Impact of dietary dandelion (Taraxacum mongolicum Hand. -Mazz.) supplementation on carcase traits, breast meat quality, muscle fatty and amino acid composition and antioxidant capacity in broiler chickens

Abstract

This trial was performed to determine the effects of dietary supplementation of dry dandelion (Taraxacum mongolicum Hand. -Mazz.) on carcase traits, breast meat quality, muscle fatty and amino acid composition and antioxidant capacity of broiler chickens. A total of 120 Arbour Acres broiler chickens were randomly allotted to three groups and fed basal diet (CON), basal diet supplemented with 0.5 g/kg (LD) or 1.0 g/kg (HD) of dandelion. The results showed that compared with LD group, the eviscerated percentage of HD group tended to be higher (p = 0.090), while the abdominal fat yield tended to be lower (p = 0.078). In addition, dandelion quadratically increased redness, water loss rate, the proportion of C20:2, C20:4n-6, C22:6n-3 and the sum of n-3 PUFA and decreased cooking loss of Pectoralis major (PA) muscle (p < 0.05). The crude protein content of PA muscle showed a linear decrease trend with increasing dandelion levels (p = 0.057). The thiobarbituric acid reactive substance (TBARS) values on d 3 and d 5 were linearly and quadratically decreased (p < 0.05). The results indicated that dandelion could be used as natural antioxidant in broiler chickens’ diets to benefit meat quality and lipid oxidative stability.

Highlights

• Dietary dandelion quadratically increased redness value and proportion of PUFA, while decreased cooking loss of Pectoralis major muscle.

• The thiobarbituric acid reactive substance values of Pectoralis major muscle on d 3 and d 5 were linearly and quadratically decreased by dietary dandelion supplementation.

• The beneficial effect of 0.5 g/kg of dandelion was superior to 1.0 g/kg.

Keywords:

• Dandelion
• carcase trait
• meat quality
• lipid oxidation
• broiler

Introduction

Chickens is one of the most consumed meat products in China. To meet increasing demand for chickens, intensive broiler production systems were widely applied in China and worldwide. However, chickens reared under an intensive production system exposed to stressful situations, including high-stocking density, heat, vaccination, handling, feed quality and transportation (Temple and Manteca 2020). These stressors can cause oxidative stress, thereby leading to a decline in performance and poor meat quality (Estévez 2015). Dietary supplementation with antioxidants can be an effective strategy for conquering the harmful effects of oxidative stress (Farahat et al. 2016; Habibian et al. 2016; Chauhan et al. 2021). In recent years, many papers have proved the beneficial effects of herbs as natural antioxidants on the growth performance of broilers and the quality of their derived products (Saleh et al. 2018; Pliego et al. 2022).

Dandelion, as a common traditional Chinese herb, is widely distributed in China. The main bioactive ingredients of dandelion have been found to be polysaccharides, polyphenol and flavonoids (Mahboubi and Mahboubi 2020). Furthermore, the prebiotic, antibacterial, anti-inflammatory and anti-cancer activities of dandelion have been well demonstrated (Grauso et al. 2019). Previous research has shown that flavonoid and polysaccharide from dandelion exhibited stronger free radicals scavenging activity in vitro (Huang and Gu 2016; Cai et al. 2019). Xue et al. (2017) found that chicory acid, a major polyphenol of dandelion, suppressed reactive oxygen species (ROS) production in HT-29 cells induced by hydrogen peroxide. In addition, dandelion extract increased superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) activities in the liver of rats (Gulfraz et al. 2014). Based on the above studies, dandelion can be considered as a potential natural antioxidant for animal production.

In recent years, the growth promoting effect of dandelion has been demonstrated in poultry and livestock (Al-Kassi and Witwit 2009; Qureshi et al. 2015; Zhao et al. 2019; Mao et al. 2022). The addition of dandelion enhanced serum antioxidant capacity by increasing the antioxidative enzymes activities and total antioxidant capacity (T-AOC) level of laying hens (Li et al. 2022) and weaned pigs (Xu et al. 2022). Furthermore, Samolińska et al. (2020) found that dietary lyophilised dandelion root powder supplementation increased polyunsaturated fatty acids content in Longissimus lumborum muscle of growing-finishing pigs. It is suggested that dandelion as a natural antioxidant might have potentially beneficial effects on meat quality and antioxidant capacity of broilers. Therefore, the aim of this study was to investigate the effects of dietary supplementation of dandelion on the carcase traits, breast meat quality, muscle fatty and amino acid composition, antioxidant capacity and meat lipid oxidation of broilers.

