Mutual interaction between gut microbiota and protein/amino acid metabolism for host mucosal immunity and health

In recent years, many studies have shown that the intestinal microflora has various effects that are linked to the critical physiological functions and pathological systems of the host. The intestinal microbial community is widely involved in the metabolism of food components such as protein, which is one of the essential nutrients in diets. Additionally, dietary protein/amino acids have been shown to have had a profound impact on profile and operation of gut microbiota. This review summarizes the current literature on the mutual interaction between intestinal microbiota and protein/amino acid metabolism for host mucosal immunity and health.     

Characterisation of chloride currents in the jejunum and colon of pigs

Chloride secretion in the intestines of pigs of different age (32 days and 4 months) was examined using the Ussing chamber technique. After stimulating chloride secretion by carbachol and forskolin, alternative chloride channels and finally Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) channels were blocked. While basal short-circuit currents (I_sc) were higher in the jejunum than in the colon of the piglets of 32 days, it was inverse for the 4-month-old fatteners. In the jejunum responses to stimulation and final levels of I_sc were higher in the piglets than in the fatteners. The decrease in I_sc after blocking CFTR channels was smaller in the fatteners than in the piglets in both intestinal segments. In conclusion, 32-day-old piglets show a higher basal chloride secretion as well as a higher response to stimulation in the jejunum than 4-month-old pigs.     

Porcine reproductive and respiratory syndrome virus induces pronounced immune modulatory responses at mucosal tissues in the parental vaccine strain VR2332 infected pigs

Porcine reproductive and respiratory syndrome (PRRS) is a chronic viral disease of pigs caused by PRRS virus (PRRSV). The PRRSV VR2332 is the prototype North American parental strain commonly used in the preparation of vaccines. Goal of this study was to understand missing information on VR2332 induced immune modulation at the lungs and lymphoid tissues, the sites of PRRSV replication. Pigs were infected intranasally and samples collected at post-infection day (PID) 15, 30, and 60. Microscopically, lungs had moderate interstitial pneumonia, and the virus was detected in all the tested tissues. Peak antibody response and the cytokine IFN-γ secretion were detected at PID 30, with increased TGF-β until PID 60. Population of CD8⁺, CD4⁺, and CD4⁺CD8⁺T cells, Natural killer (NK) cells, and γδ T cells in the lungs and lymphoid tissues were significantly modulated favoring PRRSV persistence. The NK cell-mediated cytotoxicity was significantly reduced in infected pigs. In addition, increased population of immunosuppressive T-regulatory cells (Tregs) and associated cytokines were also observed in VR2332 strain infected pigs.     

地塞米松对仔猪十二指肠黏膜免疫的影响

为了探讨地塞米松对仔猪肠道黏膜的影响,选用福州周边某猪场30日龄仔猪30头,随机分为6组,3组为试验组,3组为对照组,试验Ⅰ、Ⅱ、Ⅲ组分别肌肉注射1 mL、2 mL、3 m L地塞米松,对照组Ⅰ、Ⅱ、Ⅲ组分别肌肉注射1 mL、2 m L、3 mL生理盐水;药物试验7 d后,取十二指肠固定、脱水、包埋、切片,经HE染色、阿利新蓝-过碘雪夫(AB-PAS)染色,检测地塞米松对肠道绒毛高度、隐窝深度、绒毛高度和隐窝深度比值、黏液细胞、上皮内淋巴细胞数量的影响。结果表明:长时间过量注射地塞米松抑制肠绒毛生长,显著降低肠绒毛长度和隐窝深度比值,显著性降低仔猪十二指肠上皮酸性黏多糖阳性细胞和上皮内淋巴细胞数量。可见,持续过量注射地塞米松将影响十二指肠黏膜免疫功能。     

Effect of the route of administration on the mucosal and systemic immune responses to Lawsonia intracellularis vaccine in pigs

In an on‐farm study, 40 weaned piglets aged 3 weeks were vaccinated with Lawsonia intracellularis vaccine orally, IM or IP while a fourth group remained unvaccinated. All vaccinated animals showed increased serum levels of L. intracellularis‐specific IgG antibodies, but significantly elevated concentrations of specific IgG, IgA and cytokines were generated in ileal mucosal secretions from the orally and IP vaccinated pigs when examined at 17 days after vaccination.     

