Effects of dietary supplementation of synthetic antimicrobial peptide-A3 and P5 on growth performance, apparent total tract digestibility of nutrients, fecal and intestinal microflora and intestinal morphology in weanling pigs

Effects of cecropin antimicrobial peptides on growth and intestinal health in growing male minks

This study investigated the effects of dietary supplementation with cecropin antimicrobial peptides (CAD) on growth performance and intestinal health in growing male minks (Neovison vison). A cohort of 60 male minks (65 days old) were evenly divided into six groups and fed a basal diet supplemented with CAD at 0 (control), 100, 200, 300, 400, or 500 mg/kg for 8 weeks. The findings revealed that the minks in 200 mg/kg CAD group had greater growth performance, with significantly higher final body weight (FBW) and average daily gain (ADG). Compared to the minks in the control (p < 0.05). Digestibility analyses at week 3 demonstrated that CAD supplementation enhanced ether extract (EE) digestibility (p < 0.05), while 200, 400, and 500 mg/kg CAD improved crude protein (CP) digestibility (p < 0.05). Intestinal morphology assessments indicated that 200 mg/kg CAD significantly increased duodenal and jejunal villus height (both p < 0.05) and jejunal villus height-to-crypt depth ratio (p < 0.05) compared to the control. Serum immunological analyses revealed elevated levels of complement C4 and IgG in CAD-supplemented groups (p < 0.05). Notably, the 100 mg/kg CAD group exhibited the higher serum IgA, IgM, and complement C3, and less jejunal TNF-α levels (all p < 0.05). Microbiota profiling showed that CAD supplementation reduced the relative abundance of Escherichia-Shigella and Mycoplasma, while 100, 200 and 400 mg/kg CAD decreased Peptostreptococcaceae populations (p < 0.05). The 100 mg/kg CAD group displayed optimal immune enhancement and microbiota modulation, whereas the 200 mg/kg group achieved the best growth performance and intestinal function. These results suggest that dietary CAD supplementation at 100-200 mg/kg effectively improves growth, nutrient utilization, and intestinal health in growing male minks.

Effects of dietary ε-polylysine supplementation on growth performance, antioxidant capacity, immune function, and intestinal microbiota in growing male minks

Introduction

This study investigated the effects of dietary ε-polylysine (ε-PL) supplementation on the growth performance, antioxidant capacity, immune function and intestinal microbiota in growing male minks.

Methods

Ninety-six 12-week-old male minks were randomly divided into 6 treatments (8 replicates per treatment and 2 minks per replicate). Minks were fed basal diets supplemented with 0 (control), 100, 200, 300, 400, or 500 mg/kg ε-PL for 8 weeks.

Results

Compared with the control, 300-500 mg/kg ε-PL significantly increased the average daily gain (p < 0.05), and significantly decreased the feed-to-gain ratio (p < 0.05) during the whole period and significantly enhanced the body weight at week 8 (p < 0.05), 300-400 mg/kg ε-PL significantly increased the fresh pelt weight (p < 0.05). Compared with the control, 300 mg/kg ε-PL significantly increased serum T-SOD activity and jejunal mucosal T-SOD and GSH-Px activities (p < 0.05). Compared to the control, 200-400 mg/kg ε-PL significantly increased serum IgA level (p < 0.05), 300-400 mg/kg ε-PL significantly increased serum IgM level (p < 0.05), 400-500 mg/kg ε-PL significantly increased serum IgG level (p < 0.05). Compared with the control, 200-400 mg/kg ε-PL significantly increased jejunal mucosal IgA level (p < 0.05), 100 mg/kg ε-PL significantly increased jejunal mucosal IgM level (p < 0.05), 100-400 mg/kg ε-PL significantly increased jejunal mucosal IgG level (p < 0.05). Compared with the control group, all ε-PL supplemented groups significantly decreased serum IL-2 and IL-8 levels compared to the control (p < 0.05). The 16S rRNA sequencing analysis revealed that compared to the control, 300 mg/kg ε-PL significantly increased the relative abundance of Firmicutes and Clostridium_sensu_stricto_1 (p < 0.05), and significantly decreased the relative abundance of Proteobacteria and Escherichia-Shigella in ileal mucosa (p < 0.05). Spearman correlation analysis indicated that the relative abundance of Escherichia-Shigella was negatively correlated with the growth performance. The relative abundance of Clostridium_sensu_stricto_1 was positively correlated with the jejunal mucosal antioxidant indicators and immunoglobulin levels.

Discussion

In conclusion, dietary ε-PL supplementation can improve growth performance, antioxidant capacity, immune function, and gut microbial community in growing male minks, and the optimal dosage of ε-PL is 300 mg/kg.

Dietary supplementation with antibacterial peptide microcin J25 improved antioxidant capacity and intestinal health of pigeons

Introduction

The present study aimed to evaluate the potential of antimicrobial peptide microcin J25 (MccJ25) as a feed additive for pigeons.

Methods

A total of 28-day-old pigeons were allocated to four groups and fed a basal diet (CON) or a basal diet supplemented with 100, 200, or 300 mg/kg MccJ25 (ABP100, ABP200, and ABP300) for 8 weeks.

Results

Dietary MccJ25 supplementation significantly improved survival rates in the ABP200 group compared to the control (p < 0.05). Serum analysis revealed that ABP200 and ABP300 groups exhibited increased levels of total protein (TP), globulin (GLB), immunoglobulin A (IgA), and immunoglobulin G (IgG), alongside reduced aspartate aminotransferase (AST), alanine aminotransferase (ALT), total cholesterol (TC), and triglyceride (TG) concentrations (p < 0.05). Furthermore, MccJ25 supplementation enhanced duodenal maltase and trypsin activity (p < 0.05) and upregulated intestinal and hepatic antioxidant capacity, as evidenced by elevated glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activity (p < 0.05). Intestinal morphology improvements were observed in the jejunum and ileum, with increased villus height-to-crypt depth ratios (VH/CD) (p < 0.05). Additionally, ABP200 and ABP300 groups demonstrated significant upregulation of intestinal barrier-related genes occludin (OCLN), claudin 1 (CLDN1), zonula occluden protein 1 (ZO1), mucin 2 (MUC2), superoxide dismutase 1, 2 (SOD1, 2), and catalase (CAT) in duodenum (p < 0.05).

Discussion

These findings indicate that MccJ25 supplementation improves systemic metabolism, enhances antioxidant defenses, strengthens intestinal barrier integrity, and ultimately promotes pigeon health and survival. This study supports the application of MccJ25 as a functional feed additive in poultry production.