Materials and methods

Animal, experimental design and diets

The animal management regimen and model for broilers that yielded the tissues for the present experiment have been reported by Mao et al. (2022). Briefly, 120 one-day-old Arbour Acres broiler chickens of similar initial weights were obtained from a commercial hatchery. All broilers were randomly divided into 3 groups with 5 replicates of 8 birds each. Birds in the control group (CON) were fed corn-soybean meal basal diet, and birds in the other two groups (LD and HD) were administered basal diet supplemented with 0.5 and 1.0 g/kg dandelion, respectively. Two basal diets were used: a starter ration from 0 to 21 d and a finisher ration from 22 to 42 d. The basal diets were formulated to meet the nutrient recommendations of the Feeding Standard of Chicken, China (NY/T 33–20042004, 2004; Chinese Ministry of Agriculture). The ingredients and chemical composition of the basal diets are presented in Table 1. The dried dandelion used in this experiment was purchased from the local market in Hohhot (Inner Mongolia, China), and the contents of polysaccharides, polyphenols and flavonoids of dandelion were 117.11, 23.92 and 35.00 mg/ml, respectively.

Table 1. Ingredients and nutritional composition of the basal diet (air-dry basis).

Item	d 0–21	d 22–42
Ingredients (g/kg)
Corn	525.00	588.00
Soybean meal	400.00	338.00
Soybean oil	30.00	30.00
Dicalcium phosphate	19.00	18.00
Limestone	10.80	12.20
Salt	3.70	3.70
L-Lysine·HCl (78%)	0.50	0.30
DL-Methionine	1.90	0.70
Vitamin and minerals premix^a	8.00	8.00
Choline	1.10	1.10
Total	1000.00	1000.00
Nutritional level^2
Metabolic energy (MJ/kg)	12.42	12.62
Crude protein (%)	22.27	19.24
Ether extract (%)	4.69	5.45
Crude fibre (%)	3.50	3.26
Total phosphorus (%)	0.59	0.67

^aPremix provided the following per kilogram of diet: retinol, 0.27 mg; cholecalciferol, 0.075 mg; tocopherol, 26 mg; menadione, 1.20 mg; thiamine, 3.00 mg; riboflavin, 8.00 mg; pyridoxine, 4.40 mg; cyanocobalamin, 0.012 mg; nicotinic acid, 45 mg; folic acid, 0.75 mg; biotin, 0.20 mg; choline, 1100 mg; calcium pantothenate, 15 mg; Fe, 100 mg; Cu, 10 mg; Zn, 108 mg; Mn, 120 mg; I, 1.5 mg; Se, 0.35 mg.

^bMetabolic energy was a calculated value, while the others were measured values.

All birds were kept in an environmentally controlled poultry house with windows. Fifteen stainless steel cages (100 cm length × 60 cm width × 50 cm height) with wire-net floor were used. The initial temperature of the room was set at 32 °C and it was reduced by 2 or 3 °C weekly until it reached 22 °C, after which it was kept constant up to the end of the experiment. The relative humidity in the room was kept at 60%–75% throughout the trail period. The lighting schedule was set as 24 h of lighting on during d 1–3, and 16 h of lighting: 8 h of darkness up to d 14, then for natural light (about 14 h of lighting) until d 42. All birds had free access to water and feed and were inoculated with Newcastle disease infectious bronchitis vaccine and infectious bursal disease vaccine on d 7 and 21.

Carcase traits and sample collection

The carcase traits were measured in line with the method of Xie et al. (2021). Briefly, at d 42, one bird was randomly selected from each replicate (n = 5), fasted for 12 h, duly weighed (live weight), euthanized by electrical stunning and then immediately bled. After defeathering via scalding in a 65–70 °C water 30–60 s, the carcase weight was measured. Heads, feet and organs (except the lungs and kidneys) were subsequently removed, then eviscerated weight were determined. The carcase percentage and eviscerated percentage were then expressed as a percentage of live weight. The abdominal fat, breast muscles (Pectoralis major and minor muscle) and leg muscles (thigh and drumstick muscle) were removed and weighted. The breast muscle yield and leg muscle yield were calculated as a percentage of eviscerated weight. The abdominal fat yield was expressed as a percentage of eviscerated weight plus abdominal fat weight.

After being weighed, the left side of the Pectoralis major (PA) muscle were collected to measure the pH (pH_45 min and pH_24 h), water loss rate, drip loss, cooking loss, meat colour as well as shear force. In addition, about 100 g of PA muscle sample were immediately frozen and stored at −20 °C for determining muscle chemical composition, while another sample of PA muscles was immediately snap frozen in liquid nitrogen and stored at −80 °C for analysing the amino acids composition, the fatty acids composition and antioxidant capacity. Finally, another sample was stored at 4 °C for meat lipid oxidation by thiobarbituric acid reactive substance (TBARS) analysis.

