Effects of dietary addition of heat-killed Mycobacterium phlei on growth performance, immune status and anti-oxidative capacity in early weaned piglets

Research progress into the application of Mycobacterium phlei in veterinary medicine

Mycobacterium phlei is a gram-positive acid-fast mycobacterium from the family Mycobacteriaceae. It is a valuable resource for both natural drugs and microecological preparations. It has been widely used in the field of human medicine; however, in the field of animal husbandry and veterinary medicine, the research and application of M. phlei is still in the preliminary exploration stage. This study aims to summarize the research progress of M. phlei in the field of veterinary medicine and provide a valuable reference for future research. Key words, such as 'M. phlei', 'veterinary field', 'immune balancer', 'genome' and other relevant words to this study, were used to search through PubMed, Web of Science, SciELO, Science Direct and Google Scholar databases. The results showed that the culture conditions of M. phlei were relatively simple, but its bacterial composition and genome sequence were relatively complex, and various components in the cell wall may have immunoregulatory effects. Therefore, the inactivated preparation made from M. phlei can have various applications in the veterinary field, such as growth regulation, immune regulation, antitumour, anti-parasite and asthma treatment. The literature review indicates that M. phlei preparation is an efficient and convenient immune system balance agent. Despite the challenges associated with the use of M. phlei preparations, it has a strong potential for application in veterinary medicine.

Changes in intestinal morphology, number of mucus-producing cells and expression of coronavirus receptors APN, DPP4, ACE2 and TMPRSS2 in pigs with aging

Porcine enteric viral infections cause high morbidity and mortality in young piglets (<3 weeks). Later, these rates decrease with age. This age-dependent infectivity remains largely unexplored. This study investigated the changes in intestinal morphology, number of mucus-producing cells and expression level of coronavirus receptors in three age groups of pigs. Villus height and crypt depth increased with age from 3 days to 3 months in duodenum and ileum but not in mid-jejunum, where the villus height decreased from 580 µm at 3 days to 430 µm at 3 months. Enterocyte length-to-width ratio increased from 3 days to 3 months in all intestinal regions. The number of mucus-producing cells increased with age in the intestinal villi and crypts. The Brunner's glands of the duodenum contained the highest concentration of mucus-producing cells. The expression of coronavirus receptor APN was highest in the small intestinal villi at all ages. DPP4 expression slightly decreased over time in jejunum and ileum; it was highest in the ileal villi of 3-day-old piglets (70.2% of cells). ACE2 and TMPRSS2 positive cells increased with age in jejunal and ileal crypts and were particularly dominant in the ileal crypts (> 45% of cells). Except for the expression of DPP4 in the jejunum and ileum of young pigs, the expression pattern of the selected coronavirus receptors was very different and not correlated with the age-dependent susceptibility to viral infections. In contrast, the number of mucus-producing cells increased over time and may play an essential role in protecting enteric mucosae against intestinal viruses.

Potential of Oral Nanoparticles Containing Cytokines as Intestinal Mucosal Immunostimulants in Pigs: A Pilot Study

Simple Summary

Antibiotics are essential compounds to cope with bacterial infections. However, their inadequate and excessive use has triggered the rapid arising of antimicrobial-resistant bacteria. In this scenario, immunostimulants, which are molecules that boost the immune system, open up a new approach to face this problem, enhancing treatment efficacy and preventing infections by immune system response. Cytokines are central effector molecules of the immune system, and their recombinant production and administration in animals could be an interesting immune modulation strategy. The aim of this study was the development of a highly stable nanoparticle of porcine cytokines to achieve the immunostimulation of intestinal mucosa in piglets. The outcomes of the present study prove this approach is able to stimulate swine intestinal cells and macrophages in vitro and tends to modulate inflammatory responses in vivo, although further studies are required to definitively evaluate their potential in animals.

Abstract

Antimicrobial resistance is a global threat that is worryingly rising in the livestock sector. Among the proposed strategies, immunostimulant development appears an interesting approach to increase animal resilience at critical production points. The use of nanoparticles based on cytokine aggregates, called inclusion bodies (IBs), has been demonstrated as a new source of immunostimulants in aquaculture. Aiming to go a step further, the objective of this study was to produce cytokine nanoparticles using a food-grade microorganism and to test their applicability to stimulate intestinal mucosa in swine. Four cytokines (IL-1β, IL-6, IL-8, and TNF-α) involved in inflammatory response were produced recombinantly in Lactococcus lactis in the form of protein nanoparticles (IBs). They were able to stimulate inflammatory responses in a porcine enterocyte cell line (IPEC-J2) and alveolar macrophages, maintaining high stability at low pH and high temperature. In addition, an in vivo assay was conducted involving 20 piglets housed individually as a preliminary exploration of the potential effects of IL-1β nanoparticles in piglet intestinal mucosa after a 7 d oral administration. The treated animals tended to have greater levels of TNF-α in the blood, indicating that the tested dose of nanoparticles tended to generate an inflammatory response in the animals. Whether this response is sufficient to increase animal resilience needs further evaluation.