Development strategies and application of antimicrobial peptides as future alternatives to in-feed antibiotics

The use of in-feed antibiotics has been widely restricted due to the significant environmental pollution and food safety concerns they have caused. Antimicrobial peptides (AMPs) have attracted widespread attention as potential future alternatives to in-feed antibiotics owing to their demonstrated antimicrobial activity and environment friendly characteristics. However, the challenges of weak bioactivity, immature stability, and low production yields of natural AMPs impede practical application in the feed industry. To address these problems, efforts have been made to develop strategies for approaching the AMPs with enhanced properties. Herein, we summarize approaches to improving the properties of AMPs as potential alternatives to in-feed antibiotics, mainly including optimization of structural parameters, sequence modification, selection of microbial hosts, fusion expression, and industrially fermentation control. Additionally, the potential for application of AMPs in animal husbandry is discussed. This comprehensive review lays a strong theoretical foundation for the development of in-feed AMPs to achieve the public health globally.

Dietary and Therapeutic Benefits of Edible Insects: A Global Perspective

Edible insects are gaining traction worldwide for research and development. This review synthesizes a large and well-established body of research literature on the high nutritional value and variety of pharmacological properties of edible insects. Positive benefits of insect-derived products include immune enhancement; gastrointestinal protection; antitumor, antioxidant, and anti-inflammatory capacities; antibacterial activities; blood lipid and glucose regulation; lowering of blood pressure; and decreased risk of cardiovascular diseases. However, the pharmacological mechanisms of these active components of edible insects in humans have received limited research attention. In addition, we discuss health risks (safety); application prospects; regulations and policies governing their production and consumption with a view to promote innovations, intraglobal trade, and economic development; and suggestions for future directions for further pharmacological functional studies. The aim is to review the current state of knowledge and research trends on edible insects as functional ingredients beneficial to the nutrition and health of humans and animals (livestock, aquatic species, and pets).

Effects of Broad Bean Diet on the Growth Performance, Muscle Characteristics, Antioxidant Capacity, and Intestinal Health of Nile Tilapia (Oreochromis niloticus)

Four crisping diets were designed to conduct a feeding experiment to investigate the use of broad bean in the formulated feed of Nile tilapia and optimize its use. The growth performance, muscle characteristics, antioxidant capacity, and intestinal health of Nile tilapia with an initial body weight of 617.32 ± 1.64 g were evaluated after being fed with different diets for 90 days. The results showed no adverse effect on the growth performance of Nile tilapia fed with broad bean diets. Contrastingly, some improvements were found in WGR and SGR, but a lower FCR was obtained. The supplementation of broad beans weakened the antioxidant capacity of fish but did not influence liver health and the immune system. Increasing the amount of broad bean addition can increase muscle quality values, and an embrittling functional package being added to the diet can also improve muscle hardness, adhesiveness, and chewiness of Nile tilapia muscle. In addition, the crisping functional package can be applied to tilapia crisping formulated feed, which helps to improve the integrity of the intestinal tissue structure and optimize the intestinal microbiota of Nile tilapia. The final achievement of this study is to provide a theoretical reference for optimizing the breeding technology of crispy Nile tilapia and developing a specialized crisping diet for the species.

Effects of maggot antimicrobial peptides on growth performance, immune function, and cecal flora of yellow-feathered broilers

INTRODUCTION

This study investigated the effects of maggot antimicrobial peptides on growth performance, blood parameters, immune organ index, and cecum microbial diversity in yellow broilers.

METHODS

The addition of 100-300 mg/kg maggots antimicrobial peptides to the corn-soybean meal basal diet was evaluated. Two hundred and forty one-day-old yellow-feathered broilers were randomly divided into four groups (60 chickens in each group): basal diet group (BC group), basal diet group + 100, 200, 300 mg/kg maggots antimicrobial peptides (MDAL group, MDAM group, and MDAH group).

RESULTS

The result showed that the average daily feed intake (ADFI) of the BC group, MDAM group, and MDAH group was higher than that of the MDAL group (P > 0.05), the average daily gain of MDAM group and MDAH group was significantly higher than that of BC group and MDAL group (P < 0.05), but the feed-weight ratio (F/G) was significantly lower than that of BC group (P < 0.05). The total protein (TP) content in the MDAM group and MDAH group was significantly higher than that in the BC group (P < 0.05), and the albumin (ALB) content in the MDAH group was higher than that in the BC group (P > 0.05). The contents of IgA and IgG in the MDAH group were significantly higher than those in the BC group (P < 0.05). In contrast, the content of alanine aminotransferase (ALT) in the MDAH group was significantly lower than that in the BC group (P < 0.05). The thymus and spleen indexes of the MDAH group were significantly higher than those of the BC group (P < 0.05). 16S rDNA sequencing results showed that Bacteroidota and Bacteroides were the dominant phylum and genus of cecal microorganisms at the phylum and genus levels, respectively. Cecum microorganisms are mainly involved in biological processes such as energy production and conversion, amino acid transport and metabolism, and carbohydrate transport and metabolism.

DISCUSSION

It was concluded that adding different doses of maggot antimicrobial peptide to the basal diet could improve yellow-feathered broilers' growth and immune performance and change the cecum flora. The appropriate dose of antimicrobial peptide addition was 300 mg/kg.

Bioactive Peptide Discovery from Edible Insects for Potential Applications in Human Health and Agriculture

In the past decade, there has been fast-growing interest among researchers to discover bioactive peptides from edible insects and to evaluate their potential applications in the management of human, livestock, and plant health. This review summarizes current knowledge of insect-derived peptides and their potential role in tackling human health issues and solving agriculture problems by protecting crops and livestock against their pathogens. Numerous bioactive peptides have been identified from edible insect species, including peptides that were enzymatically liberated from insect proteins and endogenous peptides that occur naturally in insects. The peptides exhibited diverse bioactivities, encompassing antioxidant, anti-angiotensin-converting enzyme, anti-dipeptidyl peptidase-IV, anti-glucosidase, anti-lipase, anti-lipoxygenase, anti-cyclooxygenase, anti-obesity, and hepatoprotective activities. Such findings point to their potential contribution to solving human health problems related to inflammation, free radical damage, diabetes, hypertension, and liver damage, among others. Although most of the experiments were performed in vitro, evidence for the in vivo efficacy of some peptides is emerging. Evidence of the protective effects of insect-derived endogenous antimicrobial peptides in combating farm animal and plant pathogens is available. The ability of insect-derived endogenous neuropeptides to protect plants against herbivorous insects has been demonstrated as well. Nevertheless, the potency of peptides identified from insect protein hydrolysates in modulating livestock and plant health remains a knowledge gap to be filled.