Meat quality

At 45 min and 24 h post-mortem, the pH value of three different locations within the medial surface (bone side) of the PA muscle was measured using a portable pH metre (Instruments, Wilmington, MA, USA) with a puncture electrode (Otto et al. 2004). Prior to the measurement the pH metre was calibrated with 2 pH standard solutions (pH 7.0 and pH 4.0).

Meat colour attributes, including lightness (L*), redness (a*) and yellowness (b*), were measured (average value of three measurements was taken from the middle and two corners of the PA muscle samples) using Minolta CR-400 Chroma metre (Minolta, Tokyo, Japan). The machine was programmed to use a D65 illuminant, a 2° observer with an 8 mm aperture and calibrated with a white tile (L* = 92.30, a* = 0.32 and b* = 0.33).

The measurements of water loss rate were conducted as described by Farouk et al. (2004). A PA muscle sample (1.0 cm in diameter and 0.5 cm in thickness) was taken. The samples were then weighed and wrapped in an 8-layer filter paper. Subsequently, they were pressed using a compression machine (YYW-2, Nanjing Soil Instrument, Nanjing, China) at a force of 35 kg for 5 min and then reweighed, water loss rate was calculated as a percentage weight lost by the sample.

Drip loss was measured as described by Zhang et al. (2021). Approximately 5 g of the left PA muscle was suspended in a sealed plastic case and left at 4 °C for 24 h. Then, the surface moisture of the sample was absorbed with filter paper and the sample was re-weighed. The drip loss was determined as a percentage of the weight lost by the sample during the refrigerated storage period.

The measurements of cooking loss were conducted as described by Petracci and Baéza (2011). The PA muscle samples were heated in a water bath at 80 °C for 20 min. The samples were then dried using paper towel and weighed again, and the cooking loss was calculated as a percentage weight lost by the sample. After cooking, the samples were used to determine shear force according to Dalle Zotte et al. (2017). The muscles were cut into 1 cm × 1 cm × 2.5 cm along the direction of the muscle fibres. The strips were sheared perpendicular to the muscle fibre using a texture analyser (C-LM2, Xieli Technology Development Co., LTD, Qinhuangdao, China). Each muscle sample was measured three times, and the average value was taken as the shear force of the samples.

Muscle chemical composition

Chemical composition of the PA sample was analysed according to the AOAC (2000) methods. The moisture content was measured based on oven drying 2 g of fresh samples at 105 °C for 24 h. Subsequently, crude protein (nitrogen × 6.25) and crude fat content of de-moist samples were estimated using the standard Kjeldahl and Soxhlet methods, respectively. Ash content was determined by incinerating the sample in a muffle furnace at 550 °C for 6 h. The content of moisture, crude protein, ether extract and ash was expressed as a percentage of fresh muscle weight.

Fatty acid composition

About 80–100 mg PA muscle sample was homogenised and mixed with 3 mL of n-hexane and 100 μL of the internal standard (methyl nonadecylate, Sigma Chemicals, St. Louis, MO, USA). The mixture was shaken and heated at 50 °C for 30 min. Then, 3 mL of KOH/CH₃OH (0.4 mol/L) was added. The mixture was homogenised with a vortex mixer, heated for 30 min at 85 °C and then cooled for 6–7 min. Then, 3 mL of trifluoro(methanol)boron was added. The mixture was then shaken and reheated for 30 min at 85 °C. After cooling to ambient temperature, the upper extraction layer (n-hexane) was collected. A gas chromatography-mass spectrometer (GC–MS 7890B 5977 A, Agilent, USA) with DB-23 (30 m × 320 um × 0.25 um) column was used. The column temperature distribution was as follows: maintained at 50 °C for 1 min, increased to 175 °C at a rate of 25 °C/min, increased to 230 °C at a rate of 4 °C/min and the total analysis time is 24.75 min. Helium was used as the carrier gas. The shunt ratio and injection volume were 1/5 and 1 μL, respectively. The injector and detector temperatures were set as 250 °C and 230 °C, respectively. The concentrations of individual fatty acids were quantified according to the peak area and indicated as % total fatty acid.

Amino acid composition

Approximately 50 mg of dried PA muscle sample was weighted into a glass bottle and 15 mL HCl (6 mol/L) was added. After filling with nitrogen, the mixture was hydrolysed at 110 ± 1 °C for 24 h. The hydrolysate was transferred into 25 mL volumetric flask and diluted to calibration tail with ultrapure water. The diluent (0.5 mL) was transferred into 1.5 mL microcentrifuge tube, dried under vacuum at 60 °C, washed twice with 200 μL ultrapure water and then redissolved with 2.5 mL HCl (0.02 mol/L). Subsequently, the solvent was filtered using a 0.25 μm membrane filter into an autosampler vial before amino acid analysis with an L-8900 amino acid analyser (HITACHI, Japan). The individual amino acids contents were quantified based on peak area and expressed as a proportion of total amino acid. The total essential amino acid (EAA) was considered as sum of arginine (Arg), histidine, isoleucine, leucine, lysine, methionine (Met), phenylalanine, threonine and valine, and the total nonessential amino acid (NEAA) was sum of alanine (Ala), aspartic acid (Asp), cystine, glutamine (Gln), glycine (Gly), serine and tyrosine (Liu et al. 2015). The flavour amino acid (FAA) was calculated as sum of Asp, Gln, Gly, Ala, Met and Arg.

