Development of technological methods of growing and use the plant extracts to improve the meat quality of broiler chicken

Abstract

Poultry products are an indispensable food source in people's daily life and ensuring their greenness, environmental protection and safety is an important part of food safety. However, in recent years, with the increasing intensification of the poultry farming industry, to improve economic benefits, farmers use antibiotics heavily in feed, which has brought great harm to human health and environmental safety. Under the background of comprehensive "antibiotic prohibition", exploring "new, efficient, safe and green" antibiotic substitutes has gradually become a research hotspot in the feed industry. In recent years, many studies have found that plant extracts have strong immune regulation activity, can enhance the immune function of the body, have the advantages of green, environmental protection, safety, and non-toxicity, and can act on immune cells in the body, thereby regulating the immune state of the body. It plays an important role in resisting the invasion of various pathogenic bacteria. Astragalus is one of the traditional Chinese medicines. Astragalus contains polysaccharides, proteins, alkaloids, amino acids, flavonoids, and other active substances, which have the functions of regulating animal immune function, anti-oxidation, anti-tumor, and anti-infection. As one of the traditional Chinese herbal medicines, Glycyrrhiza contains rich bioactive substances such as triterpenoid saponins, flavonoids, coumarin, alkaloids, volatile oils, organic acids, and sugars. It has been concerned about its biological activity functions such as antioxidant, antibacterial, antiviral, anticancer, anti-inflammatory, immune regulation, hypoglycemic, and other biological activities. In addition, Glycyrrhiza also has antitussive, expectorant, antiasthmatic, lung protection, and anti-respiratory pathogenic effects. However, the current research on Astragalus extract and Glycyrrhiza extract mostly focuses on the effects on animal production performance. There are relatively few studies on intestinal health and respiratory health and their compatibility applications. Therefore, it is of great significance to research the feeding effect and mechanism of Astragalus extract and Glycyrrhiza extract on broilers and use the Astragalus extract and Glycyrrhiza extract in poultry production as new antibiotic substitutes. The first part of this paper reviewed the physiological functions of Astragalus, such as anti-inflammatory, immune regulation, regulation of mucosal immune barrier, antioxidant, anti-cancer, and its application in improving poultry production performance, intestinal function, and disease resistance (P31-38). The antiviral function, anti-inflammatory function, antioxidant function, immune regulation function, and improved gut health of Glycyrrhiza were also reviewed (P39-43). The physical barrier, chemical barrier, microbial barrier, immune barrier, and the evaluation of the function of the poultry intestinal barrier were reviewed (P44-49). The structure and function of the mechanical barrier, chemical barrier, microbial barrier, and immune barrier of the respiratory mucosa of poultry were reviewed (P50-52). In addition, the effect of high temperature boiled technology on the nutrient content of chicken was reviewed (P60-61). The purpose of the experiment is to study the feeding effects of Astragalus extract and Glycyrrhiza extract on broilers and their effects on intestinal health and respiratory health and to explore their potential mechanism of action. This research will supply a new type of antibiotic substitute in broiler feed, and provide a theoretical basis for the application of Astragalus extract and Glycyrrhiza extract in poultry production. The research content of the experiment includes the following parts: (1) Effects of Astragalus extract and Glycyrrhiza extract on production performance, nutrient metabolic rate, and meat quality of broilers; (2) Effects of Astragalus extract and Glycyrrhiza extract on immune function, antioxidant function and inflammatory factors in broilers; (3) Potential mechanisms of the effects of Astragalus extract and Glycyrrhiza extract on the intestinal barrier and respiratory tract barrier of broilers. (4) The effects of adding Astragalus extract and Glycyrrhiza extracts to broiler diets on meat quality traits of chicken meat treated by high temperature water boiling technology, such as color, shear strength, nutrient composition and fatty acid content. In the second part (P64-74), the experimental design is carried out according to the research topic of this paper. 