Heat stress affects fecal microbial and metabolic alterations of primiparous sows during late gestation

Responses of intestinal morphology, immunity, antioxidant status and cecal microbiota to the mixture of glycerol monolaurate and cinnamaldehyde in laying hens

This study was to determine the effects of the mixture of glycerol monolaurate and cinnamaldehyde (GCM) supplementation on the intestinal morphology, immunity, antioxidant status and cecal microbiota of laying hens. A total of 1,120 healthy laying hens (Jingfen-1 strain) at the age of 14 wk were randomly divided into 4 groups with 10 replicates of 28 layers in each and layers were fed diets containing 0 (control group), or 250, 500, and 1,000 mg/kg GCM for 12 wk. The results showed that dietary supplementation with GCM significantly increased intestinal villus height and villus height/crypt depth, duodenal villus area, total superoxide disumutase activities in the liver and jejunum, jejunal glutathione peroxidase activities while decreased duodenal and jejunal crypt depth, hydrogen peroxide content in the liver and jejunal malondialdehyde content of laying hens aging 28 wk (P < 0.05). Meanwhile, GCM addition significantly increased serum immunoglobulin A and immunoglobulin M concentration of layers at the age of 20, 24, and 28 wk (P < 0.05). Moreover, it was observed in the 16S rRNA sequencing that the addition of GCM elevated the abundance and diversity of gut microbiota in laying hens. The predominant bacteria from each group were Bacteroidota and Firmicutes at the phylum level and Bacteroides and Lactobacillus were the dominant genera. The composition and structure of cecal microflora were changed by the addition of GCM to the diet of laying hens. In conclusion, the addition of GCM (500-1,000 mg/kg diet) can improve intestinal morphology, immune function, intestinal and liver antioxidant status and intestinal flora of laying hens, thereby improving intestinal digestion and absorption capacity. These findings provide a new way to further explore the mechanism of GCM improving intestinal health.

Exertional heat stroke-induced changes in gut microbiota cause cognitive impairment in mice

BACKGROUND

The incidence of exertional heat stroke (EHS) escalates during periods of elevated temperatures, potentially leading to persistent cognitive impairment postrecovery. Currently, effective prophylactic or therapeutic measures against EHS are nonexistent.

METHODS

The selection of days 14 and 23 postinduction for detailed examination was guided by TEM of neuronal cells and HE staining of intestinal villi and the hippocampal regions. Fecal specimens from the ileum and cecum at these designated times were analyzed for changes in gut microbiota and metabolic products. Bioinformatic analyses facilitated the identification of pivotal microbial species and metabolites. The influence of supplementing these identified microorganisms on behavioral outcomes and the expression of functional proteins within the hippocampus was subsequently assessed.

RESULTS

TEM analyses of neurons, coupled with HE staining of intestinal villi and the hippocampal region, indicated substantial recovery in intestinal morphology and neuronal injury on Day 14, indicating this time point for subsequent microbial and metabolomic analyses. Notably, a reduction in the Lactobacillaceae family, particularly Lactobacillus murinus, was observed. Functional annotation of 16S rDNA sequences suggested diminished lipid metabolism and glycan biosynthesis and metabolism in EHS models. Mice receiving this intervention (EHS + probiotics group) exhibited markedly reduced cognitive impairment and increased expression of BDNF/TrKB pathway molecules in the hippocampus during behavioral assessment on Day 28.

CONCLUSION

Probiotic supplementation, specifically with Lactobacillus spp., appears to mitigate EHS-induced cognitive impairment, potentially through the modulation of the BDNF/TrKB signaling pathway within the hippocampus, illustrating the therapeutic potential of targeting the gut-brain axis.

Folic Acid and Taurine Alleviate the Impairment of Redox Status, Immunity, Rumen Microbial Composition and Fermentation of Lambs under Heat Stress

The aim of this study was to investigate if the supplementation of folic acid and taurine can relieve the adverse effects of different levels of heat stress (HS) on growth performance, physiological indices, antioxidative capacity, immunity, rumen fermentation and microbiota. A total of 24 Dorper × Hu crossbred lambs (27.51 ± 0.96 kg) were divided into four groups: control group (C, 25 °C), moderate HS group (MHS, 35 °C), severe HS group (SHS, 40 °C), and the treatment group, under severe HS (RHS, 40 °C, 4 and 40 mg/kg BW/d coated folic acid and taurine, respectively). Results showed that, compared with Group C, HS significantly decreased the ADG of lambs (p < 0.05), and the ADG in the RHS group was markedly higher than in the MHS and SHS group (p < 0.05). HS had significant detrimental effects on physiological indices, antioxidative indices and immune status on the 4th day (p < 0.05). The physiological indices, such as RR and ST, increased significantly (p < 0.05) with the HS level and were significantly decreased in the RHS group, compared to the SHS group (p < 0.05). HS induced the significant increase of MDA, TNF-α, and IL-β, and the decrease of T-AOC, SOD, GPx, IL-10, IL-13, IgA, IgG, and IgM (p < 0.05). However, there was a significant improvement in these indices after the supplementation of folic acid and taurine under HS. Moreover, there were a significant increase in Quinella and Succinivibrio, and an evident decrease of the genera Rikenellaceae_RC9_gut_group and Asteroleplasma under HS (p < 0.05). The LEfSe analysis showed that the genera Butyrivibrio, Eubacterium_ventriosum_group, and f_Bifidobacteriaceae were enriched in the MHS, SHS and RHS groups, respectively. Correlated analysis indicated that the genus Rikenellaceae_RC9_gut_group was positively associated with MDA, while it was negatively involved in IL-10, IgA, IgM, and SOD (p < 0.05); The genus Anaeroplasma was positively associated with the propionate and valerate, while the genus Succinivibrio was negatively involved in TNF-α (p < 0.05). In conclusion, folic acid and taurine may alleviate the adverse effects of HS on antioxidant capacity, immunomodulation, and rumen fermentation of lambs by inducing changes in the microbiome that improve animal growth performance.

Inflammatory response in dairy cows caused by heat stress and biological mechanisms for maintaining homeostasis

Climate change increases global temperatures, which is lethal to both livestock and humans. Heat stress is known as one of the various livestock stresses, and dairy cows react sensitively to high-temperature stress. We aimed to better understand the effects of heat stress on the health of dairy cows and observing biological changes. Individual cows were divided into normal (21-22 °C, 50-60% humidity) and high temperature (31-32 °C, 80-95% humidity), respectively, for 7-days. We performed metabolomic and transcriptome analyses of the blood and gut microbiomes of feces. In the high-temperature group, nine metabolites including linoleic acid and fructose were downregulated, and 154 upregulated and 72 downregulated DEGs (Differentially Expressed Genes) were identified, and eighteen microbes including Intestinimonas and Pseudoflavonifractor in genus level were significantly different from normal group. Linoleic acid and fructose have confirmed that associated with various stresses, and functional analysis of DEG and microorganisms showing significant differences confirmed that high-temperature stress is related to the inflammatory response, immune system, cellular energy mechanism, and microbial butyrate production. These biological changes were likely to withstand high-temperature stress. Immune and inflammatory responses are known to be induced by heat stress, which has been identified to maintain homeostasis through modulation at metabolome, transcriptome and microbiome levels. In these findings, heat stress condition can trigger alteration of immune system and cellular energy metabolism, which is shown as reduced metabolites, pathway enrichment and differential microbes. As results of this study did not include direct phenotypic data, we believe that additional validation is required in the future. In conclusion, high-temperature stress contributed to the reduction of metabolites, changes in gene expression patterns and composition of gut microbiota, which are thought to support dairy cows in withstanding high-temperature stress via modulating immune-related genes, and cellular energy metabolism to maintain homeostasis.

