Effects of Chinese Herbal Medicine Feed Additives on Growth Performance and Dietary Nutrient Metabolism of Black-bone Chickens

Cui YANG, Fulin WANG, Siqian WU, Zhuyue WU, Limei QIN, Huofu WAN, Zhengzhong XIAO, Chunhua HUANG, Jiahuang YANG, Fengying WEI*

1. Guangxi Vocational University of Agriculture, Nanning 530009, China; 2. Animal Husbandry Research Institute of Guangxi Zhuang Autonomous Region, Nanning 530001, China; 3. Guangxi Silk Road Agriculture Co., Ltd., Qinzhou 535008, China

Abstract [Objectives] To study the effects of Chinese herbal medicine feed additives on the growth performance and dietary nutrient metabolic rate of black-one chickens. [Methods] 480 pieces of 1-day-old Donglan Black-bone Chickens were selected and divided into 4 groups, with 6 replicates in each group, with 20 pieces in each replicate. Among them, group A was the control group and was fed the basal diet; the groups B, C, and D were the experimental groups, which were separately supplemented with 0.25%, 0.50% and 1.00% of Chinese herbal medicine additives in the basal diet, and the experimental period was 70 d. At the end of the feeding experiment, 24 experimental chickens with similar body weight were selected from each group, and the same design of the feeding experiment was used to continue to feed the original diet for the metabolic experiment to determine the nutrient metabolic rate. [Results] Except the 50-70 d stage, the average daily gain (ADG) of group B in other stages was increased by 5.00%-9.15% (P<0.05), and the average body weight of group B at 70 d was also increased by 4.86% (P<0.05); the ADG of group C at 36-49, 1-49 and 1-70 d and the average individual weight at 70 d were also higher than that of group A by 5.90%, 2.66%, 2.68% and 2.57%, respectively (P>0.05); at 36-49 d, the average daily feed intake (ADFI) of group A was higher than that of group B by 6.04% (P<0.01), and was also higher than that of groups C and D by 5.12% and 4.13% (P<0.05), respectively; at 1-49 d, the ADFI of group A was higher than that of group C by 2.86% (P<0.05), and there was no significant difference between the four groups of experimental chickens at each stage (P>0.05); at 22-35 and 1-70 d, the feed to gain ratio (F/G) of group B was 6.32% and 3.41% lower than that of group A (P<0.05), and at 36-49 and 1-49 d, the F/G of group B was even lower; at 36-49 d, the F/G of group C was 10.15% lower than that of group A (P<0.05), and at 1-49 d, it was also lower than that of group A by 5.29% (P<0.01); there was no significant difference between the two groups at other stages. In terms of nutrient metabolism: the three different amounts of this additive have increased the metabolic rate of DM, CP, CF, NFE, CA, Ca, P, TE and other nutrients in the diet to varying degrees, especially the addition of 0.25% and 0.50% had the significant increase. [Conclusions] The addition of 0.25% Chinese herbal medicine additives in the diet can significantly improve the growth performance and main nutrient metabolic rate of Donglan Black-bone Chickens.

Key words Donglan Black-bone Chickens, Chinese herbal medicine additives, Growth performance, Nutrient metabolic rate, Antioxidant effect

1 Introduction

With good disease resistance and growth-promoting properties, feed antibiotics have played a very important role in the development of China’s livestock and poultry breeding industries. In China’s livestock and poultry production, a large volume of feed antibiotics have been used for a long time. However, excessive use of feed antibiotics has brought about a lot of side effects, accordingly posing a lot of risks to the breeding industry. In this situation, China had to adopt a "ban on the use of antibiotics in feed"[1-4]. However, no corresponding substitutes for antibiotics have yet been found. Finding suitable substitutes has become a priority. Extensive studies have shown that traditional Chinese herbal medicines contain a variety of biologically active substances, which have good antibacterial, disease resistance and growth promoting effects, and compound Chinese herbal medicine additives have better effect because they contain many kinds of bioactive substances[5-7]. Although these studies have initially shown the feasibility of Chinese herbal medicine as an alternative to antibiotics, there are still many problems to be solved, such as the quality of additives, the efficiency of biologically active substances, the stability of the effect and its mechanism,etc.[5]. Thus, it is still necessary to make further and in-depth study. In this study, according to factors such as the type and content of main biological active substances contained in each component in traditional Chinese medicine and its formula, we used ten Chinese herbal medicines such as Forsythiae Fructus, Angelicae Sinensis Radix, Astragali Radix and Crataegi Fructus as additives to conduct breeding and metabolic experiments on Donglan Black-bone Chickens of Guangxi. We studied the effects of Chinese herbal medicine additives on the growth performance and feed nutrient utilization efficiency of black-bone chickens, explored the possibility of using them as antibiotic substitutes, to provide a scientific basis for finding substitutes of antibiotics.