Antioxidant enzyme activities and GSH content

The activities of total superoxide dismutase (T-SOD) and GSH-Px, CAT and the concentration of glutathione (GSH) in PA muscle tissues were measured using commercial assay kits (Nanjing Jiancheng Bioengineering Institute, Nanjing, China) according to the manufacturer’s instructions.

Lipid oxidation

The PA muscle samples were packaged in ziploc plastic bags and stored in the refrigerator at 4 °C for 1, 3, 5 and 7 days of storage. Then the subsamples were taken and kept at −80 °C until analysis. The lipid oxidation was determined by TBARS assay kits (Beijing Dakemei Technology Co. Ltd, China) according to the manufacturer’s specifications. The TBARS values were expressed as μmol of malondialdehyde per g protein of tissue.

Statistical analysis

Data were tested for normality using the UNIVARIATE procedure of the SAS 9.2 (SAS Institute, Gary, NC). All the data were presented as the arithmetic mean and standard error of the mean (SEM) (for all groups together). Each broiler was treated as the experimental unit. Analysis of variance (ANOVA) was performed using a general linear model (GLM). The statistical model used for the analysis was Y_ij = μ + A_i + E_ij, where Y_ij is the dependent variable; μ is the overall mean; A_i is the effect of the level of dandelion (range = 1–3); and E_ij is the random effect. The differences among treatments were tested using LSD multiple comparisons. Polynomial analysis was conducted to determine the linear or quadratic response to increasing dandelion dosage in the diet. Differences were considered to be statistically significant at p ≤ 0.05, with trends defined as 0.05 < p < 0.10.

Results

Carcase traits

The carcase percentage, breast muscle yield and leg muscle yield of broilers were not affected by adding dandelion (Table 2). Compared with LD group, the eviscerated percentage of HD group tended to be higher (p = 0.090). The abdominal fat yield of HD group tended to be lower than that of CON group (p = 0.078). Moreover, eviscerated percentage showed a quadratic response due to supplemental levels of dandelion.

Table 2. Effects of dandelion on the carcase traits of broilers.

Item	CON	LD	HD	SEM	p-value
					Treatment	Linear	Quadratic
Carcase percentage, %	95.1	95.26	93.84	0.354	0.296	0.567	0.334
Eviscerated percentage, %	74.35^xy	71.35^y	78.56^x	1.118	0.090	0.175	0.081
Breast muscle yield, %	28.57	27.58	29.13	0.379	0.474	0.319	0.256
Leg muscle yield, %	20.11	21.12	19.71	0.287	0.201	0.132	0.088
Abdominal fat yield, %	2.92^x	2.31^xy	2.05^y	0.118	0.078	0.187	0.508

CON: the control group fed basal diet (n = 5); LD: basal diet supplemented with 0.5 g/kg of dandelion (n = 5); HD: basal diet supplemented with 1.0 g/kg of dandelion (n = 5).

SEM: standard error of means.

^xyMeans in the same row without common superscript letter tended to be different (p < 0.10).

Meat quality

Dietary dandelion supplementation had no influences on pH_45 min, pH_24 h, L*, b*, drip loss and shear force of PA muscle (Table 3). Compared with CON group, the LD group had higher a* (p = 0.083), but lower cooking loss (p = 0.024). It was worth noticing that the water loss rate of HD group was higher than CON and LD groups (p < 0.01). With increasing supplemental dandelion levels, the a* increased linearly and quadratically (p < 0.05). The water loss rate increased quadratically as dietary dandelion increased (p < 0.05). Meanwhile, the cooking loss showed a linear and quadratic response as dietary dandelion increased (p < 0.05).

Table 3. Effects of dandelion on the meat quality of broilers.