Available for millions of years but discovered through the last decade: Insects as a source of nutrients and energy in animal diets

The aim of this review is to present and discuss the most recent literature about the processing of insect biomass and its impact on nutritive value, further implementation of meals and fats derived from invertebrates to livestock (poultry and swine), aquaculture (salmonids), and companion animal diets and their impact on growth performance, metabolic response, and gastrointestinal microbiota shifts. Additionally, the most important barriers to obtaining unified products in terms of their nutritive value are considered, i.e., to define insects' nutrient requirements, including various technological groups and further biomass processing (slaughtering, drying, and storage). Due to the current limitation in the insect production process consisting of the lack of infrastructure, there is stress on the relatively small amount of insect products added to the animal diets as a functional feed additive. Currently, only in the case of pet nutrition may insects be considered a full replacement for commonly used environmentally harmful and allergenic products. Simultaneously, the least information has been published on this topic. Thus, more scientific data are needed, particularly when the pet food branch and insect-based diets are rapidly growing.

Dietary Antimicrobial Peptides Improve Intestinal Function, Microbial Composition and Oxidative Stress Induced by Aeromonas hydrophila in Pengze Crucian Carp (Carassius auratus var. Pengze)

There is increasing evidence for the potential use of antimicrobial peptides as dietary supplements and antibiotic substitutes. In this study, we analyzed the differential effects of varying levels of antimicrobial peptides on the intestinal function and intestinal microbial and disease resistance of Pengze crucian carp. Approximately 630 experimental fishes were randomized in the control group (G0: 0 mg/kg) and in five groups supplemented with different doses of AMPs (G1: 100 mg/kg, G2: 200 mg/kg, G3: 400 mg/kg, G4: 800 mg/kg, and G5: 1600 mg/kg) and were fed for ten weeks. Three replicates per group of 35 fish were performed. The results showed that AMPs promoted intestinal villus development and increased intestinal muscular thickness (p < 0.05) and goblet cell abundance. The enzymatic activities of all groups supplemented with AMPs were effectively improved. AMP supplementation significantly enhanced the activities of antioxidant enzymes and digestive enzymes in the intestines of G3 animals (p < 0.05). Compared with G0 animals, AMP-supplemented animals regulated the expression of intestinal immune-related genes and exhibited significant differences in the G3 animal group (p < 0.05). The abundance of intestinal Firmicutes and Bacteroidetes increased in the AMP-supplemented groups, but the Firmicutes/Bacteroidetes ratio was lower than that in the G0 group. AMP supplementation also decreased the abundance of Fusobacterium while increasing the proportion of Actinobacteria (p < 0.05). After Aeromonas hydrophila infection, the expression levels of anti-inflammatory factors in the intestinal tract of G3 animals were significantly upregulated, and the level of the proinflammatory factor was decreased (p < 0.05). The intestinal Cetobacterium levels of G3 animals were significantly increased (p < 0.01), while the Proteobacteria levels were decreased, and the intestinal goblet cell proliferation was significantly lower than that of G0 animals (p < 0.05). This indicates that groups supplemented with AMPs have better disease resistance than the G0 group and can rapidly reduce the adverse effects caused by inflammatory response. Taken together, the present results suggest that AMP supplementation can improve intestinal function and intestinal microbial and pathogen resistance in Pengze crucian carp.

Antimicrobial Peptides Controlling Resistant Bacteria in Animal Production

In the last few decades, antimicrobial resistance (AMR) has been a worldwide concern. The excessive use of antibiotics affects animal and human health. In the last few years, livestock production has used antibiotics as food supplementation. This massive use can be considered a principal factor in the accelerated development of genetic modifications in bacteria. These modifications are responsible for AMR and can be widespread to pathogenic and commensal bacteria. In addition, these antibiotic residues can be dispersed by water and sewer water systems, the contamination of soil and, water and plants, in addition, can be stocked in tissues such as muscle, milk, eggs, fat, and others. These residues can be spread to humans by the consumption of water or contaminated food. In addition, studies have demonstrated that antimicrobial resistance may be developed by vertical and horizontal gene transfer, producing a risk to public health. Hence, the World Health Organization in 2000 forbid the use of antibiotics for feed supplementation in livestock. In this context, to obtain safe food production, one of the potential substitutes for traditional antibiotics is the use of antimicrobial peptides (AMPs). In general, AMPs present anti-infective activity, and in some cases immune response. A limited number of AMP-based drugs are now available for use in animals and humans. This use is still not widespread due to a few problems like in-vivo effectiveness, stability, and high cost of production. This review will elucidate the different AMPs applications in animal diets, in an effort to generate safe food and control AMR.

Effects of Immobilized Antimicrobial Peptides on Growth Performance, Serum Biochemical Index, Inflammatory Factors, Intestinal Morphology, and Microbial Community in Weaning Pigs

This experiment was conducted to investigate the effects of immobilized antimicrobial peptides on growth performance, serum biochemical index, inflammatory factors, intestinal morphology, and microbial community of weaning piglets. A total of 21 weaning piglets [Duroc × (Landrace × Yorkshire)] with initial body weight (7.64 ± 0.65 kg) were randomly allocated to one of three treatments with seven replicates (one pig per replicate) per treatment according to sex and weight in randomized complete block design. Pigs in the three treatments were fed corn–soybean meal-based diet (CON), corn–soybean meal based diet + flavomycin (25 mg/kg) + quinone (50 mg/kg) (AB), and corn–soybean meal based diet + 1,000 mg/kg immobilized antimicrobial peptides (IAMPs), respectively. The experiment lasted for 28 days, including early stage (0–14 days) and late stage (15–28 days). The results showed the following: (1) compared with the CON group, the average daily gain in the whole experimental time (p < 0.05) was significantly increased, and the diarrhea rate of weaning piglets was decreased (p < 0.01) in the IAMPs group; (2) compared with the CON group, the concentrations of serum IgM and superoxide dismutase (SOD) in the IAMPs group were significantly higher than the CON and AB groups (p < 0.01); (3) compared with CON group, the concentrations of serum interleukin (IL)-10 and transforming growth factor (TGF-β) were significantly increased (p < 0.05), and the concentration of IL-12 was significantly decreased (p < 0.05) in the IAMPs group; (4) compared with CON group, the concentrations of serum endotoxin and D-lactate of piglets were significantly reduced (p < 0.05), and the relative expression of ZO-1 and occludin in the jejunum of piglets were significantly increased (p < 0.05) in the IAMPs group; (5) compared with the CON group, the villus height of the duodenum and jejunum of weaning piglets in IAMPs and AB groups was significantly increased (p < 0.05); and (6) compared with CON group, the relative abundance of Escherichia–Shigella in the colon and cecal digesta was decreased. In summary, the addition of 1,000 mg/kg immobilized antimicrobial peptides in the diet effectively relieved weaning stress by showing improved growth performance, antioxidant and immune capacity, intestinal morphology, and microorganisms.