疫尅灵与新城疫活疫苗（LaSota株）诱导雏鸡黏膜免疫的对比试验

新城疫病毒是副黏病毒,对鸡的黏膜有特殊的亲嗜性,极易经呼吸道和消化道感染,利用弱毒疫苗的局部免疫作用封锁新城疫强毒的入侵门户,是防制新城疫的重要措施。本试验利用疫尅灵与新城疫活疫苗（LaSota株）分别免疫SPF鸡雏,于免疫后不同时间检测免疫鸡雏泪液中的IgA,发现疫尅灵免疫组均高于LaSota株免疫组和对照组,说明疫尅灵在新城疫免疫上具高的诱导黏膜免疫能力。     

Fatty acids,inflammation and intestinal health in pigs

The intestine is not only critical for nutrient digestion and absorption, but also is the largest immune organ in the body. However, in pig production, inflammation induced by numerous factors, such as pathogen infection and stresses (e.g., weaning), results in intestinal mucosal injury and dysfunction, and consequently results in poor growth of pigs. Dietary fatty acids not only play critical roles in energy homeostasis and cellular membrane composition, but also exert potent effects on intestinal development, immune function, and inflammatory response. Recent studies support potential therapeutic roles for specific fatty acids (short chain and medium chain fatty acids and long chain polyunsaturated fatty acids) in intestinal inflammation of pigs. Results of these new lines of work indicate trophic and cytoprotective effects of fatty acids on intestinal integrity in pigs. In this article, we review the effect of inflammation on intestinal structure and function, and the role of specific fatty acids on intestinal health of pigs, especially under inflammatory conditions.     

Gut growth and glucose tolerance in newborn pigs subjected to prenatal protein restriction and postnatal Glucagon-like Peptides

Fetal protein restriction is potentially associated with organ dysfunctions after birth (e.g. impaired gut growth, glucose tolerance and pancreatic β-cell function). Just after birth, gut growth and maturation is stimulated by enteral food intake, and inhibited by total parenteral nutrition (TPN), in part mediated via differential release of insulino- and intestino-tropic hormones like the Glucagon-Like Peptides 1 and 2 (GLP-1, GLP-2). We hypothesized that short-term co-infusion of GLP-1 and GLP-2 would stimulate pancreatic and intestinal growth in newborn TPN-fed pigs subjected to prenatal protein restriction. Two sows were fed a protein-restricted diet (PR: 8% crude protein during last 50% of gestation) while a third sow was fed a control diet (C: 15% crude protein). PR pigs were killed either at birth (n = 7) or after 3 days TPN with (n = 6) or without (n = 4) intravenous infusion of a mixture of synthetic human GLP-1_7–37 and GLP-2_1–33 (each 50 μg/kg/d). At birth, PR piglets did not show reduced body weight, relative to controls (1.45 vs. 1.50 kg), but significantly reduced weight of the small intestine (18.0 ± 0.6 vs. 21.9 ± 0.5 g/kg, P < 0.001) and a marginally reduced pancreas weight (0.85 ± 0.02 vs. 0.93 ± 0.04 g/kg, P = 0.10). Co-infusion GLP-1 and GLP-2 into PR pigs resulted in increased basal glucose levels (5.3 vs. 4.0 mM), and glucose-stimulated insulin release, but did not have any significant effect on body weight, or weight of internal organs (heart, lungs, spleen, kidneys, adrenals, stomach, colon, liver, intestine, pancreas). We conclude that short-term (3 days) infusion of native GLP-1 and GLP-2 does not stimulate gut growth or glucose tolerance in TPN-fed piglets born from protein-restricted mothers. Moderate maternal protein restriction does however cause significant reduction in intestinal growth in newborn piglets which may decrease the neonatal digestive capacity.     

