Effects of Herba Picriae Extract on Growth Performance and Immune Organ Index of Guangxi Partridge Chickens

Cui YANG, Xiaoguang LIAO, Siqian WU, Huofu WAN, Jing SHI, Huihui CAO, Linling ZHAO, Dawei LAI, Fanquan ZENG, Fulin WANG, Jiahuang YANG, Zhuyue WU*

1. Animal Husbandry Research Institute of Guangxi Zhuang Autonomous Region, Nanning 530001, China; 2. Haid Feed Co., Ltd., Dongguan 523147, China

Abstract [Objectives ] The purpose of this experiment was to study the effects of dietary supplementation of Herba Picriae extract on the growth performance and immune organ index of Guangxi partridge chickens. [Methods ] A total of 500 one-day-old Guangxi partridge chickens were selected and randomly divided into five groups, five replicates for each group and 20 chickens for each replicate. Groups A, B and C were treatment groups, in which 0.70%, 0.35% and 0.175% of Herba Picriae extract was added to the basal diet, respectively. Group D was a positive drug control group, in which 0.01% colistin sulfate premix was supplemented. Group E was a blank control group, in which the chickens were fed the basal diet. The experimental period was 105 d. During the experiment, five chickens were randomly selected from each group on days 21, 35 and 49, respectively for the measurement of immune organ index. [Results ] When the chickens were fed basal diet supplemented with 0.175% of Herba Picriae extract, their daily body weight gain increased significantly from day 22 to day 35 and from day 71 to day 105 and tended to increase from day 1 to day 21, from day 36 to day 49, and from day 50 to day 70, with a range of 7.37%-8.72%. Dietary supplementation of 0.70% and 0.175% of Herba Picriae extract significantly promoted the growth and development of Fabricius bursae in the experimental chickens. [Conclusions ] Dietary supplementation of 0.175% of Herba Picriae extract improved the growth performance and feed intake, as well as 21-d-old bursal index of the experimental chickens.

Key words Herba Picriae extract, Guangxi partridge chicken, Growth performance, Immune organ index

1 Introduction

In the development of the chicken industry, the application of antibiotics has played an important role. In particular, those antibiotics that have a preventive effect on chicken diseases and can promote their growth are used in greater amounts. However, long-term large-scale use of antibiotics will lead to drug resistance, drug residues and environmental pollution, causing serious harm to human health. Some studies in recent years have shown that supplementing Fructus Ligustri Lucidi extract to the diet can improve the production performance and immune function of laying hens at the late peak laying period[1]; and supplementation of hesperidin preparation (150 mg/kg) to the diet of AA broilers and the supplementation of compound Chinese herbal medicine additive to the diet of Yunnan Wuding chicks can significantly improve the growth performance and enhance the immunity of the chickens[2-3]. This suggests that exploring replacement of antibiotics by Chinese herbs may be an effective way for the development of chicken industry. Herba Picriae is the dried whole grass ofPicriafel-tarraeLour, also known as Kucao, Shezongguan and Sihuansucao. It is bitter in taste and cold in nature, and has the functions of clearing away heat, detoxification, diminishing swelling and relieving pain[4]. It is one of the most distinctive Chinese herbal medicines in Guangxi. Modern pharmacological studies have shown that Herba Picriae has central sedative, analgesic and calming effects[5], and also has good anti-inflammatory[6-8]and broad-spectrum antibacterial effect[9]. Because of good medicinal function, it has been currently used for disease prevention in humans. However, whether Herba Picriae can be used for disease prevention or growth promotion of livestock and poultry has not been reported yet. In this study, the extract of Herba Picriae was used as a feed additive to feed Guangxi partridge chickens, and its effects on the growth performance and immune organs of the chickens were observed, so as to provide reference for the future use of Herba Picriae in feed additives for livestock and poultry.

2 Materials and methods

2.1 MaterialsExtract of Herba Picriae was prepared by the Pharmacology Laboratory of College of Animal Science and Technology in Guangxi University. The content of picfeltarraenins in the extract was higher than 7.5%.

2.2 Experimental animal and diet compositionTotal 500 one-day-old Guangxi partridge chickens were purchased from Guangxi Nanning Fufeng Agriculture and Animal Husbandry Co., Ltd. The diets for the early (1-21 days old), middle (22-49 days old) and late (50-105 days old) stages of the experiment were mainly composed of corn and soybean meal (Table 1) and were prepared according to the nutritional requirements of broilers stipulated by Feeding Standard of Chicken (NY/T 33-2004).