2 Materials and methods

2.1 Chinese herbal medicine additivesThe Chinese herbal medicine additives (hereinafter referred to as additives) used in this experiment were provided by Guangxi Yixin Pharmaceutical Co., Ltd., consisted of ten Chinese herbal medicines such as Forsythiae Fructus, Astragali Radix, Angelicae Sinensis Radix,etc., pulverized through a 100-mesh sieve and then bagged for experiment.

2.2 Experimental diets and nutritional levelsThe experimental feed was provided by Nanning Liyuan Grain, Oil and Feed Co., Ltd., the specific formula is secret; the raw materials include maize, wheat, sorghum and other grains and soybean meal, fish meal, calcium hydrogen phosphate, L-lysine sulfate, copper sulfate, ferrous sulfate, zinc sulfate, calcium propionate, methionine hydroxy analog (MHA), vitamin A, vitamin D3, vitamin E, vitamin K3,etc.The main nutrient levels of the diets at different stages are listed in Table 1.

Table 1 Nutrient level of different basal diets %

2.3 Experimental animals, design and feeding management

2.3.1Feeding experiment. The one day old Donglan Black-bone Chickens used in the experiment were provided by Guangxi Liteng Agriculture and Animal Husbandry Development Co., Ltd., with a total of 480 pieces (all female chickens). A single factor completely randomized design was adopted, and the experimental chickens were divided into 4 groups, 6 replicates in each group and 20 pieces in each replicate. Among them, group A was the control group and was fed the basal diet; the groups B, C, and D were the experimental groups, which were separately supplemented with 0.25%, 0.50% and 1.00% of Chinese herbal medicine additives in the basal diet. The experiment was carried out on November 9, 2020 at the Poultry Research Laboratory Experimental Base of Animal Husbandry Research Institute of Guangxi, with an experimental period of 70 d. Before 21 d, the chickens were raised in the brooding room, and the temperature was controlled manually. The initial room temperature was controlled at 33 ℃, and after one week, the temperature was lowered by 1 ℃ every 2 d, and maintained at 30 ℃ before 21 d. During the experiment, the experimental chickens had free access to food and water, and the feeding management and immunization procedures were carried out in accordance with the production routines.

2.3.2Metabolic experiment. At the end of the 70-d feeding experiment, 24 experimental chickens with similar body weight were selected from each experimental group, a total of 96 chickens, with the same design as the original feeding experiment, divided into 4 groups, each group was set up with 6 replicate, 4 chickens in each replicate; continued to feed the diets used in the previous experimental groups; carried out a 6-d metabolic experiment; the first 3 d were the preliminary experiment period, and the collection of feces was carried out on the next 3 d. During the sampling period, all chicken feces from the experimental chickens on the previous day were collected at 8:00 every morning, then removed feathers, dander and other sundries, collected samples after uniformity, sprayed with 10% sulfuric acid, bagged and sealed after uniformity, and stored at -20 ℃. Then the Animal Nutrition Laboratory of Animal Husbandry Research Institute of Guangxi determined various nutrients and AIA content. Metabolic experiment method: 4N hydrochloric acid insoluble ash (4NHCl·AIA) method.