Fiber effects in nutrition and gut health in pigs

Dietary fiber is associated with impaired nutrient utilization and reduced net energy values. However, fiber has to be included in the diet to maintain normal physiological functions in the digestive tract. Moreover, the negative impact of dietary fiber will be determined by the fiber properties and may differ considerably between fiber sources. Various techniques can be applied to enhance nutritional value and utilization of available feed resources. In addition, the extent of fiber utilization is affected by the age of the pig and the pig breed. The use of potential prebiotic effects of dietary fiber is an attractive way to stimulate gut health and thereby minimize the use of anti-microbial growth promoters. Inclusion of soluble non-starch polysaccharides （NSP） in the diet can stimulate the growth of commensal gut microbes, inclusion of NSP from chicory results in changes in gut micro-environment and gut morphology of pigs, while growth performance remains unaffected and digestibility was only marginally reduced. The fermentation products and pH in digesta responded to diet type and were correlated with shifts in the microbiota. Interestingly, fiber intake will have an impact on the expression of intestinal epithelial heat-shock proteins in the pig. Heat-shock proteins have an important physiological role in the gut and carry out crucial housekeeping functions in order to maintain the mucosal barrier integrity. Thus, there are increasing evidence showing that fiber can have prebiotic effects in pigs due to interactions with the gut micro-environment and the gut associated immune system.     

Regulating effects and mechanisms of Chinese medicine decoction on growth and gut hormone expression in heat stressed pigs

Exposure to high temperatures during the summer renders pigs susceptible to severe heat stress. Our previous studies found that pig small intestine epithelial tissue became significantly damaged following exposure to heat stress, negatively affecting body weight gain. The deleterious effects of heat stress could be ameliorated using a traditional Chinese medicine decoction (CMD), sustaining normal growth while under heat stress. In the current study, we hypothesized the mechanism of CMD activity to be via regulation of gut hormones (NPY, MLN, SCT and GCG) secretion from endocrine cells, which are responsible for nutrient digestion and absorption. To test this, 36 Chinese experimental mini-pigs (2 months of age) were screened according to weight and litter origin, and divided into three treatment groups: control (23 °C for 24 h + standard feed), heat stress (HS; 26 °C for 19 h, 40 °C for 5 h + standard feed) and CMD (26 °C for 19 h, 40 °C for 5 h + standard feed supplemented with CMD); n = 12 per group. Feed intake and body weight gain were measured daily. Pigs were euthanized at days 1 and 6 after initial treatment with blood and sections of small intestine epithelial tissue collected. Serum cortisol (Cor) concentrations were determined using RIA. Endocrine cell number and structural analysis were performed using silver staining, and gut hormone secretion examined by microarray. Dietary supplementation with CMD significantly improved porcine growth performance (P < 0.05), decreased the Cor levels (P < 0.01), increased endocrine cell number as well as up-regulating neuropeptide Y (NPY), motilin (MLN) and secretin (SCT) and down-regulating glucagon (GCG) expression in pig jejunum on day 6 when compared with the HS group. Taken together, our results indicate CMD supplementation can significantly reduce the negative effects of heat stress on pig jejunum, maintaining growth performance similar to non-heat stressed animals. CMD's activity appears to be via adjusting gut hormone secretion to regulate metabolism and improve animal growth.     

Systemic and local immune response in pigs intradermally and intramuscularly injected with inactivated Mycoplasma hyopneumoniae vaccines

