Effect of dietary supplementation with flavonoid from Scutellaria baicalensis Georgi on growth performance, meat quality and antioxidative ability of broilers

LlAO Xiu-dong, WEN Qian, ZHANG Ling-yan, LU Lin, ZHANG Li-yang, LUO Xu-gang

Mineral Nutrition Research Division, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193,P.R.China

1. lntroduction

Flavonoids (FNs) from plants have several biological properties, such as antioxidant, anti-in flammatory and antibacterial protective effects on cells and organs of animals(Liang and Han 2003; Zhanget al.2011). Numerous studies have shown that FNs have beneficial effects on performance of animals (Jenkins and Atwal 1995; Payneet al.2001;Jianget al.2007).

It has been reported that dietary supplementation with theFN fromScutellaria baicalensisGeorgi (SBGFN) could improve growth performance, immune function and intestinal health of broilers (Mouet al.2010; Lianget al.2012). TheS. baicalensisGeorgi (SBG) is a kind of traditional Chinese medicine, whose main effective component is FN. The FN has a special structure which can chelate with metal ions like zinc (Zn). As an essential trace element for animals,Zn can promote growth and development, raise the power of immunity system and maintain the cell membrane’s integrity of animals (Liang 2006). Wanget al.(2004)found that Zn chelate with baicalin was more effective than baicalin in inhibiting the activity of HIV-1 entry into host cells.When chelated with Zn, baicalin has a lower cytotoxicity compared with baicalin itselfin vitro, and behaves more effective on scavenging free radicals and protecting the red cell membranes from oxidative damage. It is also reported that Zn chelate with baicalin had anti-in flammatory and anti-allergic efficiencies in mice (Jiaet al.1994). We hypothesized that SBGFN might be more effective for animals when it is chelated with Zn. The SBGFN-Zn as one new product might have a good application prospect in improving performances of animals. However, to our knowledge, the information is lacking on the effect of SBGFN-Zn on performances of broilers and other animals.Therefore, the present study was conducted to investigate the effect of dietary supplementation with SBGFN as SBGFN-Zn on growth performance, carcass characteristics,meat quality, immune function and antioxidation of broilers.

2. Materials and methods

2.1. Experimental design and treatments

A completely randomized design was used in this study.There were a total of 5 dietary treatments, including a SBGFN-unsupplemented corn-soybean meal basal diet(control) or the basal diet supplemented with 60, 120, 180 or 240 mg SBGFN kg–1in the form of SBGFN-Zn, respectively.

2.2. Animals

All experimental procedures were approved by the Animal Management Committee (in charge of animal welfare issue) of the Institute of Animal Science, Chinese Academy of Agricultural Sciences (IAS-CAAS, Beijing, China) and performed in accordance with the guidelines. Ethical approval on animal survival was given by the Animal Ethics Committee of IAS-CAAS. A total of 450 one-d-old Arbor Acres commercial male broiler chicks (Huadu Broiler Company, Beijing, China) were randomly assigned into 5 treatments with 6 replicate cages each with 15 birds per cage based upon body weight for 42 d. Broilers were maintained on a 24-h constant light schedule. Feeding management throughout the experiment followed the Arbor Acres broilers management guidelines. Feed and tap water were availablead libitum. Broilers were vaccinated with the Newcastle vaccine VA/GA at 7 and 24 d of age, and the H5N1 vaccine at 11 and 28 d of age, respectively. These vaccines were purchased from Harbin Veterinary Research Institute,Chinese Academy of Agricultural Sciences. The numbers of dead broilers were recorded daily, and feed intake and weight gain of broilers per cage were measured at 21 and 42 d of age to calculate the average daily gain (ADG),average daily feed intake (ADFI), feed:gain ratio (F/G) and mortality.

2.3. Diets

The corn-soybean meal basal diets (Table 1) were formulated to meet or exceed the National Research Council(NRC 1994) requirements for broilers for all nutrients.The SBGFN-Zn (containing 85% SBGFN and 6.25% Zn,respectively; Beijing Huamuweiye Technology Co., Ltd.,China) was added to the basal diet according to the above experimental treatments. The SBGFN was isolated from SBG. Each treatment diet was supplemented with 60 or 40 mg of Zn kg–1of diet for broilers from 1 to 21 or 22 to 42 d of age by adjusting the usage of corn starch and Znsulfate according to the Zn content from added SBGFN-Zn,respectively. Each supplemental SBGFN level was mixed with corn-starch to the same weight and then mixed with each aliquot of the basal diet. The diets were fed in mash form.