Investigating the effects of peptide-based, MOS and protease feed additives on the growth performance and fecal microbial composition of weaned pigs

Background

Digestive disorders in weaning pigs remain a major challenge for swine producers. Different types of commercial feed additives have been developed to promote gut health and development in young pigs, but their effects on resident gut microbial communities remain largely unexplored. The aim of this study was to investigate the impact of a peptide-based product (Peptiva) in combination with mannose oligosaccharides (MOS) and an exogenous protease on the performance and fecal microbiome of nursery pigs.

Methods

A total of 1097 weaned pigs were divided into 44 pens (24–26 pigs/pen) with each pen randomly assigned to one of four experimental diets as part of Phase II and Phase III of a standard nursery phase feeding program. Fecal samples collected from representative control and treatment pigs were used to investigate bacterial composition profiles by high throughput sequencing of PCR-generated amplicons targeting the V1-V3 region of the 16S rRNA gene.

Results

Higher gain:feed was observed for pigs fed Peptiva and MOS compared to Controls during the period when experimental diets were fed, but the benefits of supplementation were not maintained after pigs were transitioned to a non-supplemented diet. Three candidate bacterial species, identified as Operational Taxonomic Units (OTUs), were found to have significantly different abundances between control samples and treatment samples during the same phase. In Phase III samples, SD_Ssd-00039, predicted to be a strain of Streptococcus alactolyticus based on nucleotide sequence identity, was the most highly represented of these OTUs with an average abundance in pigs fed Peptiva, MOS and protease that was 3.9 times higher than in Controls. The report also presents evidence of microbial succession that occurred during the trial, with 16 of the 32 most abundant OTUs found to vary between Phase II and Phase III samples for the same dietary treatment.

Conclusions

Dietary supplementation with a combination of a peptide-based product, MOS, and protease increased the growth performance of weaned pigs compared to control animals during the nursery phase, but these benefits were no longer observed within 2 weeks after all animals were transitioned to a non-supplemented diet. Supplementation with these feed additives was found to modulate the composition of the swine gut microbiome during this period.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00681-8.

Effects of Antimicrobial Peptides Gal-13 on the Growth Performance, Intestinal Microbiota, Digestive Enzyme Activities, Intestinal Morphology, Antioxidative Activities, and Immunity of Broilers

To evaluate the application effect of antimicrobial peptides Gal-13 (AMP Gal-13) instead of antibiotic feed additives, 90 7-day-old Ross 308 broilers were randomly divided into 3 groups. Group A was fed a basic diet as the control, and Groups B and C were supplemented with AMP Gal-13 (100 mg/kg and 200 mg/kg, respectively). After a 35-day feeding experiment, the weight and average daily gain (ADG) of the broilers in Group B were significantly higher than those of the broilers in Group A. The Enterococcus sp. and Escherichia coli counts in the ileum and cecum in Group A were significantly higher than those in Groups B and C, while the Lactic acid bacteria (LAB) and Bifidobacterium sp. counts were significantly lower. The amylase activity of the jejunum in Group B was significantly higher than that in Group A. The villus length (VL): crypt depth (CD) ratios of the jejunum and ileum in Group B were significantly higher than those in Group A. The glutathione peroxidase (GSH-Px) activities in the liver and serum in Groups B and C were significantly higher than those in Group A, while the malondialdehyde (MDA) activity was significantly lower. The titers of Newcastle disease virus (NDV)-specific antibodies were elevated significantly in Group B at the age of 42 days. Additionally, the weights of the spleen and thymus were significantly increased. The expression levels of Il-2, Il-6, Tgf-β4, Tnf-α, and Mif in the spleen in Groups B and C were significantly downregulated to different degrees; Il-4 expression in Group B was significantly upregulated, while Ifn-γ expression in Group C was significantly upregulated. The results suggested that adding AMP Gal-13 to the diet could improve intestinal digestion, the antioxidant capacity, and immune function, ultimately promoting the growth of broilers.

Antimicrobial peptides as a feed additive alternative to animal production, food safety and public health implications: An overview

In the last few years, feed additives have been used in animal nutrition to improve nutrient utilization, health parameters and animal performance. However, the use of antibiotics as feed additives has allowed the occurrence of antimicrobial resistance (AMR), which can bring as a consequence, an increase in the morbidity and mortality of diseases that were previously treatable with antibiotics. In this context, antimicrobial peptides (AMP) have appeared as a promising strategy because they have multiple biological activities and represent a powerful strategy to prevent the development of resistant microorganisms. Despite the small number of studies applied in vivo, AMP appear as a potent alternative to the use of antibiotics in animal nutrition, due to an increase in feed efficiency and the prevention/treatment of some animal diseases. This review discusses the problems associated with antimicrobial resistance and the use of AMP as a strong candidate to replace conventional antibiotics, mainly in the animal industry.

Antimicrobial peptides used as growth promoters in livestock production

Antibiotic growth promoters (AGPs) have been administered in livestock for decades to improve food digestion in growing animals, while also contributing to the control of microbial pathogens. The long-term and indiscrimate use of AGPs has generated genetic modifications in bacteria, leading to antimicrobial resistance (AMR), which can be disseminated to commensal and pathogenic bacteria. Thus, antimicrobial peptides (AMPs) are used to replaced AGPs. AMPs are found in all domains of life, and their cationic characteristics can establish electrostatic interactions with the bacterial membrane. These molecules used as growth promoters can present benefits for nutrient digestibility, intestinal microbiota, intestinal morphology, and immune function activities. Therefore, this review focuses on the application of AMPs with growth promoting potential in livestock, as an alternative to conventional antibiotic growth promoters, in an attempt to control AMR. KEY POINTS: • The long-term and indiscriminate use of AGPs in animal food can cause AMR. • AMPs can be used as substitute of antibiotics in animal food suplementation. • Animal food suplementated with AMPs can provied economic efficiency and sustainable livestock production.