The systemic and respiratory local immune response induced by the intradermal administration of a commercial inactivated Mycoplasma hyopneumoniae whole-cell vaccine (Porcilis^® MHYO ID ONCE – MSD AH) in comparison with two commercial vaccines administered via the intramuscular route and a negative control (adjuvant only) was investigated. Forty conventional M. hyopneumoniae-free pigs were randomly assigned to four groups (ten animals each): Group A = intradermal administration of the test vaccine by using the needle-less IDAL^® vaccinator at a dose of 0.2 ml; Group B = intramuscular administration of a commercially available vaccine (vaccine B); Group C = intramuscular administration of the adjuvant only (2 ml of X-solve adjuvant); Group D = intramuscular administration of a commercially available vaccine (vaccine D). Pigs were vaccinated at 28 days of age. Blood and bronchoalveolar lavage (BAL) fluid samples were collected at vaccination (blood only), 4 and 8 weeks post-vaccination. Serum and BAL fluid were tested for the presence of antibodies by ELISA test. Peripheral blood monomorphonuclear cells (PBMC) were isolated to quantify the number of IFN-γ secreting cells by ELISpot. Moreover, cytokine gene expression from the BAL fluid was performed. Total antibodies against M. hyopneumoniae and specific IgG were detected in serum of intradermally and intramuscularly (vaccine B only) vaccinated pigs at 4 and 8 weeks post-vaccination. M. hyopneumoniae specific IgA were detected in BAL fluid from vaccinated animals (Groups A and B) but not from controls and animals vaccinated with the bacterin D (p < 0.05). Significantly higher gene expression of IL-10 was observed in the BAL fluid at week 8 post-vaccination in the intradermally vaccinated pigs (p < 0.05). The results support that the intradermal administration of an adjuvanted bacterin induces both systemic and mucosal immune responses. Moreover, the intramuscularly administered commercial vaccines each had a different ability to stimulate the immune response both systemically and locally.     

The development and role of microbialhost interactions in gut mucosal immune development

At birth the piglet's immune system is immature and it is dependent upon passive maternal protection until weaning.The piglet's mucosal immune system develops over the first few weeks but has not reached maturity at weaning ages which are common on commercial farms. At weaning piglets are presented with a vast and diverse range of microbial and dietary/environmental antigens. Their ability to distinguish between antigens and mount a protective response to potential pathogens and to develop tolerance to dietary antigens is critical to their survival and failure to do so is reflected in the high incidence of morbidity and mortality in the post-weaning period. A growing recognition that the widespread use of antibiotics to control infection during this critical period should be controlled has led to detailed studies of those factors which drive the development of the mucosal immune system, the role of gut microbiota in driving this process, the origin of the bacteria that colonise the young piglet's intestine and the impact of rearing environment. This review briefly describes how the mucosal immune system is equipped to respond appropriately to antigenic challenge and the programmed sequence by which it develops. The results of studies on the critical interplay between the host immune system and gut microbiota are discussed along with the effects of rearing environment. By comparing these with results from human studies on the development of allergies in children, an approach to promote an earlier maturation of the piglet immune system to resist the challenges of weaning are outlined.     

Active immunity and T-cell populations in pigs intraperitoneally inoculated with baculovirus-expressed transmissible gastroenteritis virus structural proteins

The intraperitoneal inoculation of pigs with baculovirus-expressed transmissible gastroenteritis virus (TGEV) structural proteins (S, N, M) in conjunction with thermolabile Escherichia coli mutant toxin (LT-R192G) in incomplete Freund’s adjuvant (IFA) was tested in an attempt to elicit active immunity to TGEV in gut-associated lymphoid tissues (GALT). Four groups of 63 (1–5-week-old) suckling, TGEV-seronegative pigs were used to assess the efficacy of the recombinant protein vaccine (group 3) in comparison with sham (group 1), commercial vaccine (group 2), and virulent TGEV Miller-strain-inoculated pigs (group 4). The TGEV-specific mucosal and systemic immune responses were measured after in vivo and in vitro stimulation with TGEV-antigens. The major T-cell subset distribution was analyzed in vivo and in vitro after stimulation of mononuclear cells with TGEV (from mesenteric lymph nodes of group 3 inoculated with TGEV-recombinant proteins). Induction of active immunity was assessed by challenge of pigs with virulent TGEV at 27 days of age. Baculovirus-expressed TGEV proteins coadministered with LT-R192G in IFA induced mesenteric lymph node immune responses associated with IgA-antibodies to TGEV and partial protection against TGEV-challenge. The high titers of serum IgG- and virus-neutralizing-antibodies to TGEV in group 3 pigs most likely reflected the dose of TGEV S-protein administered. At the day of TGEV-challenge, the in vitro stimulation of mononuclear cells from the mesenteric lymph nodes of group 3 pigs with inactivated TGEV resulted in an increase in double positive (CD4+CD8+), natural killer (CD2+CD4−CD8+dim) and cytotoxic (CD2+CD4−CD8+bright) T-cell phenotypes, accompanied by increased expression of interleukin-2 receptor and a decrease of the null (CD2−CD4−CD8−/SW6+) cell phenotype.     