Item	CON	LD	HD	SEM	p-value
					Treatment	Linear	Quadratic
pH45 min	6.56	6.32	6.36	0.056	0.164	0.116	0.217
pH24 h	6.03	6.00	6.04	0.034	0.887	0.657	0.632
Lightness (L*)	47.35	46.42	47.50	0.418	0.347	0.180	0.154
Redness (a*)	2.55^y	3.25^x	2.82^xy	0.123	0.083	0.033	0.047
Yellowness (b*)	10.41	10.14	10.44	0.226	0.847	0.593	0.576
Water loss rate, %	15.89^b	16.40^b	23.34^a	1.076	<0.01	0.152	<0.01
Drip loss, %	2.91	2.75	2.60	0.116	0.740	0.795	0.981
Cooking loss, %	32.28^a	29.18^b	33.18^a	0.515	0.024	0.013	<0.01
Shear force, %	56.26	62.94	70.61	3.102	0.254	0.656	0.942

CON: the control group fed basal diet (n = 5); LD: basal diet supplemented with 0.5 g/kg of dandelion (n = 5); HD: basal diet supplemented with 1.0 g/kg of dandelion (n = 5).

SEM: standard error of means.

^abMeans in the same row without common superscript letter differ significantly (p < 0.05).

^xyMeans in the same row without common superscript letter tended to be different (p < 0.10)

Muscle chemical composition

With regard to muscle chemical composition, there were no effects of dandelion supplementation on muscle moisture, ether extract or ash contents (Table 4). Compared with CON group, the muscle crude protein content was reduced in the LD and HD groups (p = 0.016). The muscle crude protein content had a linear decrease trend with increasing dandelion levels (p = 0.057).

Table 4. Effects of dandelion on the muscle chemical composition of broilers.

Item	CON	LD	HD	SEM	p-value
					Treatment	Linear	Quadratic
Moisture, %	75.14	75.40	75.56	0.142	0.493	0.621	0.862
Crude protein, %	23.77^a	22.93^b	22.79^b	0.160	0.016	0.057	0.227
Ether extract, %	0.55	0.63	0.60	0.017	0.113	0.053	0.093
Ash, %	1.58	1.54	1.57	0.029	0.878	0.620	0.620

CON: the control group fed basal diet (n = 5); LD: basal diet supplemented with 0.5 g/kg of dandelion (n = 5); HD: basal diet supplemented with 1.0 g/kg of dandelion (n = 5).

SEM: standard error of means.

^abMeans in the same row without common superscript letter differ significantly (p < 0.05).

Fatty acid composition

The fatty acid composition of PA muscle is shown in Table 5. Dietary dandelion supplementation at 0.5 g/kg increased (p < 0.01) the proportion of C20:2 and C20:4n-6 and sum of n-3 PUFA of the PA muscles in comparison with the CON group. The C22:6n-3 in LD group tended to be higher than that in HD group (p = 0.078). Increasing levels of dandelion increased the proportion of C20:2 and C20:4n-6 as well as the sum of n-3 PUFA in a linear and quadratic manner (p < 0.05). In addition, the proportion of C22:6n-3 had linear increase trend (p = 0.051) and quadratic increase (p = 0.038).

Table 5. Effects of dandelion on pectoralis major muscle fatty acid composition (% of total fatty acid) of broilers.

Item	CON	LD	HD	SEM	p-value
					Treatment	Linear	Quadratic
C16:0	24.88	24.58	24.18	1.206	0.628	0.950	0.940
C18:0	13.06	15.85	13.07	2.771	0.152	0.065	0.059
C20:0	0.07	0.08	0.07	0.010	0.248	0.100	0.104
C22:0	0.02	0.03	0.02	0.004	0.562	0.878	1.000
C24:0	0.38	0.52	0.29	0.195	0.126	0.086	0.066
C16:1	1.19	0.90	1.32	0.472	0.316	0.202	0.170
C20:1	0.23	0.21	0.24	0.047	0.746	0.497	0.472
C18:1n-9	28.35	23.32	28.51	4.710	0.128	0.051	0.047
C20:2	1.12^y	1.74^x	1.04^y	0.141	0.051	0.021	0.017
C18:2n-6	22.22	22.30	23.63	0.563	0.436	0.676	0.557
C18:3n-6	0.97	1.26	0.79	0.400	0.113	0.072	0.055
C18:3n-3	1.36	1.45	1.32	0.165	0.417	0.238	0.213
C20:3n-6	1.06	1.20	0.84	0.430	0.402	0.349	0.292
C20:4n-6	4.28b	7.23^a	3.57^b	2.093	<0.01	<0.01	<0.01
C22:6n-3	0.54^xy	0.74^x	0.41^y	0.255	0.078	0.051	0.038
SFA	39.11	41.04	37.64	1.039	0.211	0.142	0.114
UFA	60.89	58.96	62.36	0.976	0.211	0.142	0.114
MUFA	28.26	22.98	30.07	0.940	0.132	0.065	0.054
PUFA	32.63	35.97	32.29	1.011	0.119	0.047	0.043
n-6 PUFA	29.41	32.05	29.52	0.997	0.141	0.053	0.052
n-3 PUFA	1.75^b	2.19^a	1.74^b	1.004	0.029	0.010	<0.01
n-6/n-3	15.94	14.80	17.13	0.931	0.113	0.101	0.072

CON: the control group fed basal diet (n = 5); LD: basal diet supplemented with 0.5 g/kg of dandelion (n = 5); HD: basal diet supplemented with 1.0 g/kg of dandelion (n = 5).