Table 1 Composition and nutrition level of basal diet

Ingredient∥%Age∥d1-2122-4950-105Nutritional levelAge∥d1-2122-4950-105Corn55.0860.0964.99Metabolic energy∥MJ/kg12.3112.1311.70Soybean meal 33.029.0025.0Crude protein∥%21.7919.9618.33Wheat bran 2.003.005.0Lysine∥%1.2881.1601.075Soybean oil 3.02.0Methionine∥%0.5430.4930.476Fish meal3.02.01.0Methionine +cystine/%0.8880.8210.793Limestone 1.01.11.2Calcium∥%0.9860.8870.898Salt 0.30.30.3Total phosphorus∥%0.6730.6380.632Dicalcium phosphate 1.31.21.2Available phosphorus∥%0.4320.4010.390L-lysine0.120.130.13DL-methionine0.20.180.18Premix1.01.01.0

Note: ① For each kilogram of diet, the premix provides: VA, 12 500 IU; VD3, 2 500 IU; VE, 20 IU; VK3, 20.5 mg; VB1, 2 mg; VB2, 6 mg; VB12, 0.025 mg; biotin, 0.032 mg; folate, 1.25 mg; pantothenic acid, 12 mg; niacin, 50 mg; Cu, 8 mg; Zn, 75 mg; Fe, 80 mg; Mn, 100 mg; Se, 0.15 mg; I, 0.35 mg. ② The nutrient levels in the table are calculated values.

2.3 Experimental design and feeding and managementThe experiment was conducted on the experimental chicken farm of Animal Husbandry Research Institute of Guangxi Zhuang Autonomous Region on October 9, 2015. From day 1 to day 21, the experimental chickens were housed in brooder equipped with automatic temperature control system. From day 1 on, the chickens were fed the basal diet and drinking wateradlibitum, and other feeding and management measures such as heat preservation, ventilation and lighting were the same as conventional. Single-factor completely randomized experiment was designed. A total of 500 one-day-old Guangxi partridge chickens were randomly divided into five groups, five replicates for each group and 20 chickens for each replicate. Groups A, B and C were treatment groups, in which 0.70%, 0.35% and 0.175% of Herba Picriae extract was added to the basal diet, respectively. Group D was a positive drug control group, in which 0.01% colistin sulfate premix (containing 10% colistin sulfate, produced by Xi’an Ledao Biotechnology Co., Ltd., batch No. 20150901) was supplemented to the basal diet. Group E was a blank control group, and the chickens in the group were fed only the basal diet. The experimental period was 105 d, of which the administration period was 70 d, followed by the follow-up observation period. During the experiment, immunization was conducted according to the production routine (Table 2). Except for the diet composition, the feeding conditions were the same in all groups during the whole experimental period.

Table 2 Immunization program for experimental chickens

Age∥dName of vaccineVaccination methodDosageManufacturer and batch No.1Anti-Mareks disease vaccineSubcutaneous injection0.2 mLWinsun, Guangdong (2015002)3ND-IB freeze-dried vaccineNasal dripFor 1 chickenWinsun, Guangdong (2015002)10ND-IB freeze-dried vaccineIntraocular-nasal dripFor 1 chickenWinsun, Guangdong (2015002)ND-IB oil emulsion vaccineSubcutaneous injection0.3 mLWinsun, Guangdong (2015004)Avian influenza (H5-H9) oil emulsion vaccineSubcutaneous injection0.3 mLSinder, Shandong (20150302)15IBD attenuated vaccine + milk powderDrinking waterFor 2 chickensWinsun, Guangdong (2015002)35ILT attenuated vaccineDrip to right eyeFor 0.5 chickenWinsun, Guangdong (2015001)

2.4 Determined indexes and methods

2.4.1Body weight and feed intake. The empty body weight of the chickens in each group was weighed in the morning of days 21, 35, 49, 70 and 105, respectively. The average daily body weight gain was calculated. In addition, the average daily feed intake was measured and the feed to gain ratio was calculated according to the following formula:

Feed to gain ratio=Average daily feed intake (g)/Average daily body weight gain (g).