The Evaluation of UPro as a New Nutrient on High-Quality Egg Production From the Perspective of Egg Properties, Intestinal Histomorphology, and Oviduct Function of Laying Hens

This study was to investigate the effects of UPro as a new nutritive fortifier on high-quality egg production from the perspective of egg properties, intestinal histomorphology, and oviduct function of laying hens. Four hundred thirty-two Hy-Line Brown laying hens aged 56 weeks were allocated to four groups. Layers were given a basal diet or supplemented with different levels of small peptides (0.2, 0.4, and 0.8%) to replace soybean meal. After 1-week adaptation period, the feeding trial was conducted for 12 weeks. The results showed that UPro addition significantly decreased (P < 0.05) the hardness, stickiness, and chewiness of albumen of layers on weeks 12. A linear elevation (P < 0.05) in the albumen height, Haugh unit (HU), and crude protein content of albumen of layers were noted on week 12 along with dietary UPro addition increasing, and the villus height (VH) and villus height-to-crypt depth radio (VCR) of jejunum also linearly increasing (P < 0.05). In addition, there were linear elevations (P < 0.05) in the relative mRNA expression of Sec23 homolog A (Sec23A) and protein-O-mannosyltransferase1 (POMT1) in layers as dietary UPro addition increased. In conclusion, dietary UPro addition could improve intestinal health, increase the absorption of nutrients, and improve egg quality of laying hens. The possible mechanism underlying UPro improving the quality and processing characteristics of albumen is up-regulating Sec23A and POMT1 expression of magnum. These findings will promote the application of UPro as a new nutritional additive in the production of high-quality eggs.

Reducing the Risk of Transmission of Critical Antimicrobial Resistance Determinants From Contaminated Pork Products to Humans in South-East Asia

Antimicrobial resistance (AMR) is a critical challenge worldwide as it impacts public health, especially via contamination in the food chain and in healthcare-associated infections. In relation to farming, the systems used, waste management on farms, and the production line process are all determinants reflecting the risk of AMR emergence and rate of contamination of foodstuffs. This review focuses on South East Asia (SEA), which contains diverse regions covering 11 countries, each having different levels of development, customs, laws, and regulations. Routinely, here as elsewhere antimicrobials are still used for three indications: therapy, prevention, and growth promotion, and these are the fundamental drivers of AMR development and persistence. The accuracy of detection of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARG) depends on the laboratory standards applicable in the various institutes and countries, and this affects the consistency of regional data. Enterobacteriaceae such as Escherichia coli and Klebsiella pneumoniae are the standard proxy species used for indicating AMR-associated nosocomial infections and healthcare-associated infections. Pig feces and wastewater have been suspected as one of the hotspots for spread and circulation of ARB and ARG. As part of AMR surveillance in a One Health approach, clonal typing is used to identify bacterial clonal transmission from the production process to consumers and patients - although to date there have been few published definitive studies about this in SEA. Various alternatives to antibiotics are available to reduce antibiotic use on farms. Certain of these alternatives together with improved disease prevention methods are essential tools to reduce antimicrobial usage in swine farms and to support global policy. This review highlights evidence for potential transfer of resistant bacteria from food animals to humans, and awareness and understanding of AMR through a description of the occurrence of AMR in pig farm food chains under SEA management systems. The latter includes a description of standard pig farming practices, detection of AMR and clonal analysis of bacteria, and AMR in the food chain and associated environments. Finally, the possibility of using alternatives to antibiotics and improving policies for future strategies in combating AMR in a SEA context are outlined.

Effects of Dietary Supplementation of Recombinant Plectasin on Growth Performance, Intestinal Health and Innate Immunity Response in Broilers

The present study was conducted to evaluate the effects of dietary supplementation of recombinant plectasin (Ple) on the growth performance, intestinal health, and serum immune parameters in broilers. A total of 288 1-day-old male broilers (Arbor Acres) were randomly allotted to four dietary treatments including the basal diet (NC) and basal diet supplemented with 10 mg enramycin/kg (PC), 100 mg Ple/kg (LPle), and 200 mg Ple/kg (HPle) diets. The results indicated Ple increased (P < 0.01) average daily gain and decreased (P ≤ 0.02) feed to gain ratio of broilers. In addition, the supplementation of Ple in the diets increased (P ≤ 0.01) duodenal lipase (day 21) and trypsin (day 42) activities compared with the NC group. Similar as the supplementation of enramycin, Ple also increased villus height and decreased crypt depth in jejunum (day 21), and thus the villus height to crypt depth ratio (P < 0.01) was increased compared to the NC group on day 42. The serum immunoglobulin M (days 21 and 42), immunoglobulin G (day 42), complement 3 (day 21), and complement 4 (days 21 and 42) were significantly increased (P ≤ 0.02) due to the supplementation of Ple and enramycin, while the concentration of malondialdehyde in jejunum was decreased (P < 0.01) in PC, LPle, and HPle groups on day 21 compared with those in the NC group. Furthermore, Ple reduced (P < 0.01) Escherichia coli and total aerobic bacteria population in ileum and cecum of birds on days 21 and 42. These results indicate that the recombinant plectasin has beneficial effects on growth performance, intestinal health, and innate immunity in broilers.

Overall assessment of antimicrobial peptides in piglets: a set of meta-analyses

Developing alternatives to antibiotics is an urgent need in livestock production. Antimicrobial peptides (AMPs) are regarded as powerful antibiotic substitutes (ASs) because AMPs have broad-spectrum antimicrobial activities and growth-promoting ability. Here, we aimed to comprehensively assess the effects of AMPs on the growth performance, diarrhea rate, intestinal morphology and immunity of healthy or challenged piglets, compared with an antibiotics group or negative control group. We performed a set of meta-analyses of feeding trials from database inception to 27 May 2019. Among the 1379 identified studies, 20 were included in our meta-analyses (56 arms and 4067 piglets). The meta-analyses revealed that (1) compared with the negative control group, AMPs significantly improved the healthy piglets' average daily gain (ADG), average daily feed intake (ADFI), gain : feed ratio (G/F), levels of immune globulin (Ig) IgM and IgG, and intestinal villus height : crypt depth ratio (V/C) (P < 0.05). Meanwhile, AMPs significantly increased the challenged piglets' ADG, ADFI, G/F and V/C of the jejunum and ileum, and notably deceased the diarrhea rate (P < 0.05); (2) compared with antibiotics group, the effects of AMPs were slightly weaker than those of antibiotics in the healthy piglets, but AMPs have similar effects to those of antibiotics in challenged piglets. In a higher purity, the optimal dose of AMPs may be approximately 0.01%. Our findings indicate that AMPs can improve piglet growth performance, enhance immunity, benefit intestinal morphology and decrease the diarrheal rate. AMPs could be great ASs especially under infection conditions.