Table 1 Composition and nutrient levels of the basal diets for broilers (as-fed basis)

2.4. Sample collections and preparations

The samples of feed ingredients and diets from all the treatments were taken and submitted for analyses of crude protein (CP), calcium (Ca) and Zn before the initiation of the trial to con firm CP, Ca and Zn contents in diets. At 21 and 42 d of age, birds were individually weighed following an 12-h fast and 2 birds from each replicate cage were chosen based on average body weight (BW). Whole blood samples were taken into heparinized tubes from each of two birdsviaa wing vein for lymphocyte proliferation analysis. Another blood sample was also collected into tubes without anticoagulant, and then was centrifuged at 3 000×g for 10 min at 4°C to harvest serum samples for analyses of antibody titers against Newcastle and H5N1 vaccines, malondialdehyde (MDA) concentration as well as of total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) activity. At 42 d of age, the birds were slaughtered by cervical dislocation. The breast and thigh muscles were used to determine the meat color and the pH value after slaughter, and then they were placed in a plastic bag and stored at 4°C for 24 h to determine the drip loss of the muscle, and then cooked to determine the shear force of the muscle, respectively. The percentages of spleen and thymus were calculated by using their weights to divide the live BW. The liver and right breast muscle were subsequently taken out and then frozen at –20°C for analyses of liver and breast muscle MDA concentration as well as T-SOD and GSH-Px activity. All samples from 2 birds in each replicate were pooled into one sample in equal ratios before analysis.

2.5. Sample analyses

The contents of Zn and Ca in feed ingredients and diet samples were measured by inductively coupled plasma emission spectroscope (model IRIS Intrepid II, Thermal Jarrell Ash, Waltham, MA, USA) after wet digestions with HNO3and HCIO4as described by Luoet al.(2007).Concentrations of CP in feed ingredient or diet samples were determined using Official Analytical Chemists methods(AOAC 1990). The pH values of breast and thigh muscles were tested immediately after the birds were slaughtered using a Model pH-211 meter (Hanna Instruments Inc.,Padova, Italy) equipped with a spear electrode. The meat color (L＊, a＊ and b＊) was determined using an automatic colorimeter (model SC-80C; Beijing Kangguang Instrument Co., Beijing, China). The meat color was measured at 3 points of every meat after slaughter. The breast muscle and thigh muscle were excised (1 cm×1 cm×5 cm) and weighed and then placed in a plastic bag and stored at 4°C.After 24 h, the muscle was removed from the plastic bag wiped with filter paper, and weighed to evaluate drip loss and expressed as a percentage of initial muscle weight.At 24 h after slaughter, the breast and thigh muscles were heated in plastic bags in a water bath at 80 to 85°C until the temperature of the meat center reached 75°C. They were then taken out and cooled to room temperature and excised(1 cm×1 cm×5 cm) to measure the shear force at 3 points of every meat with a C-LM Muscle Tenderness Instrument(Northeast Agricultural University, Heilongjiang, China). The concentration of MDA, activity of T-SOD and GSH-Px in serum, liver and muscle samples of broilers were determined using the detection kits of MDA, T-SOD and GSH-Px (Nanjing Jiancheng Bioengineering Institute, Nanjing, China). The antibody titers against Newcastle and H5N1 vaccines were measured using the haemagglut-ination inhibition test as described by Meulemanset al.(1987). The analysis of whole blood T lymphocyte proliferation was carried out by MTT assay (Mosmann 1983). The mean optical density was determined for bipartite samples, and the proliferation responses were expressed as a mean stimulation index obtained by dividing the mean optical density (OD) of stimulated cells by OD of unstimulated cells (SI).

2.6. Statistical analyses

Data were analyzed using the general linear model procedure of the SAS Institute (release 9.2; SAS Inst.Inc., Cary, NC, USA). The replicate cage served as the experimental unit. Percentage data were transformed to arcsine for analysis. Differences among means were tested by the least significant difference method and theP＜0.05 was considered to be statistically significant.

3. Results

3.1. Growth performance

Supplemental SBGFN did not affect (P＞0.20) ADG (33.4, 79.9 and 58.8 g d–1), ADfi(46.1, 156 and 101 g d–1), F/G (1.38,1.95 and 1.72 g g–1) and mortality (1.56, 0.92 and 2.44%)of broilers during 1 to 21, 22 to 42 and 1 to 42 d of age,respectively (values represent the means of all treatments).

3.2. Meat quality

Supplemental SBGFN affected (P＜0.01) drip loss in thigh muscle, but did not affect (P＞0.05) L＊, a＊ and b＊ values, shear force and pH value in both breast and thigh muscles as well as drip loss in breast muscle of broilers (Table 2). Chicks fed the diets supplemented with 120, 180 and 240 mg SBGFN kg–1had lower (P＜0.03) drip loss of thigh muscle than those fed the control diet, whereas no difference (P＞0.06) in drip loss was found between the control chicks and those fed the diet supplemented with 60 mg SBGFN kg–1.

3.3. lmmune function

Supplemental SBGFN had no effect (P＞0.05) on the spleen(0.119) and thymus (0.452) percentages and serum antibody titers against H5N1 (7.73log2) at 42 d of age, against Newcastle (3.85 and 2.61log2) and blood T-lymphocyte proliferation (0.890 and 0.939 SI) of broilers at 21 and 42 d of age, respectively (values represent the means of all treatments).

