Antimicrobial growth promoters (AGPs) are commonly used in the livestock industry at subtherapeutic levels to improve production efficiency, which is achieved mainly through modulation of the intestinal microbiota. However, how different classes of AGPs, particularly ionophores, regulate the gut microbiota remains unclear. In this study, male Cobb broiler chickens were supplemented for 14 days with or without one of five commonly used AGPs including three classical antibiotics (bacitracin methylene disalicylate, tylosin, and virginiamycin) and two ionophores (monensin and salinomycin) that differ in antimicrobial spectrum and mechanisms. Deep sequencing of the V3-V4 region of the bacterial 16S rRNA gene revealed that two ionophores drastically reduced a number of rare bacteria resulting in a significant decrease in richness and a concomitant increase in evenness of the cecal microbiota, whereas three antibiotics had no obvious impact. Although each AGP modulated the gut microbiota differently, the closer the antibacterial spectrum of AGPs, the more similarly the microbiota was regulated. Importantly, all AGPs had a strong tendency to enrich butyrate- and lactic acid-producing bacteria, while reducing bile salt hydrolase-producing bacteria, suggestive of enhanced metabolism and utilization of dietary carbohydrates and lipids and improved energy harvest, which may collectively be responsible for the growth-promoting effect of AGPs.

Background: The emergence of antimicrobial resistance has necessitated the development of effective alternatives to antibiotics for livestock and poultry production. This study investigated a possible synergy between butyrate and forskolin (a natural labdane diterpene) in enhancing innate host defense, barrier function, disease resistance, growth performance, and meat quality of broilers. Methods: The expressions of representative genes involved in host defense (AvBD9 and AvBD10), barrier function (MUC2, CLDN1, and TJP1), and inflammation (IL-1β) were measured in chicken HD11 macrophages in response to butyrate and forskolin in the presence or absence of bacterial lipopolysaccharides (LPS). Intestinal lesions and the Clostridium perfringens titers were also assessed in C. perfringens-challenged chickens fed butyrate and forskolin-containing Coleus forskohlii (CF) extract individually or in combination. Furthermore, growth performance and carcass characteristics were evaluated in broilers supplemented with butyrate and the CF extract for 42 d. Results: Butyrate and forskolin synergistically induced the expressions of AvBD9, AvBD10, and MUC2 in chicken HD11 cells (P < 0.05) and the synergy was maintained in the presence of LPS. Butyrate and forskolin also suppressed LPS-induced IL-1β gene expression in HD11 cells in a synergistic manner (P < 0.05). The two compounds significantly reduced the intestinal lesions of C. perfringens-challenged chickens when combined (P < 0.05), but not individually. Furthermore, butyrate in combination with forskolin-containing CF extract had no influence on weight gain, but significantly reduced feed intake (P < 0.05) with a strong tendency to improve feed efficiency (P = 0.07) in a 42-d feeding trial. Desirably, the butyrate/forskolin combination significantly decreased abdominal fat deposition (P = 0.01) with no impact on the carcass yield, breast meat color, drip loss, or pH of d-42 broilers. Conclusions: Butyrate and forskolin has potential to be developed as novel antibiotic alternatives to improve disease resistance, feed efficiency, and carcass composition of broilers.

The rising concern of antimicrobial resistance highlights a need for effective alternatives to antibiotics for livestock production. Butyrate, forskolin, and lactose are three natural products known to induce the synthesis of host defense peptides (HDP), which are a critical component of innate immunity. In this study, the synergy among butyrate, forskolin, and lactose in enhancing innate host defense, barrier function, and resistance to necrotic enteritis and coccidiosis was investigated. Our results indicated that the three compounds synergistically augmented the expressions of multiple HDP and barrier function genes in chicken HD11 macrophages. The compounds also showed an obvious synergy in promoting HDP gene expressions in chicken jejunal explants. Dietary supplementation of a combination of 1 g/kg sodium butyrate, 10 mg/kg forskolin-containing plant extract, and 10 g/kg lactose dramatically improved the survival of chickens from 39% to 94% (p < 0.001) in a co-infection model of necrotic enteritis. Furthermore, the three compounds largely reversed growth suppression, significantly alleviated intestinal lesions, and reduced colonization of Clostridium perfringens or Eimeria maxima in chickens with necrotic enteritis and coccidiosis (p < 0.01). Collectively, dietary supplementation of butyrate, forskolin, and lactose is a promising antibiotic alternative approach to disease control and prevention for poultry and possibly other livestock species.

Background: Intestinal microbiota is critical for maintaining animal health and homeostasis. However, involvement of the fungal community, also known as the mycobiota, in animal health and disease is poorly understood. This study was aimed to examine the association between the intestinal mycobiota and the severity of necrotic enteritis (NE), an economically significant poultry disease. Methods: A total of 90 day-of-hatch Cobb broilers were infected with Eimeria maxima on d 10, followed by an oral challenge with C. perfringens on d 14 to induce NE, while another 10 broilers were served as mock-infected controls. On d 17, the lesions in the jejunum were scored, and the ileal digesta were subjected to DNA isolation and real-time PCR quantification of total bacterial and fungi populations. Internal transcribed spacer 2 (ITS2) amplicon sequencing was also performed to profile the ileal mycobiota composition. Changes in the ileal mycobiota in response to NE were investigated. Spearman correlation analysis was further conducted to identify the correlations between relative abundances of individual ileal fungi and the severity of NE. Results: While the total bacterial population in the ileum was increased by 2- to 3-fold in NE chickens, the total fungal population was progressively declined in more exacerbated NE, with the most severely infected chickens showing a nearly 50-fold reduction relative to mock-infected controls. Richness of the ileal mycobiota also tended to reduce in chickens with NE (P = 0.06). Compositionally, among 30 most abundant fungal amplicon sequence variants (ASVs), 11 were diminished and 7 were enriched (P < 0.05), while 12 remained largely unchanged in NE-afflicted chickens (P > 0.05). Multiple Wallemia and Aspergillus species were markedly diminished in NE (P < 0.05) and also showed a significant negative correlation with NE severity (P < 0.05). Conclusions: Dysbiosis of the ileal mycobiota is induced evidently by NE and the extent of the dysbiosis is positively correlated with disease severity. These findings suggest a possible role of the intestinal mycobiota in NE pathogenesis and highlight the mycobiota as a new potential target for NE mitigation in poultry.