Effect of early antibiotic intervention on specific bacterial communities and immune parameters in the small intestine of growing pigs fed different protein level diets

Antibiotics are designed to affect gut microbiota and subsequently gut homeostasis. However, limited information exists about short- and long-term effects of early antibiotic intervention (EAI) on gut homeostasis (especially for the small intestine) of pigs following antibiotic withdrawal. We investigated the impact of EAI on specific bacterial communities, microbial metabolites and mucosal immune parameters in the small intestine of later-growth-stage pigs fed with diets differing in CP levels. Eighteen litters of piglets were fed creep feed with or without antibiotics from day 7 to day 42. At day 42, pigs within each group were offered a normal- or low-CP diet. Five pigs per group were slaughtered at days 77 and 120. At day 77, EAI increased Enterobacteriaceae counts in the jejunum and ileum and decreased Bifidobacterium counts in the jejunum and ileum (P < 0.05). Moreover, tryptamine, putrescine, secretory immunoglobulin (Ig) A and IgG concentrations in the ileum and interleukin-10 (IL-10) mRNA and protein levels in the jejunum and ileum were decreased in pigs with EAI (P < 0.05). At day 120, EAI only suppressed Clostridium cluster XIVa counts in the jejunum and ileum (P < 0.05). These results suggest that EAI has a short-term effect on specific bacterial communities, amino acid decarboxylation and mucosal immune parameters in the small intestine (particularly in the ileum). At days 77 and 120, feeding a low-CP diet affected Bifidobacterium, Clostridium cluster IV, Clostridium cluster XIVa and Enterobacteriaceae counts in the jejunum or ileum (P < 0.05). Moreover, feeding a low-CP diet increased the concentrations of Igs in the jejunum and decreased pro-inflammatory cytokines levels in the jejunum and ileum (P < 0.05). At day 120, feeding a low-CP diet increased short-chain fatty acid concentrations, reduced ammonia and spermidine concentrations and up-regulated genes related to barrier function in the jejunum and ileum (P < 0.05). These results suggest that feeding a low-CP diet changes specific bacterial communities and intestinal metabolite concentrations and modifies mucosal immune parameters. These findings contribute to our understanding on the duration of the impact of EAI on gut homeostasis and may provide basis data for nutritional modification in young pigs after antibiotic treatment.

Impact of Tilapia hepcidin 2-3 dietary supplementation on the gut microbiota profile and immunomodulation in the grouper (Epinephelus lanceolatus)

Hepcidin regulates iron homeostasis and host-defense mechanisms, while the hepcidin-like protein, Tilapia hepcidin (TH)2-3, functions as an antimicrobial peptide (AMP). Since AMP dietary supplements may be used as alternatives to antibiotics in livestock, we tested the effects of recombinant (r)TH2-3 as a dietary supplement in grouper aquaculture. rTH2-3 was produced by a Pichia pastoris expression system and exhibited thermostability and broad-spectrum antimicrobial activity. The feed conversion ratio and feed efficiency were determined in Epinephelus lanceolatus (grouper) fed with rTH2-3-supplemented diet for 28 days. In addition, grouper showed enhanced superoxide dismutase (SOD) activity after rTH2-3 feeding compared to regular-diet-fed fish. Gut microbiota analysis revealed that microbial diversity was enhanced by feeding grouper with 1% rTH2-3. After challenging grouper with Vibrio alginolyticus, differential regulation of immune-related genes in the liver and spleen was observed between the TH2-3 and regular-diet groups, including for genes associated with antimicrobial and pro-inflammatory functions, complement components, and major histocompatibility complex (Mhc). These findings suggest that overall immunity was improved. Thus, our results suggest long-term supplementation with rTH2-3 may be beneficial for aquacultured grouper. The beneficial effects of the supplement are likely based on changes in the commensal microbial community as well as immunomodulation.

Dietary supplementation with polypeptides improved growth performance, antibacterial immune and intestinal microbiota structure of Litopenaeus vannamei

Antibacterial peptides (AMPs) are expected to replace some or all of the antibiotics and become a new feed additive. However, the high production cost and unclear mechanism limited the application of AMPs. In this research, the effects of a commercial polypeptide (Polypeptide S100) whose main components are AMPs on the growth, antibacterial immune and intestinal microbial of Litopenaeus vannamei were study. L. vannamei (initial weight of 0.16 ± 0.03 g) were fed for 123 days with basal diet added Polypeptide S100 at two levels each (0.5% and 1%) as experimental groups, and a basal diet as control. Dietary inclusion of Polypeptide S100 at 1% level significantly increased the weight gain (WG) and specific growth rate (SGR) of L. vannamei. The survival rates of L. vannamei in 0.5% and 1% Polypeptide S100 groups were significantly higher than the control when infected by Vibrio harveyi but not Vibrio parahaemolyticus. The activities of total superoxide dismutase (T-SOD) and lysozyme (LZM) in the two experimental groups were all significantly higher than the control. Differently, the activities of amylase (AMS) and lipase (LPS) were significantly higher in 0.5% Polypeptide S100 group but lower in 1.0% Polypeptide S100 group. Illumina MiSeq high-throughput sequencing showed that the dominant phyla in the intestine of L. vannamei were Proteobacteria, followed by Actinobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Fusobacteria and Tenericutes, and the abundance of predominant phyla Cyanobacteria were upregulated significantly in the experimental groups. At the family level, significant increase was observed in Pseudomonadaceae and Xanthomonadaceae but decrease in Vibrionaceae in the 1.0% Polypeptide S100 group. The abundance of predominant genus Photobacterium were obviously downregulated in the two experimental groups. Unlikely, the abundance of Pseudomonas and Stenotrophomonas were distinctly increased in the 1.0% Polypeptide S100 group but not significantly different from the control in 0.5% Polypeptide S100 group. All these results suggested that Polypeptide S100 could improve the growth performance, antibacterial immune and intestinal microbiota structure of L. vannamei.