720 1-day-old Arbor Acres broiler chickens were selected and randomly divided into 6 treatments with 6 replicates comprising 20 broilers each. All the animals were managed according to the guidelines for the care and use of experimental animals approved by The Ethics Committee of Henan Agricultural University (No. HNND2021031503). The control group (CON) was fed the basal diet without antibiotics, and the antibiotic group (ANT) was fed the basal diet supplemented with 500 mg/kg of Terramycin calcium, the Astragalus extract group (AE) was fed the basal diet supplemented with 300 mg/kg of Astragalus extract, the Glycyrrhiza extract group (GE) was fed the basal diet supplemented with Glycyrrhiza extract 150 mg/kg, Astragalus extract + Glycyrrhiza extract Ⅰ group (AE + GE Ⅰ) was fed the basal diet supplemented with Astragalus extract 300 mg/kg and Glycyrrhiza extract 150 mg/kg, Astragalus extract +Glycyrrhiza extract II group (AE+GE II) was fed the basal diet supplemented with Astragalus extract 150 mg/kg and Glycyrrhiza extract 75 mg/kg. The experimental diets were fed for 42 d. The three part (P76-117): by measuring the production performance such as body weight, average daily gain, average daily feed intake, and feed conversion rate of broilers, the results showed that the groups added with plant extracts improved the average daily weight gain and energy metabolic rate of broilers and decreased the feed-to-weight ratio, which was no different from the effect of adding antibiotic on the performance of broilers. The fatty acid content of the muscle was measured by gas chromatography, and the pH value, shear force, and muscle color of the muscle were also measured. The results showed that the groups added with the plant extract increased the content of polyunsaturated fatty acids in the muscle, and the effect was better than that of antibiotics. Enzyme-linked immunosorbent assay was used to determine the immune indexes, antioxidant indexes, and inflammatory factors in serum. The results showed that AE+GE Ⅰ group and AE+GE II group increased thymus index and serum IgA content, the GE group and the AE+GE group increased serum IgM content, AE group, GE group, and AE+GE Ⅰ group increased serum IgG content, AE+GE II group increased spleen index. The groups added with plant extracts increased the SOD content of the trachea. In addition, the AE group increased the serum T-AOC content, the GE group increased the serum SOD content, the AE group and the GE group increased the tracheal T-AOC content, The content of MDA in serum was decreased, and the content of GSH-Px in the trachea was increased in GE group and AE+GE II group. Adding Astragalus extract and Glycyrrhiza extract was more effective than Terramycin calcium in improving the immune function and antioxidant function of broilers. The levels of TNF-α and IL-6 in serum were decreased in each group supplemented with plant extracts, the levels of IL-1β in serum were decreased in the AE group, GE group, and AE+GE II group, and IL-1β and IL-6 content in lungs were decreased in GE group and AE+GE II group. Adding plant extracts was as effective in suppressing inflammation as adding antibiotics. The intestinal slices were made by hematoxylin-eosin staining, and the mucosal morphology of the intestinal tract was observed by electron microscope. The villus height and the ratio of villus height to crypt depth for adding plant extracts groups were higher than that of ANT. The expression of tight junction protein and mucin in intestinal mucosa was determined by microspectrophotometer, and the content of DAO in serum was determined by enzyme-linked immunosorbent assay. NRF2 mRNA expression in duodenum, jejunum, ileum and trachea, SOD1, SOD2, GSH-Px mRNA expression in the duodenum, SOD1, GSH-Px mRNA expression in the jejunum, SOD1, SOD2, GSH-Px mRNA in ileum were increased in each group supplemented with Astragalus extract and Glycyrrhiza extract, and the DAO content was decreased. The results showed that adding Astragalus extract and Glycyrrhiza extract was more effective than antibiotics in improving the intestinal antioxidant function and permeability of broilers. Using high-throughput sequencing to analyze the microbial abundance of cecal contents, the results showed that the addition of Astragalus extract and Glycyrrhiza extract increased the diversity and richness of intestinal microorganisms, improved the structure of intestinal flora, increased the beneficial bacteria, and decreased the harmful bacteria. The effect is better than antibiotics in improving intestinal flora. Correlation analysis showed that Astragalus extract and Glycyrrhiza extract had effects on production performance, serum antioxidant function, immune function, inflammatory factors, intestinal mucosal morphology, and intestinal permeability by improving the structure of intestinal flora. The meat quality traits of broilers were determined by the method of high temperature boiled. The results showed that the high temperature boiled technology could improve the meat quality traits of broilers fed with Astragalus extract and Glycyrrhiza extract. The fourth and fifth Parts (P119-139): based on the above research, the following conclusions are drawn: the addition of Astragalus extract and Glycyrrhiza extract in the diet improves the production performance, the apparent metabolic rate of energy, the meat quality, antioxidant and immune function in broilers, and improves the intestinal mucosal