SEM: standard error of means. SFA: saturated fatty acids; UFA: unsaturated fatty acid; MUFA: monounsaturated fatty acids; PUFA: polyunsaturated fatty acids.

^abMeans in the same row without common superscript letter differ significantly (p < 0.05).

^xyMeans in the same row without common superscript letter tended to be different (p < 0.10).

Amino acid composition

As shown in Table 6, the proportion of Arg tended to be reduced in HD group compared to CON (p = 0.084). However, the proportions of the other amino acids were not affected by dandelion supplementation.

Table 6. Effects of dandelion on pectoralis major muscle amino acid composition of broilers (%).

Item	CON	LD	HD	SEM	p-value
					Treatment	Linear	Quadratic
Asparagic acid (Asp)	10.42	10.44	10.71	0.091	0.363	0.783	0.513
Threonine (Thr)	5.71	5.63	5.49	0.056	0.299	0.846	0.802
Serine (Ser)	5.35	5.35	5.33	0.026	0.971	0.947	1.000
Glutamic acid (Glu)	12.91	12.83	12.62	0.080	0.326	0.961	0.707
Glycine (Gly)	8.58	8.66	8.69	0.066	0.799	0.735	0.866
Alanine (Ala)	9.06	8.94	8.74	0.077	0.242	0.827	0.789
Cysteine (Cys)	0.44	0.44	0.41	0.016	0.692	1.000	0.813
Valine (Val)	5.21	5.26	5.33	0.042	0.531	0.827	0.922
Methionine (Met)	2.72	2.63	2.54	0.040	0.169	0.607	0.976
Isoleucine (Ile)	5.07	5.15	5.18	0.030	0.407	0.502	0.747
Leucine (Leu)	8.98	8.88	8.77	0.044	0.146	0.601	0.963
Tyrosine (Tyr)	2.62	2.58	2.56	0.021	0.575	0.557	0.745
Phenylalanine (Phe)	4.50	4.55	4.67	0.046	0.328	0.948	0.720
Lysine (Lys)	9.03	9.23	9.36	0.086	0.308	0.544	0.853
Histidine (His)	4.08	4.18	4.37	0.069	0.227	0.854	0.754
Arginine (Arg)	5.31^x	5.27^xy	5.23^y	0.014	0.084	0.476	0.952
EAA	50.61	50.77	50.93	0.091	0.383	0.679	0.980
NEAA	49.39	49.23	49.07	0.091	0.383	0.679	0.980
FAA	49.00	48.77	48.53	0.116	0.259	0.649	0.989

CON: the control group fed basal diet (n = 5); LD: basal diet supplemented with 0.5 g/kg of dandelion (n = 5); HD: basal diet supplemented with 1.0 g/kg of dandelion (n = 5).

SEM: standard error of means. EAA; essential amino acid; NEAA; non-essential amino acid; FAA; flavour amino acid.

^xyMeans in the same row without common superscript letter tended to be different (p < 0.10).

Antioxidant enzyme activities and GSH content

The effects of dandelion supplementation on the antioxidant enzyme activities and GSH content of breast muscles are shown in Table 7. No differences were observed for the activities of CAT, T-SOD and GSH-Px, as well as GSH concentration.

Table 7. Effects of dandelion on antioxidant enzyme activities and GSH content of pectoralis major muscle of broilers.

Item	CON	LD	HD	SEM	p-value
					Treatment	Linear	Quadratic
CAT (U/mg protein)	14.65	17.91	16.41	1.060	0.486	0.253	0.309
GSH-Px (U/mg protein)	11.53	12.96	13.54	0.655	0.459	0.529	0.770
T-SOD (U/mg protein)	688.68	599.94	635.35	19.334	0.172	0.084	0.130
GSH (μmol/g protein)	164.64	149.79	157.92	5.718	0.654	0.373	0.407

CON: the control group fed basal diet (n = 5); LD: basal diet supplemented with 0.5 g/kg of dandelion (n = 5); HD: basal diet supplemented with 1.0 g/kg of dandelion (n = 5).

SEM: standard error of means; CAT: catalase; GSH-Px: glutathione peroxidase; T-SOD: total of superoxide dismutase; GSH: glutathione.

Lipid oxidation

No significant changes were found for TBARS value on d 1 among the CON and dandelion supplementation groups (Table 8). Compared with the CON group, dietary dandelion supplementation at 0.5 and 1.0 g/kg decreased the TBARS value on d 3 and d 5 (p < 0.05). On d 7, HD group had significantly lower TBARS value than CON group (p < 0.05). There was a linear and quadratic decrease in TBARS value on d 3 along with a linear decrease in TBARS value on d 5 (p < 0.05).

