Misuse of synthetic antibiotics in livestock leads to the transfer of antibiotic resistant pathogens into humans and deposits toxic residues in meat and milk. There is therefore an urgent need for safe and viable alternative approaches to improve the nutrition and wellbeing of farm animals. An alternative source that has been widely exploited is traditional Chinese herbal medicine (TCHM). These herbal medicines are an important part of the healthcare system in many Asian countries. Such herbs contain several but less toxic bioactive compounds which are generally regarded biodegradable. Recently, advances in knowledge on the importance of TCHM have led to a rapid increase in its production and hence, increasing the amount of by-products generated. Such by-products have become a serious environmental challenge because producers regard them as industrial waste and discard them directly. Incorporating TCHM by-products as feed additives to improve animal health and nutrition has been proposed because they contain high amounts of bioactive compounds which confer several health benefits to animals. TCHM by-products as feed additives apart from being a good alternative for synthetic antibiotics could also minimize the current environmental challenges associated with its disposal. This review summarizes scientific findings on the bioactive compounds in TCHM and TCHM by-products, discusses functional dietary patterns and outlines challenges that may hinder full utilization of TCHM by-products in animal production.

: The gastro intestinal tract (GIT) of humans and animals is host to a complex community of different microorganisms whose activities significantly influence host nutrition and health through enhanced metabolic capabilities, protection against pathogens, and regulation of the gastrointestinal development and immune system. New molecular technologies and concepts have revealed distinct interactions between the gut microbiota and dietary amino acids (AAs) especially in relation to AA metabolism and utilization in resident bacteria in the digestive tract, and these interactions may play significant roles in host nutrition and health as well as the efficiency of dietary AA supplementation. After protein is digested and AAs and peptides are absorbed in the small intestine, significant levels of endogenous and exogenous nitrogenous compounds enter the large intestine through the ileocaecal junction. Once in the colonic lumen, these compounds are not markedly absorbed by the large intestinal mucosa, but undergo intense proteolysis by colonic microbiota leading to the release of peptides and AAs and results in production of numerous bacterial metabolites such as ammonia, amines, short chain fatty acids (SCFAs), branched-chain fatty acids (BCFAs), hydrogen sulfide, organic acids, and phenols. These metabolites influence various signaling pathways in epithelial cells, regulate the mucosal immune system in the host, and modulate gene expression of bacterial which results in the synthesis of enzymes associated with AA metabolism. This review aims to summarize the current literature relating to how the interactions between dietary amino acids and gut microbiota may promote host nutrition and health.

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This study was conducted to investigate the effects of Astragalus by-product (ABP) through dietary supplementation at different levels on performance, nutrient digestibility, rumen fermentation, blood metabolites, and immune response in sheep. Twenty-four Doper × Small Tail Han ewes (6-7 months of age; 29.07 ± 2.28 kg initial body weight) were randomly assigned to one of three treatments for a 47 d feeding period. Treatments consisted of the sheep diet supplemented with 0% ABP-control, 10% ABP, or 15% ABP of the diet (dry matter basis). Blood samples were collected on days 0, 15, 30, and 45 of the feeding period. APB supplementation did not affect growth performance and apparent digestibility of organic matter, crude protein, and acid detergent fibre (P>0.05). However, ether extract digestibility was decreased in the 10% ABP group and increased in the 15% ABP group (P<0.001), and both 10% ABP and 15% ABP decreased the neutral detergent fibre digestibility (P=0.005). Feeding ABP increased rumen pH (P<0.001) and ammonia N (P<0.001) and decreased concentrations of acetate (P=0.007) and propionate (P=0.001) which resultantly increased the acetate-to-propionate ratio (P<0.001) in ruminal fluid. There were no interaction effects between treatment and sampling time for plasma metabolites and immunity (P>0.05). However, inclusion of dietary 10% ABP decreased concentrations of plasma cholesterol (P=0.043). Also, plasma concentrations of low-density lipoprotein decreased on days 30 and 45 (P=0.017) of the feeding period. Metabolite concentrations of total protein, albumin, globulin, blood urea N, glucose, triglyceride, and high-density lipoprotein cholesterol and humoral immune indicators were not affected (P>0.05) by dietary ABP supplementation. The results suggest that ABP could be reclaimed through dietary inclusion in animal feed since it had beneficial effects on rumen fermentation patterns and lipid metabolism and had no adverse effects on performance and humoral immunity in sheep.