Importance of dietary supplementation of soluble and insoluble fibers to sows subjected to high ambient temperatures during late gestation and effects on lactation performance

Heat stress adversely affects sows' performance, which can be improved by applying proper nutritional strategies. This study was conducted to investigate the interactive effects of dietary fiber levels and sources on sows' reproductive performance, metabolic response during gestation, and the carry-over influence on litter performance in the lactation period during heat stress (average room temperature of 27.1 °C). Fifty-four multiparous sows (Landrace × Yorkshire; initial body weight of 236.3 ± 16 kg; 2, 3 and 4 parities) at d 90 of gestation were assigned to a 2 × 3 factorial arrangement (9 sows/treatment), involving 2 dietary fiber levels (4.5% and 6% crude fiber) and 3 dietary fiber sources (wheat bran [WB], palm kernel meal [PK], and beet pulp [BP]). Sows fed the BP diet had highest (P < 0.01) feed intake and constipation index and lowest (P < 0.01) farrowing duration. Piglet weight (P = 0.041) and litter weight (P < 0.01) at weaning were higher in sows in the BP treatment compared to PK treatment. Sows in the BP treatment showed the greatest (P < 0.01) digestibility of crude protein and neutral detergent fiber. The fecal concentration of acetate was the lowest (P < 0.01) in the PK treatment. Total short-chain fatty acid production was increased in the WB and BP treatments compared with the PK. Sows in the BP treatment showed the lowest (P = 0.036) hair cortisol. The blood insulin concentration of sows was higher (P = 0.026) in the high fiber (6%) treatment compared with the low fiber (4.5%) treatment at 90 min and 120 min after the meal. The concentration of phthalic acid, succinic acid, phenylethylamine, hydrocinnamic acid, iron, linoleic acid, glycerol, ketone, and formamide were increased (P < 0.05) in the BP treatment compared with the WB. The BP treatment with high soluble fiber content improved the constipation index, farrowing duration, and litter performance, while high insoluble fibers increased sows comfort and reduced stress factors including respiratory rate and rectal temperature. Therefore, both soluble and insoluble sources of fiber are necessary to be added to the diet of gestating sows.

Maternal Malic Acid May Ameliorate Oxidative Stress and Inflammation in Sows through Modulating Gut Microbiota and Host Metabolic Profiles during Late Pregnancy

Sows suffer oxidative stress and inflammation induced by metabolic burden during late pregnancy, which negatively regulates reproductive and lactating performances. We previously found that L-malic acid (MA) alleviated oxidative stress and inflammation and improved reproductive performances in sows. However, the mechanism underlying the MA's positive effects remains unexplored. Here, twenty Large White × Landrace sows with similar parity were randomly divided into two groups and fed with a basal diet or a diet supplemented with 2% L-malic acid complex from day 85 of gestation to delivery. The gut microbiome, fecal short-chain fatty acids, and untargeted serum metabolome were determined. Results showed that Firmicutes, Bacteroidota, and Spirochaetota were the top abundant phyla identified in late pregnancy for sows. Maternal MA supplementation modulated the composition but not the richness and diversity of gut microbiota during late pregnancy. Correlation analysis between gut microbiota and antioxidant capacity (or inflammation indicators) revealed that unclassified_f_Ruminococcaceae, unclassified_f_Lachnospiraceae, UCG-002, norank_f_norank_o_RF3, and Lactobacillus might play a role in anti-oxidation, and Lachnospiraceae_XPB1014_group, Lachnospiraceae_NK4A136_group, UCG-002, unclassified_f_Ruminococcaceae, Candidatus_Soleaferrea, norank_f_UCG-010, norank_f_norank_o_RF39, and unclassified_f_Lachnospiraceae might be involved in the anti-inflammatory effect. The improved antioxidant and inflammation status induced by MA might be independent of short chain fatty acid changes. In addition, untargeted metabolomics analysis exhibited different metabolic landscapes of sows in the MA group from in the control group and revealed the contribution of modified amino acid and lipid metabolism to the improved antioxidant capacity and inflammation status. Notably, correlation results of gut microbiota and serum metabolites, as well as serum metabolites and antioxidant capacity (or inflammation indicators), demonstrated that differential metabolism was highly related to the fecal microorganisms and antioxidant or inflammation indicators. Collectively, these data demonstrated that a maternal dietary supply of MA can ameliorate oxidative stress and inflammation in sows through modulating gut microbiota and host metabolic profiles during late pregnancy.

Improvement of weanling pigs immune status and metabolic condition using ultraweak light

Weaning stress is the most common issue in swine farms, which increases mortality and morbidity. The use of artificial light is an option for modifying the immune system and metabolic pathways. This study aimed to evaluate the influence of ultraweak light (Photonia) on growth performance, immune system and metabolism of weanling pigs, and the carry-over effect on the growth performance in postweanling growing stages. A total of 30 weaned pigs with an average initial body weight of 7.06 ± 0.11 kg (age: 21 days) were allotted two treatments (Control and Photonia) with 15 replicates. The pelleted form diets were prepared for pigs in three phases including phase 1 (Days 0-14), phase 2 (Days 15-28) and phase 3 (Days 29-48). The gain-to-feed ratio (G:F) of pigs was significantly greater in the Photonia treatment. On Day 28, a higher concentration of immunoglobin A (IgA) (p < 0.01) and IgG (p < 0.01) was observed in the Photonia pigs. On Day 48, the Photonia treatment showed a greater serum IgA (p < 0.01) and IgG (p < 0.05). The concentration of interleukin (IL)-6 was decreased (p < 0.05) in the Photonia treatment. At Day 48, the concentrations of tumour necrotic factor-α, IL-1β and IL-6 in serum were decreased (p < 0.05) in pigs in the Photonia treatment. Metabolic pathways analysis showed that the Photonia treatment increased the d-glutamine, d-glutamate, alanine, aspartate, glutamate and phenylalanine compared with the control treatment. In conclusion, the use of Photonia for weanling pigs is recommended due to improved G:F, immune status and activation of amino acids metabolic pathways including d-glutamine, d-glutamate, alanine, aspartate, glutamate and phenylalanine.