2.4 Measurement indicators and methods

2.4.1Determination of body weight, feed intake and feed to gain ratio (F/G). The fasting body weight of the experimental chickens in each group was weighed at the beginning of the experiment, 21, 35, 49 and 70 d in the morning (8:00) before feeding; calculated the corresponding average daily gain (ADG); measured the feed intake of the experimental chickens during these periods and calculated the corresponding average daily feed intake (ADFI); finally, calculated the feed to gain ratio (F/G) of the experimental chickens according to theADGandADFIof each stage using the Formula (1):

F/G=ADFI(g)/ADG(g)

(1)

2.4.2Determination of dietary nutrient metabolic rate. The samples collected during the metabolic experiment were thawed, dried at 60 ℃, pulverized and bagged before the formal start of the measurement; finally, measured the nutrient and AIA contents in samples. In addition, calculated the metabolic rate of various nutrients in the diet using the formula used in the 4NHCl·AIA method, namely, the Formula (2):

DC(%)(nutrient metabolic rate)=100-100[(A1/A2)×(F2/F1)]

(2)

whereA1denotes AIA content (%) in the feed,A2refers to AIA content in feces (%),F1means nutrient content in the feed (%), andF2stands for nutrient content in feces (%).

2.5 Processing of experimental dataThe experimental data were preliminarily processed with the aid of Excel software, and one-way ANOVA was performed using SPSS 16.0 statistical software. The means between groups were compared by Duncan’s method, and the results were expressed as the mean±standard deviation.

3 Results and analysis

3.1 Effects of Chinese herbal medicine additives on the growth performance of experimental chickens

3.1.1ADG results of experimental chickens. As shown in Table 2, during the whole experimental period, except 50-70 d stage, the ADG of group B in other stages increased by 5.00%-9.15% (P<0.05), and the average body weight of 70 d also increased by 4.86% (P<0.05). At 36-49, 1-49, 1-70 d stages and 70 d, the ADG and average body weight of group C was also increased by 5.90%, 2.66%, 2.68% and 2.57%, respectively compared with group A, but none of them reached the level of statistical difference (P>0.05), and there was no significant difference in other stages between the two groups (P>0.05); the ADG and average body weight of group D at 36-49, 1-70 and 70 d also increased compared with group A (P>0.05), but there was no significant difference in other stages between the two groups (P>0.05). These indicate that the addition of 0.25% Chinese herbal medicine additives in the diet can significantly improve the weight gain performance of the experimental chickens; among the three experimental groups, group B had the greatest weight gain.

Table 2 ADG of experimental chickens at different stages (g)

3.1.2Effects on the average daily feed intake (ADFI). As shown in Table 3, at 36-49 d, theADFIof group A was 6.04% higher than that of group B (P<0.01), and it was 5.12% and 4.13%, respectively higher than that of groups C and D (P<0.05), and at 1-49 d, the ADFI of group A was 2.86% higher than that of group C (P<0.05). However, in other stages, especially at 1-70 d, there was no significant difference in ADFI of the four groups of experimental chickens (P>0.05). These show that none of the three additions of Chinese herbal medicine additives can increase the average daily feed intake of the experimental chickens, and there is no adverse effect either.

Table 3 The ADFI of experimental chickens at different stages

3.1.3Effects on the feed to gain ratio (F/G). According to the data in Table 4, at 1-21 and 50-70 d, there was no significant difference inF/Gbetween groups A and B (P>0.05). But at 22-35 and 1-70 d, theF/Gof group B was separately lower than that of group A by 6.32% and 3.41% (P<0.05), and at 36-49 and 1-49 d, theF/Gof group B was lower than that of group A by 11.43% and 7.31%, respectively (P<0.01). At 36-49 d, theF/Gof group C was lower than that of group A by 10.15% (P<0.05), and at 1-49 d, theF/Gof group C was also lower than that of group A by 5.29% (P<0.01). However, in other stages, there was no significant difference between the two groups (P>0.05). At 36-49 d, theF/Gof group D was lower than that of group A by 7.27% (P<0.05); at 1-21 d, theF/Gof group A was lower than that of group D by 5.43% (P<0.05). In addition, there was no significant difference between the two groups (P>0.05). Therefore, among the three experimental groups, the experimental chickens of group B with the addition of 0.25% significantly reduced the feed to gain ratio. In other words, the addition of 0.25% could significantly improve the feed conversion efficiency (feed to gain ratio).