Infrared skin temperature measurements for monitoring health in pigs: a review

Infrared temperature measurement equipment (IRTME) is gaining popularity as a diagnostic tool for evaluating human and animal health. It has the prospect of reducing subject stress and disease spread by being implemented as an automatic surveillance system and by a quick assessment of skin temperatures without need for restraint or contact. This review evaluates studies and applications where IRTME has been used on pigs. These include investigations of relationships between skin, ambient and body temperatures and applications for detecting fever, inflammation, lesions, ovulation, and stress as well as for meat quality assessment. The best skin locations for high correlation between skin temperature and rectal temperature are most likely thermal windows such as ear base, eye region and udder. However, this may change with age, stressors, and biological state changes, for example, farrowing. The studies performed on pigs using IRTME have presented somewhat discrepant results, which could be caused by inadequate equipment, varying knowledge about reliable equipment operation, and site-specific factors not included in the assessment. Future focus areas in the field of IRTME are suggested for further development of new application areas and increased diagnostic value in the porcine and animal setting in general.     

日粮纤维与猪肠道健康的相关性研究与应用

在生猪产能恢复中,需要特别关注猪只肠道健康问题.很多营养素与猪的肠道健康密切相关,其中日粮纤维就是影响猪只肠道健康的重要营养素之一.日粮纤维在调节猪肠道微生态环境方面表现出异常活跃的营养学功能.日粮中适宜的纤维水平可改善猪肠道微生物种群多样性,调节菌群结构组成,维持猪肠道微生态平衡,提高饲料转化率,具有促进猪只的生长发...     

甘露寡糖对保育猪的营养与保健作用

大量研究表明,甘露寡糖(MOS)通过积极影响断奶仔猪的肠道微生物菌群和肠道形态结构,加速由于断奶饥饿应激或采食固体饲料中抗原受损伤的肠黏膜上皮的修复,有助于保持仔猪断奶后肠道的完整性和消化吸收功能。在免疫反应方面,MOS通过促进抗原提呈增强断奶仔猪的抗病性,从而增强从先天性免疫应答向适应性免疫应答的转变。     

日粮膳食纤维与猪肠道健康调控

日粮纤维目前基本认定为第七大营养素,在猪体内中虽然消化率不高,甚至会影响其他营养素消化吸收,但能发酵产生短链脂肪酸,具有改善肠道微生物环境、调控母猪生理行为、调控猪肠道健康等作用。文章综述了日粮纤维在猪体内的营养特性和对肠道的调控作用,为日粮纤维在猪生产中的应用提供参考。     

