; Bóhmer et al. 2009) have reported that performance parameters were not affected in groups supplemented with Echinacea extract. The exact reason for this discrepancy in reported results remains to be elucidated; however, it seems that the plant origin, variety, growing conditions, storage time and conditions, animal species, presence of stressful conditions, animal health, and disease occurrence are the main contributing factors that potentially affect results.

As noticed in Table 4, yolk index was increased (P = .08) in EP-supplemented hens compared with that in those fed on control diet during the first 35-d period. Moreover, supplemental EP increased (P < .05) yolk colour score. However, other egg quality indices were not influenced by dietary treatments. It seems that an increase in yolk index is due to antioxidative properties of Echinacea. It has been documented that Echinacea components such as cafeic, rosmarinic, and cichoric acids had high antioxidant activity (Pellati et al. 2005; Thygesen et al. 2007), and can protect organisms against ageing and vascular diseases. This antioxidant potency can also protect yolk membrane against oxidation and damages, and increase standing-up quality of yolk. Increase in yolk colour score is largely due to carotenoid and phenolic components of EP. Consistent with present findings, Nasiroleslami and Torki (2011) observed that yolk colour index was increased as the result of dietary supplementation of EP extract. On the other hand, Roth-Maier et al. (2005) reported that dietary inclusion of Echinacea had no obvious effect on egg quality measurements.

The proportion of monocytes in peripheral blood was influenced by dietary supplementation of EP powder. It might be related to the phagocytosis-stimulating property of Echinacea. Consistent with our findings, Allen (2003) indicated that administration of Echinacea root stimulated phagocytosis response in broiler chicks. In contrast, O'Neill et al. (2002) and Cundell et al. (2003) found significant increases in lymphocyte proportion after feeding dried Echinacea preparations to horses and rats, respectively.

Dietary supplementation of EP caused numerical increase in NDV antibody response. Zhang (2005) in his study with broiler chicks reported that administrating Echinacea extract (1g/L drinking water) for five days resulted in a significant increase in antibody production titre against NDV. Antibody titre to NDV was decreased in hens fed on diets containing 10 g/kg EP powder. This reverse effect is probably due to the antioxidative effect of herbals such as Echinacea, as evidenced by other researchers (Wang et al. 2003; Pellati et al. 2005; Thygesen et al. 2007). It has been well documented that high levels of antioxidants could suppress immune functions in different animal species (Verhasselt et al. 1999; Rasouli & Jahanian 2011; Saiafzadeh & Jahanian 2013). As seen in Table 7, dietary EP supplementation improved SRBC antibody titre during the secondary response. It has been reported that antibody titre against SRBC was significantly increased in mice fed Echinacea extract (Bodinet et al. 2002; Zhai et al. 2007). It might be because of the immunostimulating effects of Echinacea against varying antigens.

As presented in Table 8, serum concentration of triglycerides was lower in EP-supplemented hens during both 35-d periods. In agreement with our results, it has been shown that thyme oil resulted in decreases in blood concentrations of triglycerides, low-density lipoproteins (LDL), and total cholesterol in broiler chicks (Bolukbasi et al. 2006; Lee et al. 2009). It has been reported that essential oils inhibit fatty acid synthetase complex, resulting in a reduction in serum triglycerides concentration (Jahanian & Rasouli 2012). In addition, supplemental EP reduced serum cholesterol levels in the present study. It might be due to the inhibitory effect of bioactive components of Echinacea on β-hydroxy-β-methylglutaryl coenzyme A (HMG-CoA) reductase activity, a key enzyme in cholesterol biosynthesis (Konjufca et al. 1997). Consistent with our findings, Konjufca et al. (1997) reported that feeding 30 g/kg commercial garlic power reduced the activities of HMG-CoA reductase and cholesterol 7α-hydroxylase by 40% in broiler chicks. Similarly, Qureshi et al. (1983) reported that garlic oil decreased blood triglyceride, LDL, and cholesterol levels in laying hens.

Dietary inclusion of EP powder increased serum HDL during both 35-d periods. Consistent with these findings, it has been shown that adding soy genistein to laying hens diet resulted in a decrease in serum cholesterol and an increase in HDL concentration (Saiafzadeh & Jahanian 2013). It seems that an increase in serum HDL level can probably provide cholesterol needed for the biosynthesis of steroid hormones.

The utilization of EP powder increased (P < .05) yolk triglyceride concentration (Table 9). This observation might be due to the mobilization of fat from liver to ovary to provide lipoproteins for yolk follicles growth. On the other hand, the lower yolk cholesterol content in EP-supplemented hens may be attributed to the inhibition of HMG-CoA reductase activity by Echinacea components, as proposed by Konjufca et al. (1997).

MDA is known as an index of yolk oxidative stability. As shown, supplementation of EP decreased yolk MDA content. This finding is largely due to the high antioxidant activity of Echinacea components. It has been reported that Echinacea contains bioactive components such as echinacoside, cichoric acid, and caffeic acid derivatives, which have antioxidant activity (Pellati et al. 2005; Thygesen et al. 2007). This antioxidant property could protect cells against oxidative stresses probably through reducing free radical species.

5. Conclusions

The present findings show that dietary supplementation of EP could increase egg production and egg mass in laying hens. In addition, EP has beneficial impacts on blood lipid profile, as observed by the decrease in serum cholesterol and concomitant increase in serum HDL levels. The stability of egg during storage could be increased and maintained by EP supplementation of laying diets as measured by the MDA index.

Disclosure statement

No potential conflict of interest was reported by the authors.