The Utilization of Full-Fat Insect Meal in Rainbow Trout (Oncorhynchus mykiss) Nutrition: The Effects on Growth Performance, Intestinal Microbiota and Gastrointestinal Tract Histomorphology

A 71-day-long experiment was conducted to evaluate the inclusion of 20% Hermetia illucens (HI) meal; Tenebrio molitor (TM) meal; Gryllodes sigillatus (GS) meal; and Blatta lateralis (BL) meal in comparison to a control diet without any insect-based materials that used fish meal as the main source of protein. A total of 1950 rainbow trout juveniles (53.39 ± 3.74 g) were used. The formulated diets were isonitrogenous (45%) and isoenergetic (10 MJ kg−1). The inclusion of a full-fat insect meal did not affect the survival rate during the experimental period. The growth performance was significantly improved in the BL and TM treatments, while in the HI treatment was not affected. However, the GS treatment had a negative effect on the growth performance. The villus height decreased in the TM and GS treatment groups and increased in the BL diet group. The total number of bacteria increased in all insect meal diet groups. The results of the experiment show that B. lateralis, T. molitor and H. illucens full-fat meals can be used as a partial fish meal replacement without negative effects on survival or growth performance parameters. Moreover, full-fat insect meals may be considered as a protein source and a functional feed component that may positively affect the histomorphological structure of the fish gastrointestinal tract and stimulate the expansion of beneficial bacterial populations in the gut.

Potential dietary feed additives with antibacterial effects and their impact on performance of weaned piglets: A meta-analysis

This meta-analysis evaluated the use of potential dietary feed additives (pDFA) with antibacterial effects and their impact on the perfomance of weaned piglets. Twenty-three peer-reviewed in vivo studies, comprising 50 trials, were identified between January 2010 and January 2017. The pDFA in these studies could be grouped in 5 classes: antimicrobial peptides, chitosan, lysozyme, medium chain fatty acids/ triglycerides and plant extracts. Mixed-effect meta-analyses with type of pDFA as fixed effect were performed for the growth parameters 'average daily gain' (ADG) and 'feed conversion ratio' (FCR), which are the two most important and used economic performance parameters for farmers. For each class of pDFA, results of the meta-analysis showed significantly higher average daily gain in the group with pDFA compared to the negative control group, while no significant difference with the positive control group was observed. Furthermore, a positive effect on FCR was found, i.e. significantly less feed was needed to gain 1 kg of body weight in the group with pDFA compared to the negative control group. No significant differences with positive control groups were observed for each class of pDFA, except for plant extracts, where the FCR was also significantly reduced in the treatment group. These results suggest that pDFA could reduce the use of antimicrobials without significant negative effects on performance indicators.

Antimicrobial peptides: Promising alternatives in the post feeding antibiotic era

Antimicrobial peptides (AMPs), critical components of the innate immune system, are widely distributed throughout the animal and plant kingdoms. They can protect against a broad array of infection-causing agents, such as bacteria, fungi, parasites, viruses, and tumor cells, and also exhibit immunomodulatory activity. AMPs exert antimicrobial activities primarily through mechanisms involving membrane disruption, so they have a lower likelihood of inducing drug resistance. Extensive studies on the structure-activity relationship have revealed that net charge, hydrophobicity, and amphipathicity are the most important physicochemical and structural determinants endowing AMPs with antimicrobial potency and cell selectivity. This review summarizes the recent advances in AMPs development with respect to characteristics, structure-activity relationships, functions, antimicrobial mechanisms, expression regulation, and applications in food, medicine, and animals.

Dietary supplemented antimicrobial peptide microcin J25 improves the growth performance, apparent total tract digestibility, fecal microbiota, and intestinal barrier function of weaned pigs

Microcin J25 (MccJ25) is an antimicrobial peptide produced by a fecal strain of Escherichia coli containing 21 AA. This study was performed primarily to evaluate the effects of MccJ25 as a potential substitute for antibiotics (AB) on growth performance, nutrient digestibility, fecal microbiota, and intestinal barrier function in weaned pigs. In the present study, 180 weaned pigs (7.98 ± 0.29 kg initial BW) were randomly assigned to 1 of 5 treatments, including a basal diet (CON) and CON supplemented with AB (20 mg/kg colistin sulfate; ABD) or 0.5, 1.0, and 2.0 mg/kg MccJ25. On d 0 to 14, dietary supplementation with MccJ25 and ABD had positive effects on ADG, ADFI, diarrhea incidence, and G:F ( < 0.05). Pigs fed the 2.0 mg/kg MccJ25 diet had greater ADG ( < 0.05) and marginally greater G:F ( < 0.10) compared with pigs fed the ABD diet. Compared with the CON diet, the 2.0 mg/kg MccJ25 diet sharply improved ( < 0.05) ADG and G:F and decreased ( < 0.05) diarrhea incidence (d 15 to 28 and d 0 to 28). Apparent digestibility of nutrients in pigs fed 1.0 and 2.0 mg/kg MccJ25 was improved ( < 0.05) compared with that of pigs fed CON and ABD. The serum cytokines IL-6 and IL-1β and tumor necrosis factor-α levels in pigs fed MccJ25 were greater than in pigs fed CON ( < 0.05). Additionally, the IL-10 concentration in pigs fed MccJ25 was sharply increased ( < 0.05) compared with that of pigs fed CON. Pigs fed 1.0 and 2.0 mg/kg MccJ25 diets had remarkably decreased lactate, diamine oxidase, and endotoxin concentrations and fecal numbers ( < 0.05) and improved fecal and numbers ( < 0.05). Compared with the ABD diet, the diet containing 2.0 mg/kg MccJ25 did not increase lactate, diamine oxidase, and endotoxin (d 14) concentrations ( < 0.05) or decrease the and (d 28) numbers ( < 0.05). The diets containing 1.0 and 2.0 mg/kg MccJ25 and ABD (d 28) improved lactate concentration and short-chain fatty acid concentrations, including acetate, propionate, and butyrate, in feces ( < 0.05). Moreover, the pigs fed 2.0 mg/kg MccJ25 had greater lactate, butyrate (d 14), and propionate concentrations than the pigs fed the ABD diet ( < 0.05). In conclusion, dietary supplemented MccJ25 effectively improved performance, attenuated diarrhea and systematic inflammation, enhanced intestinal barrier function, and improved fecal microbiota composition of weaned pigs. Therefore, MccJ25 could be a potential effective alternative to AB for weaned pigs.