morphology, intestinal and respiratory barrier function, inhibits the occurrence of pro-inflammatory factors. In addition, the high temperature boiled technology can improve the meat quality traits of broilers fed with Astragalus extract and Glycyrrhiza extract. It is speculated that Astragalus extract and Glycyrrhiza extract can affect production performance, serum antioxidant performance, immune function, inflammatory factors, intestinal mucosal morphology, and intestinal permeability by improving the structure of intestinal flora. Astragalus extract and Glycyrrhiza extract can be used in poultry production as an alternative to antibiotics. Among them, the feeding effect of adding 150 mg/kg Astragalus extract + 75 mg/kg Glycyrrhiza extract group was the best, and the feeding effect of adding Glycyrrhiza extract alone was better than that of adding Astragalus extract alone. In addition, adding Glycyrrhiza extract alone has the best economic benefits. This paper is the first to systematically study the effects of Astragalus extract, and Glycyrrhiza extract and their combined use on production performance, meat quality, antioxidant function, immune function, and intestinal barrier function of broilers. For the first time, through the analysis of gut microbial diversity, the possible mechanism was investigated for the effects of Astragalus extract and Glycyrrhiza extract on broilers by regulating gut microbes. The effect of high temperature boiled technology on meat quality traits of broilers fed with Astragalus extract and Glycyrrhiza extract was studied for the first time. The results of the study provide a theoretical basis for the replacement of antibiotics with Astragalus extract and Glycyrrhiza extract and their application in broiler production and provide an effective way for safe broiler food production. In the future, we will further study the mechanism of Astragalus extract and Glycyrrhiza extract and their combined use on the respiratory barrier function of broilers, and on the intestinal microbial metabolic pathway of broilers. This project was supported by the Central Plains High Level Talent Special Program (Grant No. 204200510010). Professor Kyselov Oleksandr from Sumy Agrarian University in Ukraine and Professor Wang Zhixiang from Henan Agricultural University designed the experiment. Professor Liu Changzhong from Henan University of Science and Technology provided funding support. Qiao Yingying independently completed the experiment and wrote a manuscript for this degree thesis. Professor Kyselov Oleksandr and Professor Wang Zhixiang proposed revisions. Poultry products are an indispensable food source in people's daily life and ensuring their greenness, environmental protection and safety is an important part of food safety. However, in recent years, with the increasing intensification of the poultry farming industry, to improve economic benefits, farmers use antibiotics heavily in feed, which has brought great harm to human health and environmental safety. Under the background of comprehensive "antibiotic prohibition", exploring "new, efficient, safe and green" antibiotic substitutes has gradually become a research hotspot in the feed industry. In recent years, many studies have found that plant extracts have strong immune regulation activity, can enhance the immune function of the body, have the advantages of green, environmental protection, safety, and non-toxicity, and can act on immune cells in the body, thereby regulating the immune state of the body. It plays an important role in resisting the invasion of various pathogenic bacteria. Astragalus is one of the traditional Chinese medicines. Astragalus contains polysaccharides, proteins, alkaloids, amino acids, flavonoids, and other active substances, which have the functions of regulating animal immune function, anti-oxidation, anti-tumor, and anti-infection. As one of the traditional Chinese herbal medicines, Glycyrrhiza contains rich bioactive substances such as triterpenoid saponins, flavonoids, coumarin, alkaloids, volatile oils, organic acids, and sugars. It has been concerned about its biological activity functions such as antioxidant, antibacterial, antiviral, anticancer, anti-inflammatory, immune regulation, hypoglycemic, and other biological activities. In addition, Glycyrrhiza also has antitussive, expectorant, antiasthmatic, lung protection, and anti-respiratory pathogenic effects. However, the current research on Astragalus extract and Glycyrrhiza extract mostly focuses on the effects on animal production performance. There are relatively few studies on intestinal health and respiratory health and their compatibility applications. Therefore, it is of great significance to research the feeding effect and mechanism of Astragalus extract and Glycyrrhiza extract on broilers and use the Astragalus extract and Glycyrrhiza extract in poultry production as new antibiotic substitutes. The first part of this paper reviewed the physiological functions of Astragalus, such as anti-inflammatory, immune regulation, regulation of mucosal