Dietary Chinese herbal mixture supplementation improves production performance by regulating reproductive hormones, antioxidant capacity, immunity, and intestinal health of broiler breeders

Chinese herbs have been used as feed additives and are commonly utilized in domestic intensive livestock farming. However, their impact on the production performance and intestinal health of broiler breeders has yet to be thoroughly explored. This study aimed to evaluate the effects of a Chinese herbal mixture (CHM) on the production performance of broiler breeders in terms of reproductive hormones, antioxidant capacity, immunity, and intestinal health of broiler breeders. A total of 336 thirty-wk-old hens were randomly allotted to 4 groups with 6 replicates of fourteen hens each, which fed a basal diet supplemented with 0 (CON), 500 (CHM500), 1,000 (CHM1000), and 1,500 (CHM1500) mg/kg CHM for 56 days, respectively. Our results showed that dietary supplementation with CHM1000 increased the laying rate and number of SYF and decreased the feed conversion ratio (P < 0.05). All CHM groups increased oviduct and ovarian indexes, serum E2 and T-AOC levels, and decreased serum TG and MDA levels compared with CON (P < 0.05). In comparison to the CON group, the CHM1000 and CHM1500 groups increased serum ALB, IgM, and IL-10 levels, whereas the CHM1000 group also increased serum TP and SOD levels, and the CHM1500 group increased serum P and decreased serum TNF-α (P < 0.05). The addition of CHM increased FSHR expressions in the ovary, Claudin-1 expressions in the jejunum, and SOD1 expressions in the liver and ovary, but decreased the mRNA expressions of INH in the ovary as well as IL-2 and IL-6 expressions in the jejunum (P < 0.05). Moreover, CHM500 and CHM1000 groups increased CAT, GPx, and HO-1 expression in the ovary, and SOD1 and GPx expression in the jejunum, while decreasing IL-17A expression in the jejunum (P < 0.05). In addition, CHM1000 and CHM1500 groups increased villus height, VCR, and the mRNA expressions of Nrf2, HO-1, Occludin, and MUC2 in the jejunum, and IL-10 expression in the ovary, while decreasing IL-2 and IL-17A expression in the ovary, in addition to increasing GPx, Nrf2, HO-1, NQO1, and IL-10 expression in the liver (P < 0.05). Supplementation with CHM1000 increased ESR-α, ESR-β, GnRH, Nrf2, and NQO1 expression in the ovary, but decreased IFN-γ expression in the ovary as well as crypt depth in the jejunum (P < 0.05). Supplementing CHM1500 increased NQO1 and ZO-1 expression in the jejunum and decreased IL-2 in the liver (P < 0.05). The high-throughput sequencing results showed that dietary CHM1000 supplementation altered the composition of the intestinal microbiota, as evidenced by the regulation of the genera Lactobacillus, Faecalibacterium, and Phascolarctobacterium. PICRUSt analysis revealed that metabolic pathways of bacterial chemotaxis, butanoate metabolism, and synthesis and degradation of ketone bodies were enriched in the CHM1000 group. Spearman's correlation analysis indicated that the differentiated genera were significantly associated with the production performance, serum hormone, and gut barrier-related genes. Taken together, supplementation of CHM, especially at 1,000 mg/kg, could improve production performance by regulating reproductive hormones, antioxidant capacity, immunity, and intestinal health of broiler breeders, and maybe provide insights into its application as a potential feed additive to promote the performance of broiler breeders.

Prophylactic influences of prebiotics on gut microbiome and immune response of heat-stressed broiler chickens

Climatic changes and elevated ambient temperature are significant environmental stressors with a negative impact on birds' physiological, immunological, and behavioral status, increasing their susceptibility to stressors and immunosuppression and consequently increasing intestinal permeability (leaky gut). Prebiotics have been utilized to stop or diminish the harmful effects of stress in chickens. We aimed to evaluate the role of mannan-oligosaccharides, and beta-D-glucan prebiotics supplements in drinking water against experimentally induced heat stress (HS) on broiler chickens and study their impact on birds' performance, gut microbiome, and immune response. A total of 120 1-day-old Ross broiler chicks were allocated into four groups (30 birds/group), and each group was subdivided into triplicates (10 birds each). The experimental groups were classified as follows; the 1st (G1) control birds, the 2nd (G2) birds exposed experimentally to HS, the 3rd (G3) birds administered prebiotics in drinking water without exposure to HS, and the 4th (G4) birds exposed to HS and administered prebiotics in drinking water. After each vaccination, blood samples and serum samples were collected to evaluate the birds' immune status. Fecal samples were also collected for the molecular evaluation of the gut microbiome based on the genetic analyses and sequencing of 16S rRNA gene. The results showed that HS has reduced the birds' performance and badly affected the birds' immune response and gut microbiome. However, the addition of prebiotics to drinking water, with or without stress, enhanced the growth rate, maintained a normal gut microbiome, and improved immune parameters. Moreover, the usage of prebiotics improved the chicken gut microbiome and alleviated the negative effect of heat stress. Administering prebiotics significantly (p < 0.05) increased the relative abundance of beneficial bacteria and eradicated pathogenic ones in the birds' gut microbiome. Prebiotics showed a positive effect on the gut microbiome and the immune status of chickens under HS in addition to their efficacy as a growth promoter.

Indicators of improved gestation housing of sows. Part II: Effects on physiological measures, reproductive performance and health of the offspring

Prenatal stress is the mechanism through which poor welfare of pregnant sows has detrimental effects on the health and resilience of their piglets. We compared two gestation housing systems (IMPROVED versus [conventional] CONTROL) in terms of sow stress and welfare indicators and sought to determine whether potential benefits to the sows would translate into improved offspring health. Sows were mixed into 12 stable groups (six groups per treatment, 20 sows per group) 29 days post-service in pens with free-access, full-length individual feeding/lying-stalls. CONTROL pens had fully slatted concrete floors, with two blocks of wood and two chains suspended in the group area. IMPROVED pens were the same but with rubber mats and manila rope in each stall, and straw provided in three racks in the group area. Saliva was collected from each sow on day 80 of pregnancy and analysed for haptoglobin. Hair cortisol was measured in late gestation. Sows' right and left eyes were scored for tear staining in mid lactation and at weaning. Numbers of piglets born alive, dead, mummified, and total born were recorded. Piglets were weighed and scored for vitality and intra-uterine growth restriction (IUGR) at birth. Presence of diarrhoea in farrowing pens was scored every second day throughout the suckling period. IMPROVED sows had lower haptoglobin levels and tear-stain scores during lactation. IMPROVED sows produced fewer mummified piglets, and these had significantly lower IUGR scores, and scored lower for diarrhoea than piglets of CONTROL sows. Hence, improving sow welfare during gestation improved the health and performance of their offspring.

Heat Stress-Induced Intestinal Barrier Impairment: Current Insights into the Aspects of Oxidative Stress and Endoplasmic Reticulum Stress

Heat stress (HS) occurs when the sensible temperature of animals exceeds their thermoregulatory capacity, a condition that exerts a detrimental impact on health and growth. The intestinal tract, as a highly sensitive organ, has been shown to respond to HS by exhibiting mucosal injury, intestinal leakage, and disturbances in the gut microbiota. Oxidative stress and endoplasmic reticulum stress (ERS) are both potential outcomes of long-term exposure to high temperatures and have been linked to apoptosis, autophagy, and ferroptosis. In addition, HS alters the composition of the gut microbiota accompanied by changed levels of bacterial components and metabolites, rendering the gut more vulnerable to stress-related injury. In this review, we present recent advances in mechanisms of oxidative stress-associated ERS in response to HS, which is destructive to intestinal barrier integrity. The involvement of autophagy and ferroptosis in ERS was highlighted. Further, we summarize the relevant findings regarding the engagement of gut microbiota-derived components and metabolites in modulation of intestinal mucosal injury induced by HS.

State of the art in research on the gut-liver and gut-brain axis in poultry

The relationship between the intestines and their microbiota, the liver, and the neuronal system is called the gut-liver-brain axis. This relationship has been studied and observed for a relatively short time but is considered in the development of research focused on, e.g., liver diseases and intestinal dysbiosis. The role of the gut microbiota in this relationship is crucial, as it acts on poultry's performance and feed utilization, affecting meat and egg quality. The correct composition of the intestinal microbiota makes it possible to determine the essential metabolic pathways and biological processes of the individual components of the microbiota, allowing further speculation of the role of microbial populations on internal organs such as the liver and brain in the organism. The gut microbiota forms a complex, dense axis with the autonomic and enteric nervous systems. The symbiotic relationship between the liver and gut microbiota is based on immune, metabolic and neuroendocrine regulation, and stabilization. On the other hand, the gut-brain axis is a bidirectional interaction and information transfer system between the gastrointestinal tract and the central nervous system. The following paper will discuss the current state of knowledge of the gut-liver-brain axis of poultry, including factors that may affect this complex relationship.