3.4. Antioxidation

Supplemental SBGFN affected (P＜0.03) T-SOD and GSHPx activity in liver of broilers at 42 d of age, but did not affect(P＞0.11) MDA concentration either in liver or breast muscle,T-SOD and GSH-Px activity in breast muscle of broilers at 42 d of age as well as serum antioxidant parameters of broilers at 21 and 42 d of age (Tables 3 and 4). Broilers fed the diet supplemented with 180 mg SBGFN kg–1had higher (P＜0.03) liver T-SOD activity than those fed the diets supplemented with 0, 60 and 120 mg SBGFN kg–1with no differences (P＞0.27) between broilers fed the diets supplemented with 180 and 240 mg SBGFN kg–1. Broilers fed the diet supplemented with 180 mg SBGFN kg–1had higher (P＜0.02) liver GSH-Px activity than those fed the diets supplemented with all other levels of SBGFN, and no differences were observed between the control broilers and those fed the diets supplemented with 60, 120 or 240 mg SBGFN kg–1.

4. Discussion

Many studies have shown that FNs could promote the growth performance of broilers (Lianget al.2012; Maet al.2015). Lianget al.(2012) found that diets supplemented with skullcap flavone enhanced ADG and ADfiof broilers.Maet al.(2015) also reported that flavones of sea buckthorn fruits improved ADFI, ADG and final body weight of broilers.However, in the present study, we found that the diets supplemented with SBGFN as SBGFN-Zn did not influence the growth performance of broilers, which was similar to the reports of Kuhnet al.(2004) and Solcanet al.(2013).These differences might be due to different diets, type of chicks, growth phases, or different supplementation (Wang and Han 1994; Liet al.1999; Renet al.2001; Whitten and Patisaul 2001).

Table 2 Effect of dietary flavonoid from Scutellaria baicalensis Georgi (SBGFN) on meat quality of broilers at 42 d of age1)

Table 3 Effect of dietary flavonoid from Scutellaria baicalensis Georgi (SBGFN) on antioxidant parameters in serum of broilers1)

Table 4 Effect of dietary flavonoid from Scutellaria baicalensis Georgi (SBGFN) on antioxidant parameters in liver and breast muscle of broilers at 42 d of age1)

Drip loss was also an important index to evaluate meat quality (Ottoet al.2006). Moisture loss could take away the heme and cause the loss of soluble flavor substance in meat (Savageet al.1990; Lucianoet al.2009). Therefore,the moisture closely linked with the physical form, flavor and color of meat. The results from the present study showed that supplemental SBGFN-Zn decreased drip loss of thigh muscle, which was consistent with the study of Liet al.(2008), who found that flavones of sea buckthorn could decrease the drip loss in thigh muscle of broilers. The drip loss has been shown to be negatively related to antioxidant capability and immune function. The decreased drip loss may be due to increased antioxidative ability in the chickens or immunoregulatory effects of FNs through involvement of humoral immune components (Middleton 1996; Younget al.2003; Shenet al.2007). The exact mechanism remains unclear and needs to be further studied in the future.However, the results from the present study indicated that dietary supplementation with SBGFN as SBGFN-Zn had no effect on immune responses of broilers.

It has long been recognized that FNs have antioxidant activity, which have the ability to scavenge free radicals,superoxide and hydroxyl radicals by single-electron transfer(RiceEvanset al.1996; Choiet al.2002). The FNs could block apoptosis in human umbilical vein endothelial cells through decreasing reactive oxygen species, increasing glutathione and protecting DNA damage (Gonget al.2010).The results from our current study demonstrated that dietary supplementation of SBGFN in the form of SBGFN-Zn increased liver T-SOD and GSH-Px activity of broilers. The T-SOD and GSH-Px are important and widely existing freeradical scavenging enzymes in the body, and they can clear the superoxide and lipid hydroperoxide, reduce the damage of organic hydrogen peroxide to the body (Ma 2008). Fanget al.(1991) reported that FN-Zn could scavenge superoxide and inhibit membrane peroxidation of red blood cellin vitro.The above-mentioned previous results and those from the present study demonstrated that the FN-Zn chelate has strong antioxidant ability.

5. Conclusion

The results from the current study indicate that dietary supplementation with 120, 180 and 240 mg SBGFN kg–1as the SBGFN-Zn chelate improved meat quality, while the addition of 180 mg SBGFN kg–1promoted antioxidative ability of broilers. Therefore, the SBGFN-Zn as one new product might have a good application prospect in improving both meat quality and antioxidative ability of broilers.

Acknowledgements

This work was supported by the earmarked fund for China Agriculture Research System (CARS-41), and the Agricultural Science and Technology Innovation Program,China (ASTIP-IAS08).

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