Table 8. Effects of dandelion on thiobarbituric acid reactive substance (TBARS) of pectoralis major muscle during storage.

Item	CON	LD	HD	SEM	p-value
					Treatment	Linear	Quadratic
1 day	2.15	1.71	1.48	0.137	0.122	0.349	0.695
3 days	2.55^a	1.29^b	1.46^b	0.192	<0.01	<0.01	0.011
5 days	2.37^a	1.59^b	1.62^b	0.153	0.029	0.034	0.112
7 days	2.40^a	2.00^ab	1.47^b	0.150	0.045	0.526	0.794

CON: the control group fed basal diet (n = 5); LD: basal diet supplemented with 0.5 g/kg of dandelion (n = 5); HD: basal diet supplemented with 1.0 g/kg of dandelion (n = 5).

SEM: standard error of means.

TBARS expressed as μmol of malondialdehyde per g protein of tissue.

^abMeans in the same row without common superscript letter differ significantly (p < 0.05).

Discussion

Previous studies have investigated dandelion and its bioactive molecules, such as polysaccharides, polyphenol and flavonoids, for the growth promoting and various biological effects (You et al. 2010; Yan et al. 2012; Aremu et al. 2019), of which antioxidant capacity may be pertinent to improving meat quality. In previously study, we have confirmed that broilers fed with 0.5 g/kg dandelion had decreased feed to gain ratio (Mao et al. 2022). In this study, the effects of dietary dandelion supplementation on carcase traits, meat quality and antioxidant capacity of broilers were investigated.

There are only a few literature reports on the effect of dandelion on carcase traits in broilers. Al-Kassi and Witwit (2009) found that inclusion of dandelion (0.25% and 0.5%) did not affect the dressing percentage. In another study conducted by Qureshi et al. (2015), dietary supplementation of 0.5% dandelion leaves had no significant effect on dressing percentage and breast, drumsticks and thighs yield of meat type chicken. In this study, our data showed that there was no significant difference in carcase percentage, breast muscle yield and leg muscle yield of broilers. Although there was a quadratic response tendency for eviscerated percentage to dandelion supplementation level, broilers fed 0.5 and 1.0 g/kg dandelion had similar eviscerated percentage than CON group, indicating that dietary dandelion supplementation did not improve or compromise the carcase yield of broiler chickens. Excessive abdominal fat deposition is one of the major problems in broiler production. In the present study, supplementation with 1.0 g/kg dandelion tended to decrease abdominal fat yield. Similarly, Deng et al. (2012) found that the abdominal fat yield of broilers was decreased by alfalfa extract rich in polysaccharides, triterpenoid saponins and flavonoids. The modifying effects of dandelion on abdominal fat yield might be due to polyphenol and flavonoids, which intensified bile secretion (Singh et al. 2008).

Generally, meat quality should be reflected by several indexes, such as pH, meat colour, water holding capacity and shear force. It has been proven that the bioactive ingredients of herbal additives exhibit great antioxidative capacity and could delay glycolysis and oxymyoglobin oxidation and reduce oxidative-induced conformational alterations and fragmentation of myofibrillar proteins (Xie et al. 2021; Salami et al. 2015). Consistent with previous study in pigs (Yan et al. 2011), there were no significant differences between the pH values recorded in this experiment. The colour is an important meat quality index and good colour and lustre can often stimulate consumers’ desire to buy. Drip loss, cooking loss, and water loss rate are indicators to measure the water holding capacity of PA muscle in broilers. In this study, there was quadratic response of a* (redness), cooking loss and water loss rate of PA muscle with incremental dietary dandelion levels. Increased tendency in a* and significant decrease in cooking loss were noted with 0.5 g/kg dandelion in the diet, while 1.0 g/kg dandelion did not lead to further influence on a* and cooking loss. Furthermore, we found that the inclusion of dandelion at 1.0 g/kg significantly increased water loss rate of PA muscle, which indicates a reduction of meat water holding capacity. It is possible that excessive intake of bioactive components from dandelion may resulted in toxic effects and stress, even though they are beneficial in low amounts (Tan et al. 2017; Giri et al. 2022). Thereby the meat quality data indicate that the inclusion of 0.5 g/kg dandelion should be recommended.

In the current study, crude protein level of PA muscle responded to level of dandelion in a linear manner. Supplementation of 0.5 and 1.0 g/kg dandelion significantly decreased crude protein level in PA muscle of broilers. Likewise, Kasapidou et al. (2014) reported a significant linear decrease in breast muscle protein content due to herbs Melissa officinalis supplementation. Similar results found by Starčević et al. (2015) suggested that broilers receiving the tannic acid, a natural phenolic compound, had lower protein in breast muscle. In contrast, Mohammed (2018) showed that supplementation with herbs increased muscle protein content of broilers. The discrepancy in the crude protein level of meat might be caused by the rearing environment, herbs kinds, preparation and procession methods and diet.