The Effect of Supplementation with Betaine and Zinc on In Vitro Large Intestinal Fermentation in Iberian Pigs under Heat Stress

We investigated the effects of betaine and zinc on the in vitro fermentation of pigs under heat stress (HS). Twenty-four Iberian pigs (43.4 ± 1.2 kg) under HS (30 °C) were assigned to treatments for 4 weeks: control (unsupplemented), betaine (5 g/kg), and zinc (0.120 g/kg) supplemented diet. Rectal content was used as the inoculum in 24-hincubations with pure substrates (starch, pectin, inulin, cellulose). Total gas, short-chain fatty acid (SCFA), and methane production and ammonia concentration were measured. The abundance of total bacteria and several bacterial groups was assessed. Betaine increased the acetate production with pectin and inulin, butyrate production with starch and inulin, and ammonia concentration, and decreased propionate production with pectin and inulin. The abundance of Bifidobacterium and two groups of Clostridium decreased with betaine supplementation. Zinc decreased the production of SCFA and gas with starch and inulin, associated with diminished bacterial activity. Propionate production decreased with starch, pectin, and inulin while butyrate production increased with inulin, and isoacid production increased with cellulose and inulin in pigs supplemented with zinc. The ammonia concentration increased for all substrates. The Clostridium cluster XIV abundance decreased in pigs fed zinc supplemented diets. The results reported were dependent on the substrate fermented, but the augmented butyrate production with both betaine and zinc could be of benefit for the host.

Influence of fiber type and carbohydrase supplementation on nutrient digestibility, energy and nitrogen balance, and physiology of sows at mid and late gestation

Carbohydrase supplementation in grow-finish pig diets improves energy, nutrient digestibility, and gastrointestinal function, but their efficacy in gestation diets is understudied. The experimental objective was to evaluate the efficacy of a multicarbohydrase to improve digestion, energetics, and various physiological functions in gestating sows fed soluble and insoluble fiber diets. On day 28 of gestation, 36 sows (186 ± 4.6 kg body weight), blocked by parity, were randomly assigned to a 2 × 2 factorial arrangement of dietary treatments (n = 9). Factors included fiber type of insoluble (IF; 20% dried distiller grains with solubles) or soluble fiber (SF; 20% sugar beet pulp) and with (+) or without (-) enzyme (0.05%, Rovabio Advance P10; Adisseo, Antony, France). Diets were fed from days 28 to 109 of gestation at a feeding level of 2.1 kg (SID-Lys 11 g/d and 4.5 net energy-Mcal/d). Two separate 9-d metabolism periods were conducted on days 50 to 59 (mid) and 99 to 108 (late) of gestation. During each period, days 1 to 3 served as an adaptation period, days 4 to 7 total urine and feces were collected (96-h) and followed by a 48-h lactulose-mannitol study. Serum and plasma were collected on days 50 and 99. Data were analyzed as repeated records using a linear mixed model with block as a random effect and fiber type, enzyme, and period and their interactions as fixed effects. Sows fed SF+ had increased serum IL-1ra (Fiber × Enzyme P = 0.035), and IL-2 (Fiber × Enzyme P = 0.042). In the presence of IF, multicarbohydrases increased serum lipopolysaccharide-binding protein, but not when supplemented with SF (Fiber × Enzyme P = 0.028). Circulating IL-8 and TNF-α were decreased in sows fed multicarbohydrases (P < 0.05). Multicarbohydrase supplementation increased the apparent total tract digestibility (ATTD) of gross energy (GE), dry matter, and neutral detergent fiber by 2.8%, 3.4%, and 8.3%, respectively (P < 0.05). Compared to IF-, the ATTD of hemicellulose was 5.3% greater in sows fed IF+ but did not differ from SF- and SF+ (Fiber × Enzyme P = 0.037). Sows fed IF+ had the greatest ATTD of insoluble dietary fiber (Fiber × Enzyme P = 0.011). Sows fed multicarbohydrases excreted less energy in their urine (519 vs. 469 GE kcal/d; Enzyme P = 0.033) and in their feces (985 vs. 900 GE kcal/d; Enzyme P = 0.003). This resulted in an improvement in both digestible energy (Enzyme P < 0.01) and metabolizable energy (Enzyme P = 0.041), irrespective of fiber type. In conclusion, multicarbohydrase supplementation increased the digestibility and energetic contribution of fiber, irrespective of adaptation time or fiber type, but modulation of inflammatory responses was unique to dietary fiber type.

Effect of fermented heat-treated rice bran on performance and possible role of intestinal microbiota in laying hens

Rice bran is a high-quality and renewable livestock feed material rich in nutrients and bioactive substances. To investigate the effects of dietary supplementation with fermented heat-treated rice bran on the performance, apparent digestibility of nutrients, cecal microbiota and metabolites in laying hens, a total of 128 18-week-old Hy-Line brown layers were randomly assigned to four treatment groups: 2.5% HRB (basal diet contained 2.5% heat-treated rice bran), 5.0% HRB (5.0% heat-treated rice bran), 2.5% FHRB (2.5% fermented heat-treated rice bran), 5.0% FHRB (5.0% fermented heat-treated rice bran). Results showed that FHRB supplementation significantly increased the average daily feed intake (ADFI) during 25-28 weeks, and improved apparent digestibility of dry matter (DM), crude protein (CP), ether extract (EE) and crude fiber (CF) in laying hens. Moreover, feeding 5.0% of HRB and FHRB resulted higher egg production (EP) and average egg weight (AEW) during the feeding period, and decreased the feed conversion ratio (FCR) during 21 to 28 weeks. The alpha and beta diversity indices indicated that FHRB altered the cecal microbiota. In particular, dietary supplementation with FHRB significantly increased the relative abundances of Lachnospira and Clostridium. Compared with the 2.5% level of supplementation, supplementing 5.0% HRB and 5.0% FHRB increased the relative abundances of Firmicutes, Ruminococcus and Peptococcus, and lowered the relative abundance of Actinobacteria. Furthermore, dietary FHRB supplementation significantly increased the concentration of short-chain fatty acids in cecum and changed the overall metabolome. The results of correlation analysis showed a close interaction between cecal microbiota, metabolites and apparent digestibility of nutrients. Taken together, we revealed that FHRB supplementation can induce characteristic structural and metabolic changes in the cecal microbiome, which could potentially promote nutrient digestion and absorption, and improve the production performance of laying hens.

Alteration of gut microbiota after heat acclimation may reduce organ damage by regulating immune factors during heat stress

Introduction

Heat-related illnesses can lead to morbidity, which are anticipated to increase frequency with predictions of increased global surface temperatures and extreme weather events. Although heat acclimation training (HAT) could prevent heat-related diseases, the mechanisms underlying HAT-promoting beneficial changes in organ function, immunity, and gut microbes remain unclear.

Methods

In the current study, we recruited 32 healthy young soldiers and randomly divided them into 4 teams to conduct HATs for 10 days: the equipment-assisted training team at high temperature (HE); the equipment-assisted training team under normal hot weather (NE); the high-intensity interval training team at high temperature (HIIT), and the control team without training. A standard heat tolerance test (HTT) was conducted before (HTT-1st) and after (HTT-2nd) the training to judge whether the participants met the heat acclimation (HA) criteria.