Antimicrobial activity of a new synthetic peptide loaded in polylactic acid or poly(lactic-co-glycolic) acid nanoparticles against Pseudomonas aeruginosa, Escherichia coli O157:H7 and methicillin resistant Staphylococcus aureus (MRSA)

Nanocarrier systems are currently being developed for peptide, protein and gene delivery to protect them in the blood circulation and in the gastrointestinal tract. Polylactic acid (PLA) and poly(lactic-co-glycolic) acid (PLGA) nanoparticles loaded with a new antimicrobial GIBIM-P5S9K peptide were obtained by the double emulsion solvent extraction/evaporation method. PLA- and PLGA-NPs were spherical with sizes between 300 and 400 nm for PLA and 200 and 300 nm for PLGA and <0.3 polydispersity index as determined by dynamic light scattering and scanning electron microscopy), having the zeta potential of >20 mV. The peptide-loading efficiency of PLA-NP and PLGA-NPs was 75% and 55%, respectively. PLA- and PLGA-NPs released around 50% of this peptide over 8 h. In 10% human sera the size of peptide loaded PLA- and PLGA-NPs increased between 25.2% and 39.3%, the PDI changed from 3.2 to 5.1 and the surface charge from -7.15 to 14.6 mV. Both peptide loaded PLA- and PLGA-NPs at 0.5 μM peptide concentration inhibited the growth of Escherichia coli O157:H7 (E. coli O157:H7), methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas. aeruginosa (P. aeruginosa). In contrast, free peptide inhibited at 10 μM but did not inhibit at 0.5 and 1 μM. These PLA- and PLGA-NPs presented <10% hemolysis indicating that they are hemocompatible and promising for delivery and protection system of GIBIM-P5S9K peptide.

Bacteriophage cocktail and multi-strain probiotics in the feed for weanling pigs: effects on intestine morphology and targeted intestinal coliforms and Clostridium

Two experiments were conducted to investigate the effects of dietary supplementation of bacteriophage cocktail, probiotics and a combination of these two supplements on performance and gut health of weanling pigs. In Experiment 1, 150 weaned piglets were randomly allotted to three treatments on the basis of BW. The dietary treatments included a basal diet supplemented with 0 (control), 1.0 and 1.5 g/kg bacteriophage cocktail. Pigs fed 1.0 and 1.5 g/kg bacteriophage product had greater (P<0.05) average daily gain (ADG), apparent total tract digestibility of dry matter from day 22 to 35, ileal Lactobacillus spp., villus height (duodenum and jejunum), and fewer coliforms (ileum) and Clostridium spp. (ileum). In Experiment 2, 200 weaned piglets were randomly allotted to four treatments. Dietary treatments included basal diet, basal diet supplemented with 3.0 g/kg fermented probiotic product (P), 1.0 g/kg bacteriophage cocktail (B) and combination of 1.0 g/kg bacteriophage cocktail and 3.0 g/kg fermented probiotic product. Pigs fed bacteriophage cocktail diets had greater (P<0.05) overall ADG, gain to feed ratio (G : F), fecal score from day 8 to day 21, and pigs fed bacteriophage cocktail diets had fewer coliforms (ileum) Clostridium spp. (ileum and cecum). Probiotics significantly increased G : F, colonization of Lactobacillus spp. in ileum. At day 35, bacteriophage treatment group showed greater (P<0.05) villus height of the duodenum, but a deeper crypt in duodenum. The present results indicate that the bacteriophage cocktail had a potential to enhance the performance and gut health of weanling pigs, however their combination with probiotics did not show an interaction.

High therapeutic efficacy of Cathelicidin-WA against postweaning diarrhea via inhibiting inflammation and enhancing epithelial barrier in the intestine

Diarrhea is a leading cause of death among young mammals, especially during weaning. Here, we investigated the effects of Cathelicidin-WA (CWA) on diarrhea, intestinal morphology, inflammatory responses, epithelial barrier and microbiota in the intestine of young mammals during weaning. Piglets with clinical diarrhea were selected and treated with saline (control), CWA or enrofloxacin (Enro) for 4 days. Both CWA and Enro effectively attenuated diarrhea. Compared with the control, CWA decreased IL-6, IL-8 and IL-22 levels and reduced neutrophil infiltration into the jejunum. CWA inhibited inflammation by down-regulating the TLR4-, MyD88- and NF-κB-dependent pathways. Additionally, CWA improved intestinal morphology by increasing villus and microvillus heights and enhancing intestinal barrier function by increasing tight junction (TJ) protein expression and augmenting wound-healing ability in intestinal epithelial cells. CWA also improved microbiota composition and increased short-chain fatty acid (SCFA) levels in feces. By contrast, Enro not only disrupted the intestinal barrier but also negatively affected microbiota composition and SCFA levels in the intestine. In conclusion, CWA effectively attenuated inflammation, enhanced intestinal barrier function, and improved microbiota composition in the intestines of weaned piglets. These results suggest that CWA could be an effective and safe therapy for diarrhea or other intestinal diseases in young mammals.

Regulation of the Intestinal Barrier Function by Host Defense Peptides

Intestinal barrier function is achieved primarily through regulating the synthesis of mucins and tight junction (TJ) proteins, which are critical for maintaining optimal gut health and animal performance. An aberrant expression of TJ proteins results in increased paracellular permeability, leading to intestinal and systemic disorders. As an essential component of innate immunity, host defense peptides (HDPs) play a critical role in mucosal defense. Besides broad-spectrum antimicrobial activities, HDPs promotes inflammation resolution, endotoxin neutralization, wound healing, and the development of adaptive immune response. Accumulating evidence has also indicated an emerging role of HDPs in barrier function and intestinal homeostasis. HDP deficiency in the intestinal tract is associated with barrier dysfunction and dysbiosis. Several HDPs were recently shown to enhance mucosal barrier function by directly inducing the expression of multiple mucins and TJ proteins. Consistently, dietary supplementation of HDPs often leads to an improvement in intestinal morphology, production performance, and feed efficiency in livestock animals. This review summarizes current advances on the regulation of epithelial integrity and homeostasis by HDPs. Major signaling pathways mediating HDP-induced mucin and TJ protein synthesis are also discussed. As an alternative strategy to antibiotics, supplementation of exogenous HDPs or modulation of endogenous HDP synthesis may have potential to improve intestinal barrier function and animal health and productivity.

The application of antimicrobial peptides as growth and health promoters for swine

With the widespread ban on the use of antibiotics in swine feed, alternative measures need to be sought to maintain swine health and performance. Antimicrobial peptides (AMPs) are part of the nonspecific defense system and are natural antibiotics produced by plants, insects, mammalians, and micro-organisms as well as by chemical synthesis. Due to their broad microbicidal activity against various fungi, bacteria and enveloped viruses, AMPs are a potential alternative to conventional antibiotics for use in swine production. This review focuses on the structure and mechanism of action of AMPs, as well as their effects on performance, immune function and intestinal health in pigs. The aim is to provide support for the application of AMPs as feed additives replacing antibiotics in swine nutrition.