Chicken meat is a good source of essential fatty acid and amino acid for humans (Pereira and Vicente 2013). A higher proportion of PUFAs in meat was desired by consumers, because PUFAs are considered as functional ingredients to prevent coronary heart disease and other chronic diseases (Russo 2009). Many studies have reported a possibility of modifying the fatty acid profile in meat with the use of herbal additives (Valenzuela-Grijalva et al. 2017). For example, fresh cut nettle (Dukić-Stojčić et al. 2016) and turmeric (Galli et al. 2020) increased the proportion of PUFAs, including n-3 or n-6 PUFAs, while decreased the ratio n-6/n-3 in chicken products. However, the utilisation of herb additives in practice was highly inconsistent, since the quality of herbs product differed in differ greatly due to the different herbal materials and dosage and forms their administration (Redoy et al. 2021; Shirani et al. 2019). In the studies of Forte et al. (2018), a water-based extract of oregano (150 mg/kg feed) did not influence the percentage of fatty acids in breast meat of broiler chickens. Furthermore, Sohaib et al. (2015) demonstrated that UFA synthesis of broilers decreased along with an increase in the level of quercetin and α-tocopherol. In our findings, the proportion of C20:2, C20:4n-6 and C22:6n-3 as well as sum of n-3 PUFA in PA muscle responded to graded level of dandelion in quadratic manner. These fatty acids were higher in broilers with 0.5 g/kg dandelion, while not in broilers with 1.0 g/kg dandelion. Moreover, the only change in amino acid composition PA muscle observed in the present study was a decreased tendency of arginine when 1.0 g/kg dandelion was fed to the broilers. This is due to the fact that administration of excessive amount of dandelion might have a negative effect on antioxidative response of host (Tan et al. 2017; Giri et al. 2022).

Lipid peroxidation induced by high levels of free radicals is a primary cause of deterioration of meat (Domínguez et al. 2019). The strong free radicals scavenging activity of bioactive ingredients in dandelion has been well demonstrated (Huang and Gu 2016; Cai et al. 2019). However, the present study provided the first evidence in broilers that dietary dandelion supplementation had no direct effect on the activities of CAT, T-SOD and GSH-Px as well as GSH concentration in the breast muscle. Inside the muscle, both the enzymatic antioxidant (CAT, SOD, GSH-Px) and non-enzymatic (GSH, vitamins, peptides) are responsible for removing ROS and reducing lipid peroxidation. Therefore, the inhibitory effects of dandelion on lipid peroxidation may not depend on antioxidant enzymes and GSH, and further study is required.

Poultry meat is highly sensitive to oxidative processes owing to the high degree of muscle lipids unsaturation (Estévez 2015). It is well known that dietary supplementation with natural antioxidants such as polyphenols, flavonoids and polysaccharides can improve meat oxidative stability of broilers (Fellenberg and Speisky 2006). TBARS assay is one of the most widely used methods for determining the lipid oxidative stability. There is evidence that aqueous extracts from dandelion root decreased lipid oxidation in rats (Aremu et al. 2019). In addition, Majewski et al. (2020) suggested that dandelion exerted a protective effect on lipid oxidation, as measured by the level of decreased TBARS in the spleen, brain and thoracic arteries in the rats. Consistent with previous findings, dandelion supplementation decreased TBARS value of PA muscle during storage for 3 and 5 days linearly and quadratically, which were lower in 0.5 g/kg dandelion group. The results thus confirm that dandelion (0.5 g/kg) could effectively protect broiler breast muscles against lipid oxidation without modifying the antioxidant enzymes activities and GSH content.

Conclusions

Supplemental dandelion increased the a* value, decreased the cooking loss, elevated the proportion of PUFAs and enhanced lipid oxidative stability of PA muscle. The beneficial effect of 0.5 g/kg of dandelion was superior, and 0.5 g/kg could be a suitable concentration for dandelion supplementation in broilers. Dandelion could be a potential dietary antioxidant supplement in the poultry industry, which enhanced some quality traits and lipid oxidative stability of chicken meat.

Ethical approval

All experimental procedures were approved by the Animal Care and Use Committee of Inner Mongolia Agricultural University with the permission number of (2020) 065.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The results and analyses presented in this article are freely available upon request.

Additional information

Funding

This research was funded by Major Science and Technology Program of Inner Mongolia Autonomous Region [2021ZD0024-4, 2021ZD0023-3, 2020ZD0004] and Key Technology Project of Inner Mongolia Autonomous Region [2020GG0030].