Results

We found that the participants in both HE and NE teams had significantly higher acclimation rates (HA/total population) than whom in the HIIT team. The effects of HAT on the participants of the HE team outperformed that of the NE team. In the HA group, the differences of physiological indicators and plasma organ damage biomarkers (ALT, ALP, creatinine, LDH, α-HBDH and cholinesterase) before and after HTT-2nd were significantly reduced to those during HTT-1st, but the differences of immune factors (IL-10, IL-6, CXCL2, CCL4, CCL5, and CCL11) elevated. The composition, metabolism, and pathogenicity of gut microbes changed significantly, with a decreased proportion of potentially pathogenic bacteria (Escherichia-Shigella and Lactococcus) and increased probiotics (Dorea, Blautia, and Lactobacillus) in the HA group. Training for a longer time in a high temperature and humidity showed beneficial effects for intestinal probiotics.

Conclusion

These findings revealed that pathogenic gut bacteria decrease while probiotics increase following HA, with elevated immune factors and reduced organ damage during heat stress, thereby improving the body's heat adaption.

Gastro-Intestinal Microbiota in Equines and Its Role in Health and Disease: The Black Box Opens

Horses are large non-ruminant herbivores and rely on microbial fermentation for energy, with more than half of their maintenance energy requirement coming from microbial fermentation occurring in their enlarged caecum and colon. To achieve that, the gastro-intestinal tract (GIT) of horses harbors a broad range of various microorganisms, differing in each GIT segment, which are essential for efficient utilization of feed, especially to use nutrients that are not or little degraded by endogenous enzymes. In addition, like in other animal species, the GIT microbiota is in permanent interplay with the host's cells and is involved in a lot of functions among which inflammation, immune homeostasis, and energy metabolism. As for other animals and humans, the horse gut microbiome is sensitive to diet, especially consumption of starch, fiber, and fat. Age, breeds, stress during competitions, transportation, and exercise may also impact the microbiome. Because of its size and its complexity, the equine GIT microbiota is prone to perturbations caused by external or internal stressors that may result in digestive diseases like gastric ulcer, diarrhea, colic, or colitis, and that are thought to be linked with systemic diseases like laminitis, equine metabolic syndrome or obesity. Thus, in this review we aim at understanding the common core microbiome -in terms of structure and function- in each segment of the GIT, as well as identifying potential microbial biomarkers of health or disease which are crucial to anticipate putative perturbations, optimize global practices and develop adapted nutritional strategies and personalized nutrition.

Untargeted Metabolomics Pilot Study Using UHPLC-qTOF MS Profile in Sows' Urine Reveals Metabolites of Bladder Inflammation

Urinary tract infections (UTI) of sows (characterized by ascending infections of the urinary bladder (cyst), ureters, and renal pelvis), are major health issues with a significant economic impact to the swine industry. The current detection of UTI incidents lacks sensitivity; thus, UTIs remain largely under-diagnosed. The value of metabolomics in unraveling the mechanisms of sow UTI has not yet been established. This study aims to investigate the urine metabolome of sows for UTI biomarkers. Urine samples were collected from 58 culled sows from a farrow-to-finish herd in Greece. Urine metabolomic profiles in 31 healthy controls and in 27 inflammatory ones were evaluated. UHPLC-qTOF MS/MS was applied for the analysis with a combination of multivariate and univariate statistical analysis. Eighteen potential markers were found. The changes in several urine metabolites classes (nucleosides, indoles, isoflavones, and dipeptides), as well as amino-acids allowed for an adequate discrimination between the study groups. Identified metabolites were involved in purine metabolism; phenylalanine; tyrosine and tryptophan biosynthesis; and phenylalanine metabolism. Through ROC analysis it was shown that the 18 identified metabolite biomarkers exhibited good predictive accuracy. In summary, our study provided new information on the potential targets for predicting early and accurate diagnosis of UTI. Further, this information also sheds light on how it could be applied in live animals.

Heat stress in pigs and broilers: role of gut dysbiosis in the impairment of the gut-liver axis and restoration of these effects by probiotics, prebiotics and synbiotics

Heat stress is one of the most challenging stressors for animal production due to high economic losses resulting from impaired animal’s productivity, health and welfare. Despite the fact that all farm animal species are susceptible to heat stress, birds and pigs are particularly sensitive to heat stress due to either lacking or non-functional sweat glands. Convincing evidence in the literature exists that gut dysbiosis, a term used to describe a perturbation of commensal gut microbiota, develops in broilers and pigs under heat stress. Owing to the protective role of commensal bacteria for the gut barrier, gut dysbiosis causes a disruption of the gut barrier leading to endotoxemia, which contributes to the typical characteristics of heat stressed broilers and growing and growing-finishing pigs, such as reduced feed intake, decreased growth and reduced lean carcass weight. A substantial number of studies have shown that feeding of probiotics, prebiotics and synbiotics is an efficacious strategy to protect broilers from heat stress-induced gut barrier disruption through altering the gut microbiota and promoting all decisive structural, biochemical, and immunological elements of the intestinal barrier. In most of the available studies in heat stressed broilers, the alterations of gut microbiota and improvements of gut barrier function induced by feeding of either probiotics, prebiotics or synbiotics were accompanied by an improved productivity, health and/or welfare when compared to non-supplemented broilers exposed to heat stress. These findings indicate that the restoration of gut homeostasis and function is a key target for dietary interventions aiming to provide at least partial protection of broilers from the detrimental impact of heat stress conditions. Despite the fact that the number of studies dealing with the same feeding strategy in heat stressed pigs is limited, the available few studies suggest that feeding of probiotics might also be a suitable approach to enhance productivity, health and welfare in pigs kept under heat stress conditions. 

N-Carbamylglutamate Improves Reproductive Performance and Alters Fecal Microbiota and Serum Metabolites of Primiparous Sows during Gestation after Fixed-Time Artificial Insemination

N-carbamylglutamate (NCG) supplementation during gestation improves reproductive performance in sows after conventional artificial insemination. However, whether NCG can improve reproductive performance and change fecal microbiota and serum metabolite levels during pregnancy in sows after fixed-time artificial insemination (FTAI) remains unclear. Two hundred multiparous sows were assigned a diet from mating until farrowing: control (corn−soybean meal) or NCG supplementation (0.05% NCG). At days 30, 70, and 110 of gestation and after farrowing, maternal microbial diversity and serum metabolites were studied. Supplementation of NCG increased the number of piglets born alive and the litter weight (all p < 0.05) and altered the fetal microbial community during gestation. Some genera were particularly abundant at different time points during gestation and after farrowing, but none were commonly abundant across all four time points. Metabolic analysis revealed that NCG supplementation significantly increased the serum concentrations of NCG, ferulic acid, cinnamoylglycine, 3-phenyllactic acid, and gamma-glutamylglutamic acid in the NCG group compared with levels in the control group. Our results reveal that NCG supplementation during gestation improves reproductive performance in sows after FTAI, exerting both direct (increased serum NCG levels) and indirect effects (altered intestinal microbiome and serum metabolites) on sow reproduction and, ultimately, improving placental and fetal development.