2.4.2Immune organ index. At the age of 21, 35 and 49 d, five chickens were randomly selected from each group and weighed and sacrificed by jugular vein bleeding, respectively. The spleen, thymus and Fabricius bursa of each chicken were taken out. After removing fat and mesentery and absorbing blood with filter paper, the wet weight of the organs was measured with electronic balance. The immune organ index was calculated according to the following formula:

Immune organ index (%)=Wet weight of immune organ/body weight×100.

2.5 Data processingExperimental data were subjected to one-way ANOVA using SPSS 16.0 software, and multiple comparisons were performed with Duncan’s method. Results are expressed as mean ± standard deviation.

3 Results

3.1 Effects of Herba Picriae extract supplementation to diet on growth performance of experimental chickensThe average daily body weight gains of the experimental chickens at various stages are shown in Table 3. As shown in Table 3, the average daily body weight gains of the chickens in groups A and B differed insignificantly from those of the chickens in group E or D in all the five stages (P>0.05), indicating that dietary supplementation of 0.70% and 0.35% Herba Picriae extract had no obvious effect on the production performance of Guangxi partridge chickens. In the age ranges of 22-35 and 71-105 d, the average daily body weight gains of group C were significantly higher than those of group D (P<0.05). The average daily body weight gain of group C differed insignificantly from that of group D in the age range of 22-35 d (P>0.05), but in the age range of 71-105 d, the average daily body weight gain of group C was higher than that of group D (P<0.05). In the age ranges of 1-21, 22-49 and 50-70 d, group C showed a significant improvement trend compared to group E (P>0.05). The results about feed to gain ratio (Table 5) show that in the age range of 22-35 d, the feed to gain ratio of group A was significantly lower than those of groups B and C (P<0.01), but there was no significant difference between groups A, B and C and group E or D (P>0.05); and in the remaining age ranges, there was no significant difference among the five groups either (P>0.05).

Table 3 Effect of Herba Picriae extract on average daily body weight gain of experimental chickens g

Note: Different lowercase letters in the same row indicate significant differences at the 0.05 level. The same as below.

3.2 Effects of Herba Picriae extract supplementation to diet on average daily feed intake and feed to gain ratio of experimental chickensThe effects of dietary supplementation of Herba Picriae extract on average daily feed intake and feed to gain ratio of the experimental chickens are shown in Table 4 and Table 5. Table 4 shows that in the age range of 1-21 d, the average daily feed intakes in groups A and C were significantly higher than that in group E (P<0.05), but no significant difference was found between group B and group E (P>0.05); and there was no significant difference between groups A, B and C and group D (P>0.05). In the subsequent stages from day 22 to day 105, although no significant difference was observed in average daily feed intake between the five groups (P>0.05), the average daily feed intakes of groups A and C at each stage tended to increase in comparison to that of group E.

Table 4 Effect of Herba Picriae extract on average daily feed intake of experimental chickens g

Table 5 Effect of Herba Picriae extract on feed to gain ratio of experimental chickens g

3.3 Effects of Herba Picriae extract supplementation to diet on immune organ index of experimental chickensTable 6 shows that at the ages of 21, 35 and 49 d, there was no significant difference in thymus index or spleen index among the five groups (P>0.05). At the age of 21 d, the bursal indexes of groups A and C were significantly higher than that of group E (P<0.01), but there was no significant difference between group B and group E (P>0.05); and the bursal index of group A was also significantly higher than that of group D (P<0.05), but no significant difference was found between groups B and C and group D (P>0.05). At the age of 35 d, there was no significant difference among the five groups (P>0.05). On day 49, the bursal index of group B was significantly lower than that of group E (P<0.05), the differences between groups A and C and group E, and between groups A, B and C and group D were insignificant (P>0.05).

Table 6 Effect of Herba Picriae extract on immune organ index of experimental chickens %