Table 4 The F/G of experimental chickens at different stages

3.2 Effects on dietary nutrient metabolic rateFrom the data in Table 5, it can be known that compared with group A, the metabolic rate of DM in groups B and C increased by 5.75% and 6.41%, respectively (P<0.01), and group D was also higher than that in group A by 5.20% (P<0.05). Compared with group A, the metabolic rate of CP in groups B, C, and D increased by 4.26%, 4.20%, and 3.97%, respectively, (P<0.05). However, there was no significant difference in the metabolic rate of EE among the four groups (P>0.05). The metabolic rate of CF in groups B and C was significantly higher than those in group A (P<0.01), and the metabolic rate of CF in group D was also significantly higher than that in group A (P<0.05). Compared with group A, the TE metabolic rate of groups B, C, and D was increased by 2.85%, 2.78%, and 2.81%, respectively (P<0.05). The metabolic rate of NFE in group B was significantly higher than that in group A (P<0.01), and the metabolic rate of NFE in groups C and D was also significantly higher than that in group A (P<0.05). The metabolic rate of CA in group C was significantly higher than that in group A (P<0.01), and the metabolic rate of CA in groups B and D was also significantly higher than that in group A (P<0.05). Compared with group A, the metabolic rate of Ca in groups B and C were 20.24% and 22.84% higher, respectively (P<0.01), and the metabolic rate of Ca in group D was 13.59% higher than that in group A (P<0.05). The metabolic rate of P in groups B and C was separately 24.86% and 24.03% higher than that in group A (P<0.01), and the metabolic rate of P in group D was 19.04% higher than that in group A (P<0.05). These indicate that the three different volumes of Chinese herbal medicine additives have different degrees of improvement in the metabolic rate of the main nutrients in the diet, and the addition of 0.25% and 0.50% has more significant improvement.

Table 5 Dietary nutrient metabolic rate of experimental chickens %

4 Discussion

Donglan Black-bone Chickens are mainly distributed in 14 townships such as Donglan and Aidong in Donglan County, and surrounding counties and townships of Guangxi Zhuang Autonomous Region, with an annual output of more than 1 million chickens. They are excellent local chickens in Guangxi. Donglan Black-bone Chickens are black all over the body, with light black skin, meat, bones and internal organs[8]. This variety of chicken is small and medium in size, with an adult (150 d) rooster 1.3-2.5 kg and a hen 1.1-2.0 kg; at 120 d, the average weight of roosters is 1 336.6 g, the daily gain is 11.1 g, and the hens are 913.9 g, and the daily gain is 8.4 g[9]. Donglan black-bone chickens are widely favored for their advantages of rough feeding resistance, strong disease resistance, tender meat, delicious meat and high medicinal value[10].

In this study, 0.25%, 0.50% and 1.00% of Chinese herbal medicine additives were separately added to the diets of three experimental groups B, C and D of Donglan Black-bone Chickens. When feeding to 70 d, the ADG of group B was significantly increased than that of control group A, among which the increase was 6.76% and 5.00% at 1-49 or 1-70 d, respectively, and the difference was significant. Although group C showed a certain improvement trend compared with group A, it did not reach the level of statistical difference. These indicate that the addition of 0.25% Chinese herbal medicine additives in the diet has a good effect on the growth of the experimental chickens, and also indicate that this addition level of the diet is suitable. Proper Chinese herbal medicine additives can promote the growth of chickens, and the reason may be related to the biologically active components contained in various Chinese herbal medicines in the additives. Astragali Radix, Angelicae Sinensis Radix, Citri Reticulatae Pericarpium, Crataegi Fructus, Glycyrrhizae Radix Et Rhizoma,etc.used in this experiment separately contain such active components as polysaccharides, flavonoids, volatile oils, and alkaloids to varying degrees[10-15].