Synergistic activity and immunomodulatory potential of levofloxacin and Synoeca-MP peptide against multi-resistant strains of Klebsiella pneumoniae

The purpose of this article is to study the isolated and combined effect of the peptides Synoeca-MP and IDR-1018 against multi-resistant clinical isolates of K. pneumoniae (Kp2177569 - LACEN) in vitro. The bactericidal activity of the peptide Synoeca-MP in combination with three different classes of commercial antimicrobials and its immunomodulatory potential was also evaluated. Synoeca-MP showed better antimicrobial activity than IDR-1018 and presented synergistic action combined with levofloxacin. Therefore, Synoeca-MP and levofloxacin, and the combination of both, were used in subsequent analyses. In the presence of heat-killed antigens, cellular viability and TNF-α levels was maintained, the production of NO increased and a reduction in IL-10 production was observed. The synergistic antibacterial effect between Synoeca-MP and levofloxacin was effective against multidrug-resistant strains of K. pneumoniae. The association of Synoeca-MP and levofloxacin may present a low modulating action of pro and anti-inflammatory mediators, based on these results.

Dietary Probiotics or Synbiotics Supplementation During Gestation, Lactation, and Nursery Periods Modifies Colonic Microbiota, Antioxidant Capacity, and Immune Function in Weaned Piglets

This study was conducted to investigate the effect of dietary probiotics or synbiotics supplementation on colonic microbiota, antioxidant capacity, and immune function in weaned piglets. A total of 64 pregnant Bama mini-sows and then 128 of their weaned piglets were randomly assigned into control group, antibiotics group, probiotics group, or synbiotics group. The results showed that colonic Firmicutes and Bifidobacterium abundances in the probiotics group and total bacteria, Bacteroidetes, and Lactobacillus abundances in the synbiotics group were increased (P < 0.05), while Escherichia coli abundance in the synbiotics group was decreased (P = 0.061) compared with the control group. Firmicutes, Bifidobacterium, and total bacteria abundances were increased (P < 0.05) in the probiotics and synbiotics groups compared with the antibiotics group. Probiotics supplementation up-regulated (P < 0.05) the mRNA expression of GPR109A compared with the control and antibiotics groups. Dietary probiotics or synbiotics supplementation improved the antioxidant capacity by increasing (P < 0.05) the colonic CAT, GSH-Px, SOD, and T-AOC levels and plasma CAT, GSH, GSH-Px, and SOD levels and by decreasing (P < 0.05) the colonic and plasma MDA and H₂O₂ levels. Compared to the control group, the colonic IL-10, IFN-α, and sIgA concentrations and plasma IgA and IgM concentrations were significantly increased (P < 0.05) in the probiotics and synbiotics groups. Spearman's correlation analysis showed that the changed colonic microbiota, such as Lactobacillus and Bifidobacterium were correlated with the alteration of antioxidant indexes, cytokines, and immunoglobulins. In conclusion, dietary probiotics or synbiotics supplementation during gestation, lactation, and nursery periods could be used as an alternative for antibiotics in terms of gut health of weaned piglets.

Rapid Communication: The relationship of enterocyte proliferation with intestinal morphology and nutrient digestibility in weaning piglets

Understanding the regulatory mechanisms of intestinal morphology and function is essential for improving postweaning growth in pigs. The objective of this study was to identify the relationships of enterocyte proliferation with intestinal villus height, crypt depth, and nutrient digestibility in piglets. Sixty-four 21-d-old weaned piglets were used. Gastrointestinal cell proliferation was evaluated via Ki-67 immunohistochemistry. Villus height and crypt depth were measured using hematoxylin and eosin (H&E)-stained sections. The apparent total tract digestibility (ATTD) of CP and GE was determined by chemical analysis. The activities of lactase and sucrase were determined with commercial kits. Western blot was carried out to assess the expression of nutrient transporters. The number of Ki-67 positive cells was associated with villus height (r = 0.548, P < 0.001) and crypt depth (r = 0.759, P < 0.001) in the jejunum. The number of Ki-67 positive cells was also associated with the ATTD of CP (r = 0.715, P = 0.001). Furthermore, a positive relationship between Ki-67 positive cell populations and lactase activity (r = 0.559, P < 0.001) was observed. Additionally, the number of Ki-67 positive cells was associated with the protein expression levels of nutrient transporters PEPT1 (r = 0.511, P = 0.030) and SGLT1 (r = 0.601, P = 0.014). Weak relationships were found between Ki-67 positive cell numbers and the ATTD of GE (r = 0.401, P = 0.099) and the activity of sucrase (r = 0.313, P = 0.087). In conclusion, enterocyte proliferation was positively associated with intestinal villus height, crypt depth, and nutrient digestibility in weaning piglets. Our findings suggested that intestinal morphology and function can be improved by regulating epithelial cell proliferation in piglets.