immune barrier, antioxidant, anti-cancer, and its application in improving poultry production performance, intestinal function, and disease resistance (P31-38). The antiviral function, anti-inflammatory function, antioxidant function, immune regulation function, and improved gut health of Glycyrrhiza were also reviewed (P39-43). The physical barrier, chemical barrier, microbial barrier, immune barrier, and the evaluation of the function of the poultry intestinal barrier were reviewed (P44-49). The structure and function of the mechanical barrier, chemical barrier, microbial barrier, and immune barrier of the respiratory mucosa of poultry were reviewed (P50-52). In addition, the effect of high temperature boiled technology on the nutrient content of chicken was reviewed (P60-61). The purpose of the experiment is to study the feeding effects of Astragalus extract and Glycyrrhiza extract on broilers and their effects on intestinal health and respiratory health and to explore their potential mechanism of action. This research will supply a new type of antibiotic substitute in broiler feed, and provide a theoretical basis for the application of Astragalus extract and Glycyrrhiza extract in poultry production. The research content of the experiment includes the following parts: (1) Effects of Astragalus extract and Glycyrrhiza extract on production performance, nutrient metabolic rate, and meat quality of broilers; (2) Effects of Astragalus extract and Glycyrrhiza extract on immune function, antioxidant function and inflammatory factors in broilers; (3) Potential mechanisms of the effects of Astragalus extract and Glycyrrhiza extract on the intestinal barrier and respiratory tract barrier of broilers. (4) The effects of adding Astragalus extract and Glycyrrhiza extracts to broiler diets on meat quality traits of chicken meat treated by high temperature water boiling technology, such as color, shear strength, nutrient composition and fatty acid content. In the second part (P64-74), the experimental design is carried out according to the research topic of this paper. 720 1-day-old Arbor Acres broiler chickens were selected and randomly divided into 6 treatments with 6 replicates comprising 20 broilers each. All the animals were managed according to the guidelines for the care and use of experimental animals approved by The Ethics Committee of Henan Agricultural University (No. HNND2021031503). The control group (CON) was fed the basal diet without antibiotics, and the antibiotic group (ANT) was fed the basal diet supplemented with 500 mg/kg of Terramycin calcium, the Astragalus extract group (AE) was fed the basal diet supplemented with 300 mg/kg of Astragalus extract, the Glycyrrhiza extract group (GE) was fed the basal diet supplemented with Glycyrrhiza extract 150 mg/kg, Astragalus extract + Glycyrrhiza extract Ⅰ group (AE + GE Ⅰ) was fed the basal diet supplemented with Astragalus extract 300 mg/kg and Glycyrrhiza extract 150 mg/kg, Astragalus extract +Glycyrrhiza extract II group (AE+GE II) was fed the basal diet supplemented with Astragalus extract 150 mg/kg and Glycyrrhiza extract 75 mg/kg. The experimental diets were fed for 42 d. The three part (P76-117): by measuring the production performance such as body weight, average daily gain, average daily feed intake, and feed conversion rate of broilers, the results showed that the groups added with plant extracts improved the average daily weight gain and energy metabolic rate of broilers and decreased the feed-to-weight ratio, which was no different from the effect of adding antibiotic on the performance of broilers. The fatty acid content of the muscle was measured by gas chromatography, and the pH value, shear force, and muscle color of the muscle were also measured. The results showed that the groups added with the plant extract increased the content of polyunsaturated fatty acids in the muscle, and the effect was better than that of antibiotics. Enzyme-linked immunosorbent assay was used to determine the immune indexes, antioxidant indexes, and inflammatory factors in serum. The results showed that AE+GE Ⅰ group and AE+GE II group increased thymus index and serum IgA content, the GE group and the AE+GE group increased serum IgM content, AE group, GE group, and AE+GE Ⅰ group increased serum IgG content, AE+GE II group increased spleen index. The groups added with plant extracts increased the SOD content of the trachea. In addition, the AE group increased the serum T-AOC content, the GE group increased the serum SOD content, the AE group and the GE group increased the tracheal T-AOC content, The content of MDA in serum was decreased, and the content of GSH-Px in the trachea was increased in GE group and AE+GE II group. Adding Astragalus extract and Glycyrrhiza extract was more effective than Terramycin calcium in improving the immune function and antioxidant function of broilers. The levels of TNF-α and IL-6 in serum were decreased in each group supplemented with plant extracts, the levels of IL-1β in serum were decreased in the AE group, GE group, and AE+GE