Studies have shown that polysaccharides can promote the proliferation of beneficial bacteria in the digestive tract while inhibiting the reproduction of harmful bacteria, so it can improve the intestinal micro-ecosystem and maintain intestinal health; polysaccharides can also promote the growth of micro-intestinal hairs in the duodenum and jejunum, and increase the surface area of the intestinal tract for nutrient absorption; in addition, polysaccharides can up-regulate the expression of carbohydrate-active enzyme (CAZymes) genes and improve the activities of CAZymes[16-17]. Therefore, polysaccharides can improve the digestion and absorption of feed nutrients, thereby promoting animal growth. After adding compound Chinese herbal polysaccharides to chicken diets, researchers[18-19]found that they could significantly improve chicken growth performance.

Flavonoids have antioxidant, immune regulation and growth-promoting functions. Wang Shijinetal.[20]added 750 mg/kg flavonoids ofArtemisiaargyito the AA rooster diet, and found that it significantly increased the ADG for 22-42 d and significantly decreased theF/G. After adding hesperidin (also called bioflavonoids) to the diet of AA male chicks, Jiang Yangetal.[21]found that it also significantly increased the ADG at 22-42 or 1-42 d, and significantly reduced theF/G. Studies have shown that flavonoids can increase the villus height and crypt depth of the small intestine, and promote intestinal development by increasing the activity of intracellular alkaline phosphatase and the synthesis of DNA in intestinal epithelial cells. In addition, flavonoids can also promote gastrointestinal motility, accelerate the digestion of chyme, and improve the utilization efficiency of feed.

Volatile oils, also known as essential oils, plant essential oils (PEO) can increase the palatability of feeds and stimulate the secretion of digestive juices and mucus in the gastrointestinal tract. Volatile oils can inhibit the reproduction of harmful bacteria in the digestive tract, adjust and stabilize the microflora of the digestive tract. PEO can also increase the villus height and crypt depth of the intestinal tract, increase the surface area of the small intestinal villi, and improve the digestion and absorption of the intestinal tract[22-23]. The results of experiments supplemented with PEO in broiler diets also showed that PEO significantly increased trypsin, α-amylase and intestinal maltase activities[24], thus it could improve the digestibility of feed nutrients, improve the absorption and utilization of nutrients. Therefore, adding an appropriate amount of PEO to the diet can significantly improve the growth performance and feed utilization efficiency of chickens[25-26], and the effect of adding compound PEO is better than that of single PEO[27]. Furthermore, the above bioactive components also have antibacterial, antiviral and antioxidant effects[28-30], thus they can eliminate the influence of certain negative factors on the growth of chickens and further promote the growth and development of chickens. According to some studies[7,31-34], Chinese herbal medicine additives composed of Astragali Radix, Angelicae Sinensis Radix, Citri Reticulatae Pericarpium, Crataegi Fructus, Glycyrrhizae Radix Et Rhizoma,etc.as the main components have a good effect on the growth performance of chickens. The results of this study are also very similar, and once again prove the growth-promoting effect of such additives on chickens.

During this experiment, the ADG of group B was significantly higher than that of group A, but there was no significant difference inADFIbetween the two groups, so theF/Gof group B was lower than that of group A, showing that the addition of 0.25% Chinese herbal medicine additives in the diet can significantly reduce theF/Gof chickens, namely, improve the feed conversion efficiency. In other words, the improvement of the growth performance of the experimental chickens in group B was achieved through the improvement of feed conversion efficiency. This is of great significance for production practice, as production efficiency can be improved without increasing feed costs.

In summary, from the results of the metabolic experiment, we can see that the three different additive amounts of the additive can improve the metabolic rate of the main nutrients in the diet to varying degrees, and the 0.25% and 0.50% additive amount has the best improvement effect. This again demonstrates that the improvement of the growth performance of the B group experimental chickens with 0.25% of the diet is achieved through the improvement of the feed conversion efficiency. However, why did the improved feed conversion efficiency of the other two groups, especially group C, not bring about improved growth performance? The reason may be related to the addition amount of additives, because the addition amount of group C is twice as high as that of group B, and the amount of group D is three times higher than that of group B. What is its mechanism? Is there any other reason besides this? It is not yet known? Therefore, further study is needed.