Effects of dietary supplementation with epidermal growth factor on nutrient digestibility, intestinal development and expression of nutrient transporters in early-weaned piglets

The abnormalities in intestinal morphology and digestive function during weaning are associated with the loss of milk-borne growth factors. Epidermal growth factor (EGF) has been shown to stimulate the growth of animals. This study was to determine the effect of dietary EGF on nutrient digestibility, intestinal development and the expression of genes encoding nutrient transporters in weaned piglets. Forty-two piglets were weaned at 21 days and assigned to one of three treatment groups: (1) basal diet (control), (2) basal diet + 200 µg/kg EGF or (3) basal diet + 400 µg/kg EGF. Each treatment consisted of 14 replicates, and seven piglets from each treatment were sampled on day 7 and 14. The EGF supplementation significantly elevated (p < 0.05) the coefficients of total tract apparent digestibility of crude protein, calcium and phosphorus, but tended to decrease sucrase activity (p < 0.10) than the control group. At day 7 post-weaning, animals receiving EGF diets showed a tendency (p < 0.10) towards greater ileal villus height (VH), jejunal crypt depth (CD) and duodenal VH:CD when compared with the control group. Moreover, the mRNA levels of glucose transporter 2 (Slc2a2), neutral amino acid transporter (Slc6a19) and calbindin D9k (S100G) tended to be higher (p < 0.10) for EGF groups than the control group. By day 14, EGF supplementation markedly enhanced (p < 0.05) the VH, CD and VH:CD in the jejunum compared to the control group. This addition also up-regulated (p < 0.05) the mRNA level and the protein abundance of peptide transporter 1 than the control group. These findings demonstrated that dietary EGF beneficially enhanced nutrient digestibility, improved intestinal development and increased the mRNA expression of nutrient transporters in weaned piglets.

Effects of an immune stimulant, inactivated Mycobacterium phlei, on the growth performance as well as meat quality of fattening pigs

Inactivated mycobacterium phlei (M. phlei) is well known for its immune-stimulatory functions in humans and livestock, but less information is available about the influence on meat quality of pigs when used as a feed additive. This study was designed to evaluate the effects of inactivated M. phlei on growth performance as well as meat quality of fattening pigs. A total of 240 cross-bred pigs ([Landrace × Yorkshire] × Duroc) with initial body weight of 80.14 ± 0.29 kg were randomly allocated to five treatments, each of which consisted of eight replicates with 6six pigs per replicate. The basal diet supplemented with five levels of inactivated M. phlei preparations (0, 3.5 × 10⁹ [0.1% w/w], 7 × 10⁹ [0.2%], 1.4 × 10¹⁰ [0.4%] or 2.1 × 10¹⁰ [0.6%] colony-forming units/kg) was respectively fed to the control group and four treatment groups for 30 days. Adding 0.4% of inactivated M. phlei to diet increased the average daily feed intake and average daily gain of pigs. Importantly, intramuscular fat percentage in the Longissimus dorsi (LD) was increased by feeding diet containing 0.2%, 0.4% and 0.6% of inactivated M. phlei, despite the pH value, drip loss, cooking loss and filter paper fluid uptake not being influenced. Analysis of the fatty acid components showed that some saturated fatty acids were decreased in LD after feeding inactivated M. phlei, but some monounsaturated fat acids (MUFAs) and polyunsaturated fatty acids were increased (PUFAs), which induced the total contents of MUFAs and PUFAs were improved. RT-PCR assay revealed that feeding inactivated M. phlei up-regulated genes implicated in fat metabolism in muscle, including ELOVL6, FASN, SCD1 and H-FABP. This study revealed that feeding inactivated M. phlei not only increased growth performance of fattening pigs, but also improved the meat quality by increasing intramuscular fat content, thus inactivated M. phlei probably has high utilization value in modern pig production.