II group, and IL-1β and IL-6 content in lungs were decreased in GE group and AE+GE II group. Adding plant extracts was as effective in suppressing inflammation as adding antibiotics. The intestinal slices were made by hematoxylin-eosin staining, and the mucosal morphology of the intestinal tract was observed by electron microscope. The villus height and the ratio of villus height to crypt depth for adding plant extracts groups were higher than that of ANT. The expression of tight junction protein and mucin in intestinal mucosa was determined by microspectrophotometer, and the content of DAO in serum was determined by enzyme-linked immunosorbent assay. NRF2 mRNA expression in duodenum, jejunum, ileum and trachea, SOD1, SOD2, GSH-Px mRNA expression in the duodenum, SOD1, GSH-Px mRNA expression in the jejunum, SOD1, SOD2, GSH-Px mRNA in ileum were increased in each group supplemented with Astragalus extract and Glycyrrhiza extract, and the DAO content was decreased. The results showed that adding Astragalus extract and Glycyrrhiza extract was more effective than antibiotics in improving the intestinal antioxidant function and permeability of broilers. Using high-throughput sequencing to analyze the microbial abundance of cecal contents, the results showed that the addition of Astragalus extract and Glycyrrhiza extract increased the diversity and richness of intestinal microorganisms, improved the structure of intestinal flora, increased the beneficial bacteria, and decreased the harmful bacteria. The effect is better than antibiotics in improving intestinal flora. Correlation analysis showed that Astragalus extract and Glycyrrhiza extract had effects on production performance, serum antioxidant function, immune function, inflammatory factors, intestinal mucosal morphology, and intestinal permeability by improving the structure of intestinal flora. The meat quality traits of broilers were determined by the method of high temperature boiled. The results showed that the high temperature boiled technology could improve the meat quality traits of broilers fed with Astragalus extract and Glycyrrhiza extract. The fourth and fifth Parts (P119-139): based on the above research, the following conclusions are drawn: the addition of Astragalus extract and Glycyrrhiza extract in the diet improves the production performance, the apparent metabolic rate of energy, the meat quality, antioxidant and immune function in broilers, and improves the intestinal mucosal morphology, intestinal and respiratory barrier function, inhibits the occurrence of pro-inflammatory factors. In addition, the high temperature boiled technology can improve the meat quality traits of broilers fed with Astragalus extract and Glycyrrhiza extract. It is speculated that Astragalus extract and Glycyrrhiza extract can affect production performance, serum antioxidant performance, immune function, inflammatory factors, intestinal mucosal morphology, and intestinal permeability by improving the structure of intestinal flora. Astragalus extract and Glycyrrhiza extract can be used in poultry production as an alternative to antibiotics. Among them, the feeding effect of adding 150 mg/kg Astragalus extract + 75 mg/kg Glycyrrhiza extract group was the best, and the feeding effect of adding Glycyrrhiza extract alone was better than that of adding Astragalus extract alone. In addition, adding Glycyrrhiza extract alone has the best economic benefits. This paper is the first to systematically study the effects of Astragalus extract, and Glycyrrhiza extract and their combined use on production performance, meat quality, antioxidant function, immune function, and intestinal barrier function of broilers. For the first time, through the analysis of gut microbial diversity, the possible mechanism was investigated for the effects of Astragalus extract and Glycyrrhiza extract on broilers by regulating gut microbes. The effect of high temperature boiled technology on meat quality traits of broilers fed with Astragalus extract and Glycyrrhiza extract was studied for the first time. The results of the study provide a theoretical basis for the replacement of antibiotics with Astragalus extract and Glycyrrhiza extract and their application in broiler production and provide an effective way for safe broiler food production. In the future, we will further study the mechanism of Astragalus extract and Glycyrrhiza extract and their combined use on the respiratory barrier function of broilers, and on the intestinal microbial metabolic pathway of broilers. This project was supported by the Central Plains High Level Talent Special Program (Grant No. 204200510010). Professor Kyselov Oleksandr from Sumy Agrarian University in Ukraine and Professor Wang Zhixiang from Henan Agricultural University designed the experiment. Professor Liu Changzhong from Henan University of Science and Technology provided funding support. Qiao Yingying independently completed the experiment and wrote a manuscript for this degree thesis. Professor Kyselov Oleksandr and Professor Wang Zhixiang proposed revisions.