Effects of Dietary Supplementation of Solubles from Shredded, Steam-Exploded Pine Particles on the Performance and Cecum Microbiota of Acute Heat-Stressed Broilers

Heat stress (HS) negatively influences livestock productivity, but it can be, at least in part, mitigated by nutritional interventions. One such intervention is to use byproducts from various sources that are likely to be included in the consumer chain. Thus, the present study investigated the effects of dietary supplementation of solubles from shredded, steam-exploded pine particles (SSPPs) on the performance and cecum microbiota in broilers subjected to acute HS. One-week-old Ross 308 broilers (n = 108) were fed 0%, 0.1%, or 0.4% SSPP in their diets. On the 37th day, forty birds were allocated to one of four groups; namely, a group fed a control diet without SSPPs at thermoneutral temperature (NT) (0% NT) and acute heat-stressed birds with 0% (0% HS), 0.1% (0.1% HS), and 0.4% (0.4% HS) SSPP-supplemented diets. The NT was maintained at 21.0 °C, while the HS room was increased to 31 °C. The final BW, percent difference in body weight (PDBW), and feed intake (FI) were lower in HS birds, but PDBW was reversely associated with dietary SSPP. Similarly, HS birds had a higher rectal temperature (RT) and ΔT in comparison to birds kept at NT. The FI of SSPP-supplemented birds was not significant, indicating lower HS effects. Plasma triglyceride was decreased in HS birds but not affected in 0.1% HS birds in comparison to 0% NT birds. OTUs and Chao1 were increased by 0.1% HS compared to 0% NT. Unweighted Unifrac distances for 0.1% HS were different from 0% NT and 0.4% HS. The favorable bacterial phylum (Tenericutes) and genera (Faecalibacterium and Anaerofustis) were increased, while the pathogenic genus (Enterococcus) was decreased, in SSPP-supplemented birds. In sum, production performances are negatively affected under acute HS. Dietary supplementation of SSPPs is beneficial for improving community richness indices and unweighted Unifrac distances, and it enhanced the advantageous bacterial phyla and reduced virulent genera and triglyceride hydrolysis in acute HS broilers. Our results indicate that dietary SSPPs modulates the microbial profile of the cecum while resulting in relatively less weight loss and lower rectal temperature compared to control.

Effect of Chinese Herbs on Serum Biochemical Parameters, Immunity Indices, Antioxidant Capacity and Metabolomics in Early Weaned Yak Calves

Chinese traditional herbs are used widely as feed supplements to improve the immune response and antioxidant capacity of livestock. Twenty early-weaned 4-month-old yak calves (72.3 ± 3.65 kg) were divided randomly into four groups (n = 5 per group); three groups were provided with supplementary 80 mL/kg DMI of the root water extracts of either Angelica sinensis, Codonopsis pilosula or Glycyrrhiza uralensis, and one group (control) was not provided with a supplement. Compared to control calves, calves consuming the three herbal extracts increased serum concentrations of albumin (ALB) and glutathione peroxidase (GSH-Px), but decreased serum concentrations of free fatty acids (FFAs) and malondialdehyde (MDA) (p < 0.05). Calves consuming A. sinensis decreased (p < 0.05) serum concentration of total cholesterol (TC), and increased (p < 0.05) serum concentration of total proteins (TP). Serum FFA concentrations increased (p = 0.004) linearly with time in the control group, but not in the groups consuming herbs. Serum metabolomic data demonstrated that A. sinensis and C. pilosula regulate mainly amino acid metabolism, while G. uralensis regulates mainly carbon and amino acid metabolism. It was concluded that the three herbal root extracts, as dietary supplements, improved energy and nitrogen metabolism, and enhanced the antioxidant capacity of yak calves.

UHPLC-MS/MS-Based Metabolomics and Clinical Phenotypes Analysis Reveal Broad-Scale Perturbations in Early Pregnancy Related to Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is the most common metabolic disturbance during pregnancy, with adverse effects on both mother and fetus. The establishment of early diagnosis and risk assessment model is of great significance for preventing and reducing adverse outcomes of GDM. In this study, the broad-scale perturbations related to GDM were explored through the integration analysis of metabolic and clinical phenotypes. Maternal serum samples from the first trimester were collected for targeted metabolomics analysis by using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Statistical analysis was conducted based on the levels of the 184 metabolites and 76 clinical indicators from GDM women ( $n$  =60) and matched healthy controls ( $n$  =90). Metabolomics analysis revealed the down-regulation of fatty acid oxidation in the first trimester of GDM women, which was supposed to be related to the low serum level of dehydroepiandrosterone.While the significantly altered clinical phenotypes were mainly related to the increased risk of cardiovascular disease, abnormal iron metabolism, and inflammation. A phenotype panel established from the significantly changed serum indicators can be used for the early prediction of GDM, with the area under the receiver-operating characteristic curve (ROC) 0.83. High serum uric acid and C-reaction protein levels were risk factors for GDM independent of body mass indexes, with ORs 4.76 (95% CI: 2.08-10.90) and 3.10 (95% CI: 1.38-6.96), respectively. Predictive phenotype panel of GDM, together with the risk factors of GDM, will provide novel perspectives for the early clinical warning and diagnosis of GDM.

A review of heat stress in chickens. Part I: Insights into physiology and gut health

Heat stress (HS) compromises the yield and quality of poultry products and endangers the sustainability of the poultry industry. Despite being homeothermic, chickens, especially fast-growing broiler lines, are particularly sensitive to HS due to the phylogenetic absence of sweat glands, along with the artificial selection-caused increase in metabolic rates and limited development of cardiovascular and respiratory systems. Clinical signs and consequences of HS are multifaceted and include alterations in behavior (e.g., lethargy, decreased feed intake, and panting), metabolism (e.g., catabolic state, fat accumulation, and reduced skeletal muscle accretion), general homeostasis (e.g., alkalosis, hormonal imbalance, immunodeficiency, inflammation, and oxidative stress), and gastrointestinal tract function (e.g., digestive and absorptive disorders, enteritis, paracellular barrier failure, and dysbiosis). Poultry scientists and companies have made great efforts to develop effective solutions to counteract the detrimental effects of HS on health and performance of chickens. Feeding and nutrition have been shown to play a key role in combating HS in chicken husbandry. Nutritional strategies that enhance protein and energy utilization as well as dietary interventions intended to restore intestinal eubiosis are of increasing interest because of the marked effects of HS on feed intake, nutrient metabolism, and gut health. Hence, the present review series, divided into Part I and Part II, seeks to synthesize information on the effects of HS on physiology, gut health, and performance of chickens, with emphasis on potential solutions adopted in broiler chicken nutrition to alleviate these effects. Part I provides introductory knowledge on HS physiology to make good use of the nutritional themes covered by Part II.

Fecal microbiota and their association with heat stress in Bos taurus

Background

Humans have been influencing climate changes by burning fossil fuels, farming livestock, and cutting down rainforests, which has led to global temperature rise. This problem of global warming affects animals by causing heat stress, which negatively affects their health, biological functions, and reproduction. On the molecular level, it has been proved that heat stress changes the expression level of genes and therefore causes changes in proteome and metabolome. The importance of a microbiome in many studies showed that it is considered as individuals’ “second genome”. Physiological changes caused by heat stress may impact the microbiome composition.