4 Discussion

4.1 Effects of Herba Picriae extract on growth performance and feed intake of experimental chickens and utilization of feedBecause of good medicinal function, Herba Picriae has been made into a variety of Chinese patent medicines widely used in human disease prevention[10-12]. However, whether it can be used for disease prevention or growth promotion of livestock and poultry has not been reported so far. In this experiment, three different dosages of Herba Picriae extract were added to the basal diet for Guangxi partridge chickens, and at the addition dosage of 0.175%, the average daily body weight gains in the age ranges of 22-35 and 71-105 d significantly increased, and those in the age ranges of 1-21, 36-49 and 50-70 d tended to increase. This shows that dietary supplementation of 0.175% of Herba Picriae extract can improve the growth performance of Guangxi partridge chickens. Although the duration was only 70 d, the average daily body weight gain of group C in the age range of 71-105 d was already significantly higher than that of group E, indicating that Herba Picriae extract still has a significant effect or promotion on the growth of the chickens after drug administration. The mechanism for Herba Picriae extract’s improving growth performance of the experimental chickens has not been clarified yet. This may be related to the heat-clearing, detoxifying, central sedative, calming and analgesic functions and good anti-inflammatory and broad-spectrum antibacterial effects of Herba Picriae. Although the use of Herba Picriae in promoting growth of livestock and poultry, especially chickens has not been reported in previous studies, it has been proved that some other Chinese herbal medicine additives with similar functions or effects do have the effect of increasing feed intake and promoting chicken growth performance[13-15], and so, more research should be conducted on the growth promotion effect of Herba Picriae extract on chickens.

Although Herba Picriae has bitter taste, it did not produce a negative impact on the feed intake of the chickens. On the contrary, the dietary supplementation of 0.70% and 0.175% of Herba Picriae extract significantly increased the feed intake of the experimental chickens in the age range of 1-21 d, and tended to increase their feed intake in the follow-up stages, by 2.4%-9.2%. This shows that adding 0.175% of Herba Picriae extract to the diet can increase the feed intake of chickens to a certain extent. The increase in the feed intake might be the main reason for the improvement of growth performance of the chickens in group C. Therefore, the feed to gain ratio did not show significant difference between group C and group E from beginning to end. Although the average daily feed intake of the chickens in group A significantly increased, their daily body weight gain did not increase. The reason might be that the improvement of chicken growth performance would be achieved by multiple factors, in addition to feed nutrition. The results of this experiment show that dietary supplementation of 0.175% of Herba Picriae extract had already achieved better results. The addition dosage of Herba Picriae extract in group A (0.70%) was four times that of group C. Whether the excessive addition of Herba Picriae extract affects the growth of the experimental chickens from other aspects still needs further research.

4.2 Effect of dietary supplementation of Herba Picriae extract on immune organ index of experimental chickensThe results of this experiment show that the addition of Herba Picriae extract had no effect on the thymus index and spleen index of the chickens in groups A, B and C. However, the bursal indexes of groups A and C were significantly higher than that of group E at the age of 21 d, indicating that dietary supplementation of 0.70% and 0.175% of Herba Picriae extract could significantly promote the growth and development of Fabricius bursae in chickens. Fabricius bursa is a unique immune organ of poultry. Its inner lymphoid epithelial structure is an important place for the formation, induction and differentiation of B cells, and the B cells produced here are involved in the body’s humoral immunity[16-17]. Fabricius bursa is an important part of body’s immunity. Therefore, the growth of Fabricius bursa means the improvement of the body’s immunity. This study shows that the dietary supplementation of 0.70% and 0.175% of Herba Picriae extract can improve the immune performance of the experimental chickens to a certain extent. However, there was no significant difference in bursal index between group B with Herba Picriae extract addition dosage of 0.35% and group E, and at the age of 49 d, the bursal index of group B was even significantly lower than that of group E. This might be because that Fabricius bursa is a more characteristic immune organ, and because of short growth and development time, its degradation is rapid. For example, the growth of Fabricius bursae in Beijing fatty chickens has reached a peak at the age of 1, 2 and 3 weeks and then declines rapidly during the age range of 4-6 weeks[18]. The results of this experiment have a similar trend. The bursal indexes of all the groups at the age of 35 and 49 d were significantly lower than those at the age of 21 d; and the bursal indexes of the other groups were not lower than that of group E at any stage, except for that of group B at the age of 49 d. The bursal indexes of groups A, B and C were not lower than that of the positive drug control group D at the age of 21 and 49 d, and although the bursal indexes of the three groups were lower than that of group D at the age of 35 d, the differences were insignificant (P>0.05). Therefore, the phenomena appearing in the bursal index of group B might be related to the rapid degeneration of Fabricius bursa at the late stage and the differences between the individual experimental chickens. Of course, the mechanism needs to be studied.

5 Conclusions

Among the three addition dosages of Herba Picriae extract studied in this experiment, the supplementation of 0.175% of Herba Picriae extract to the diet can increase the feed intake of Guangxi partridge chickens to a certain extent, and it can also significantly improve the growth performance and 21-day-old bursal index of the chickens, and so, the addition dosage of 0.175% is better.