Role of yeast cell wall polysaccharides in pig nutrition and health protection

Polysaccharides are the major components of the yeast cell wall and play multiple functions, ranging from the carriers of immunochemical specificity and marker molecules, by which cells recognize each other and interact with the environment, to the skeletal substances that define stability, shape, and morphology of the cell. In Saccharomyces cerevisiae, the two major polysaccharides, constituting up to 90% of the cell wall dry weight, are -d-mannan and β-d-glucan, which have remarkable properties to interact with the immune system of the host. Modulation of mucosal immunity by the binding of these two polysaccharides to the specific receptors of immune cells provides beneficial effects on animal health and resistance to diseases. Specific commercial yeast cell wall polysaccharides supplied in feed (Bio-Mos®, Alltech Inc.) are able to block fimbriae of pathogenic bacteria, and thus prevent their adhesion to the mucous epithelium. Since adhesion presents the first step in microbial invasion, blocking of the receptors may prevent or eliminate infection. Yeast cell wall polysaccharides are also able to adsorb mycotoxins, thus decreasing their toxic effect and mediating their removal from the organism. Commercial yeast polysaccharides (MTB100®, Alltech Inc.) have been shown to absorb a wide range of mycotoxins at low inclusion levels. Thus, especially if the ban on antibiotic growth promoters becomes global, use of yeast polysaccharides as natural growth stimulators becomes a very urgent and rewarding issue.     

The presence of EGF- and IGF-1-receptors in the small intestine of fetal, neonatal and weaned piglets

During development, gut morphology and functions change. Some of these are mediated by milk-borne factors, e.g. insulin-like growth factor-1 (IGF-1) and epidermal growth factor (EGF), of which the effects are in part dictated by the distribution of their receptors (R).

EGFR- and IGF-1R-immunoreactivity (IR) was evaluated in samples of the fetal, neonatal and weaned porcine small intestine.

EGFR-IR first appeared in the neonatal duodenum and was located basolaterally in villar and to a lesser extent in cryptal enterocytes. In weaned pigs, EGFR appeared apically in enterocytes with a region-dependent distribution along the villus–crypt axis. IGF-1R-IR was observed in smooth muscle cells in each age group. From the last trimester of gestation onward IGF-1R-IR was seen at the apical and basolateral side of villar enterocytes and in submucosal arterioles.

Thus, the age- and region-dependent presence of EGFR and IGF-1R has to be taken into account when evaluating effects of EGF and IGF-1 on growth or repair.     

Amino acid fortified diets for weanling pigs replacing fish meal and whey protein concentrate: Effects on growth,immune status,and gut health

Background

Limited availability of fish meal and whey protein concentrate increases overall feed costs. Availability of increased number of supplemental amino acids including Lys, Met, Thr, Trp, Val, and Ile allows replacing expensive protein supplements to reduce feed costs. This study was to evaluate the effect of replacing fish meal and/or whey protein concentrate in nursery diets with 6 supplemental amino acids on growth performance and gut health of post-weaning pigs. Treatments were 1) FM-WPC: diet with fish meal (FM) and whey protein concentrate (WPC); 2) FM-AA: diet with FM and crystalline amino acids (L-Lys, L-Thr, L-Trp, DL-Met, L-Val, and L-Ile); 3) WPC-AA: diet with WPC and crystalline amino acid; and 4) AA: diet with crystalline amino acid.

Results

Pigs in FM-AA, WPC-AA, and AA had greater (P < 0.05) ADG and gain:feed than pigs in FM-WPC during wk 1 (phase 1). Plasma insulin concentration of pigs in AA tended to be greater (P = 0.064) than that of FM-WPC at the end of wk 1(phase 1). Plasma concentrations of IgG in AA was lower (P < 0.05) compared with WPC-AA and FW, and FM-AA had lower (P < 0.05) IgG concentration than WPC-AA at the end of wk 1 (phase 1). Concentration of acetate in cecum digesta in FM-AA tended to be greater (P = 0.054) than that of FM-WPC and WPC-AA. Concentration of isovalerate in cecum digesta of pigs in FM-AA was greater (P < 0.05) than that of FW and WPC-AA.

Conclusions

This study indicates that use of 6 supplemental amino acids can replace fish meal and/or whey protein concentrate without adverse effects on growth performance, immune status, and gut health of pigs at d 21 to 49 of age. Positive response with the use of 6 supplemental amino acids in growth during the first week of post-weaning may due to increased plasma insulin potentially improving uptake of nutrients for protein synthesis and energy utilization. The replacement of fish meal and/or whey protein concentrate with 6 supplemental amino acids could decrease the crude protein level in nursery diets, and potentially lead to substantial cost savings in expensive nursery diets.