Results

In this study, we identified fecal microbiota associated with heat stress that was quantified by three metrics – rectal temperature, drooling, and respiratory scores represented by their Estimated Breeding Values. We analyzed the microbiota from 136 fecal samples of Chinese Holstein cows through a 16S rRNA gene sequencing approach. Statistical modeling was performed using a negative binomial regression. The analysis revealed the total number of 24 genera and 12 phyla associated with heat stress metrics. Rhizobium and Pseudobutyrivibrio turned out to be the most significant genera, while Acidobacteria and Gemmatimonadetes were the most significant phyla. Phylogenetic analysis revealed that three heat stress indicators quantify different metabolic ways of animals’ reaction to heat stress. Other studies already identified that those genera had significantly increased abundance in mice exposed to stressor-induced changes.

Conclusions

This study provides insights into the analysis of microbiome composition in cattle using heat stress measured as a continuous variable. The bacteria highly associated with heat stress were highlighted and can be used as biomarkers in further microbiological studies.

Heat stress impacts the multi-domain ruminal microbiota and some of the functional features independent of its effect on feed intake in lactating dairy cows

Background

Heat stress (HS) affects the ruminal microbiota and decreases the lactation performance of dairy cows. Because HS decreases feed intake, the results of previous studies were confounded by the effect of HS on feed intake. This study examined the direct effect of HS on the ruminal microbiota using lactating Holstein cows that were pair-fed and housed in environmental chambers in a 2 × 2 crossover design. The cows were pair-fed the same amount of identical total mixed ration to eliminate the effect of feed or feed intake. The composition and structure of the microbiota of prokaryotes, fungi, and protozoa were analyzed using metataxonomics and compared between two thermal conditions: pair-fed thermoneutrality (PFTN, thermal humidity index: 65.5) and HS (87.2 for daytime and 81.8 for nighttime).

Results

The HS conditions altered the structure of the prokaryotic microbiota and the protozoal microbiota, but not the fungal microbiota. Heat stress significantly increased the relative abundance of Bacteroidetes (primarily Gram-negative bacteria) while decreasing that of Firmicutes (primarily Gram-positive bacteria) and the Firmicutes-to-Bacteroidetes ratio. Some genera were exclusively found in the heat-stressed cows and thermal control cows. Some co-occurrence and mutual exclusion between some genera were also found exclusively for each thermal condition. Heat stress did not significantly affect the overall functional features predicted using the 16S rRNA gene sequences and ITS1 sequences, but some enzyme-coding genes altered their relative abundance in response to HS.

Conclusions

Overall, HS affected the prokaryotes, fungi, and protozoa of the ruminal microbiota in lactating Holstein cows to a different extent, but the effect on the structure of ruminal microbiota and functional profiles was limited when not confounded by the effect on feed intake. However, some genera and co-occurrence were exclusively found in the rumen of heat-stressed cows. These effects should be attributed to the direct effect of heat stress on the host metabolism, physiology, and behavior. Some of the “heat-stress resistant” microbes may be useful as potential probiotics for cows under heat stress.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00717-z.

Gut Microbiota and Serum Metabolite Potential Interactions in Growing Layer Hens Exposed to High-Ambient Temperature

Emerging evidence has revealed the dysbiosis of gut microbiota contributes to development of metabolic diseases in animals. However, the potential interaction between gut microbiota and host metabolism in growing hens under metabolic disorder induced by chronic heat exposure (CHE) remains inconclusive. The aim of our study was to examine the potential association among the cecal microbiota community, physiological indicators, and serum metabolite profiles in CHE hens. One hundred and eighty Hy-Line Brown hens were randomly allocated into three groups: thermoneutral control (TN), heat stress (HS), and pair-fed (PF). The experiment lasted for 5 weeks, with the first 2 weeks serving as the adaptation period. Results showed that the expression level of heat shock protein 70 (HSP70) in both serum and cecal tissues was significantly increased in the HS group. Serum parameters analysis also revealed that CHE caused physiological function damage and metabolic disorders. These results suggest the experiment was successful, inducing chronic heat stress. 16S rRNA sequencing analysis showed that the CHE can clearly induce dysbiosis of the gut microbial community reflected in the increment of the F/B ratio. Besides, serum untargeted metabolomics revealed the relative concentrations of 40 metabolites were significantly altered in the HS group compared with the TN group. Pathway analysis showed that these metabolites were mainly involving the increased proteolysis rather than lipolysis, and this tendency could be a specific metabolic adaptation of the poultry. The pair-feed experiment showed that the above changes induced by CHE were partly independent from the reduction of feed intake. Mantel correlation analysis between gut microorganisms and physiological indicators showed that the phylum Firmicutes and Euryarchaeota have a potential interaction with a serum lipid parameter. Random forest analysis showed that both genus Faecalibacterium and Methanobrevibacter were important predictors of the CHE-induced lipid metabolism disorder. Taken together, our findings may contribute to a better understanding of the metabolic mechanisms underlying the energy metabolism imbalance caused by the CHE and provide novel insights into the host-microbes interactions and its effects on the metabolic adaptation of hens under chronic heat exposure.

Use of Host Feeding Behavior and Gut Microbiome Data in Estimating Variance Components and Predicting Growth and Body Composition Traits in Swine

The purpose of this study was to investigate the use of feeding behavior in conjunction with gut microbiome sampled at two growth stages in predicting growth and body composition traits of finishing pigs. Six hundred and fifty-one purebred boars of three breeds: Duroc (DR), Landrace (LR), and Large White (LW), were studied. Feeding activities were recorded individually from 99 to 163 days of age. The 16S rRNA gene sequences were obtained from each pig at 123 ± 4 and 158 ± 4 days of age. When pigs reached market weight, body weight (BW), ultrasound backfat thickness (BF), ultrasound loin depth (LD), and ultrasound intramuscular fat (IMF) content were measured on live animals. Three models including feeding behavior (Model_FB), gut microbiota (Model_M), or both (Model_FB_M) as predictors, were investigated. Prediction accuracies were evaluated through cross-validation across genetic backgrounds using the leave-one-breed-out strategy and across rearing environments using the leave-one-room-out approach. The proportions of phenotypic variance of growth and body composition traits explained by feeding behavior ranged from 0.02 to 0.30, and from 0.20 to 0.52 when using gut microbiota composition. Overall prediction accuracy (averaged over traits and time points) of phenotypes was 0.24 and 0.33 for Model_FB, 0.27 and 0.19 for Model_M, and 0.40 and 0.35 for Model_FB_M for the across-breed and across-room scenarios, respectively. This study shows how feeding behavior and gut microbiota composition provide non-redundant information in predicting growth in swine.

Dietary Supplementation of Enzymatically Treated Artemisia annua L. Improves Lactation Performance, Alleviates Inflammatory Response of Sows Reared Under Heat Stress, and Promotes Gut Development in Preweaning Offspring

Artemisia annua L., which is known for its antimalarial compound artemisinin, has commonly been used for its anti-inflammatory and antibacterial functions. Enzymatically treating Artemisia annua L. can improve its bioavailability. The purpose of this study was to investigate the effects of dietary enzymatically treated Artemisia annua L. (EA) supplementation in late gestation and lactation diets on sow performance, serum hormone, inflammatory cytokines, and immunoglobulin level of heat-stressed sows. A total of 135 multiparous sows (Large White × Landrace) on day 85 of gestation were selected and randomly distributed into 3 groups with 45 replicates per group. The control group was reared under standard conditions (temperature: 27.12 ± 0.18°C, THI (temperature-humidity index): 70.90 ± 0.80) and fed with basal diet. The heat stress (HS) and HS + EA groups were raised in heat-stressed conditions (temperature: 30.11 ± 0.16°C, THI: 72.70 ± 0.60) and fed with basal diets supplemented with 0 or 1.0 g/kg EA, respectively. This trial lasted for 50 consecutive days until day 21 of lactation. Compared with the control group, HS increased the concentrations of serum endotoxin and heat shock protein 70 (HSP-70), and inflammatory cytokines in serum, colostrum, and 14 day milk of sows. Meanwhile, the EA supplementation decreased levels of serum endotoxin, HSP-70, and inflammatory cytokines in both sows and offspring and increased serum triiodothyronine (T₃) level and average daily feed intake (ADFI) of sows. In addition, EA significantly improved average daily gain (ADG) and altered intestinal morphology with an increased villus height in the duodenum and ileum of piglets. Collectively, EA supplementation at 1.0 g/kg in late gestation and lactation diets alleviated the adverse effects of HS, which were reflected by enhancing ADFI and decreasing endotoxin as well as inflammatory cytokine levels in the serum and colostrum of heat-stressed sows, while promoting ADG and gut development of their offspring.

Metabolic response of Lactobacillus acidophilus exposed to amoxicillin

Drug-induced diarrhea is a common adverse drug reaction, especially the one caused by the widespread use of antibiotics. The reduction of probiotics is one reason for intestinal disorders induced by an oral antibiotic. However, the intrinsic mechanism of drug-induced diarrhea is still unknown. In this study, we used metabolomics methods to explore the effects of the classic oral antibiotic, amoxicillin, on the growth and metabolism of Lactobacillus acidophilus, while scanning electron microscopy (SEM) and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays were employed to evaluate changes in cell activity and morphology. The results showed that cell viability gradually decreased, while the degree of cell wall rupture increased, with increasing amoxicillin concentrations. A non-targeted metabolomics analysis identified 13 potential biomarkers associated with 9 metabolic pathways. The data showed that arginine and proline metabolism, nicotinate and nicotinamide metabolism, pyrimidine metabolism, glycine, serine and threonine metabolism, beta-alanine metabolism, glycerolipid metabolism, tryptophan metabolism, steroid hormone biosynthesis, and histidine metabolism may be involved in the different effects exerted by amoxicillin on L. acidophilus. This study provides potential targets for screening probiotics regulators and lays a theoretical foundation for the elucidation of their mechanisms.

Metabolic Responses of Dietary Fiber during Heat Stress: Effects on Reproductive Performance and Stress Level of Gestating Sows

Heat stress is an important issue, and the addition of fiber to the diet is an option in modifying intestinal health. This study evaluated the effect of acid detergent fiber (ADF) levels on reproductive performance, intestinal integrity, and metabolism of gestating sows, and its carry-over effect on the lactation period during heat stress. The diets included 4.3% (Low fiber; LF), 5.4% (Medium fiber; MF), and 6.5% (High fiber; HF) ADF. Sows fed the HF diet showed a lower respiratory rate, hair cortisol concentration, and farrowing duration compared with the LF treatment. The HF diet increased the pyruvate, citrate cycle, glyoxylate, dicarboxylate, and thiamine metabolism compared with the MF. The concentration of acetate and total short-chain fatty acids were increased in the sows fed the HF diet. The gene expression of glucose transporter 3 and glucose transporter 4 was increased in the HF treatment. The gene expression of heat shock protein 70 was decreased in the HF treatment. The HF diet during gestation increased feed intake, constipation index, piglet weight, and litter weight compared with the LF. Sows in the LF treatment showed the greatest digestibility of crude protein and the lowest digestibility of ADF. In conclusion, a 6.5% ADF level is recommended for gestating sows during heat stress.

Heat Stress Affects Faecal Microbial and Metabolic Alterations of Rabbits

Heat stress can impair the rabbit immune system, induce oxidative stress, and cause many complications. These diseases are characterized by metabolic disorders, but the underlying mechanism is unknown. As a result, the current research determines the effects of HS on intestinal microorganisms in rabbits and the metabolic pathway disorders caused by HS. Twelve rabbits were randomly assigned to one of two groups: CON (22–24°C) and HS (30°C–32°C). Both the groups were treated for 15 days. Blood and fecal samples were collected on day 15. Serum immune oxidation indices were determined using a commercial ELISA kit, and the microbiome of rabbit feces was studied using 16S rRNA gene sequencing. Non-targeted metabolomics was analyzed using ultra-high-performance liquid chromatography-mass spectrometry (UHPC MS/MS). The findings revealed that HS significantly increased IgG and T-AOC levels in serum, whereas it decreased TNF-α and IL-10. NMDS analysis revealed a substantial difference in bacterial community composition between HS and CON groups. At the phylum level, the abundance of Firmicutes, Protobacteria, and Verrucomicrobiota was significantly higher in the HS group, whereas the abundance of Bacteriodota was reduced in the CON group. V9D2013 group, Haloplasma, Comamonas, Clostridium sensu stricto 1, Ruminiclostridium, Syntrophus Lutispora, at the genus level Syntrophorhabdus, Paeniclostridium, Clostridium sensu stricto 6, Candidatus Caldatribacterium, Spirochaeta Synergistaceae, Syner-01, [Eubacterium] xylanophilum group, Cellulosilyticum, ADurb.Bin120, and Devosia were significantly upregulated in the HS group. The metabolism of the HS group was considerably upregulated compared with the metabolism of the CON group, according to principal component analysis (PCA) and least-squares discriminant analysis (PLS-DA). HS increased the concentrations of 4-pyridoxic acid, kynurenine, 20-OH-leukotriene B4, and dopamine and decreased the concentration of pyridoxal. In the rabbit gut, these compounds primarily impact the metabolic pathways of vitamin B6, tryptophan, neutrophil activation, and prolactin. 4-Pyridoxic acid, pyridoxal, kynurenine, 20-OH-leukotriene B4, and dopamine are essential inflammatory response markers and oxidative stress.

Modulation of Fecal Metabolites by Heat Stress and Diet, and Their Association with Inflammation and Leaky Gut Markers in Dairy Cows

The analysis of fecal metabolite profiles could provide novel insights into the mechanisms underlying animal responses to environmental stressors and diet. We aimed to evaluate the effects of a 14-day heat stress period and of dietary mineral and vitamin supplementation under heat stress on fecal metabolite profiles and to investigate their associations with physiological markers of heat stress, leaky gut, and inflammation in lactating dairy cows. Twelve multiparous Holstein cows (42.2 ± 5.6 kg milk/d; 83.4 ± 27.1 DIM) were enrolled in an experiment in a split-plot design. The main plot was the level of dietary vitamin E and Se, as follows: (1) low (L-ESe; 20 IU/kg vitamin E, 0.3 ppm Se) or (2) high (H-ESe 200 IU/kg vitamin E, 1.2 ppm Se). Within each plot, six cows were randomly assigned to either (1) heat stress (HS; Total Humidity Index (THI): 82), (2) pair-feeding in thermoneutrality (TNPF; THI = 64), or (3) HS with vitamin D₃ and Ca supplementation (HS+DCa; 1820 IU/kg and 1.5% Ca; THI: 82) in a replicated 3 × 3 Latin square design with 14-day periods and 7-day washouts. The concentrations of 94 metabolites were determined in fecal samples, including amino acids, fatty acids, biogenic amines, and vitamins. Relative to the L-ESe group, the H-ESe group increased α-tocopherol by threefold, whereas δ-tocopherol was decreased by 78% (P_FDR < 0.01). Nevertheless, correlation analysis between α-tocopherol and all the others fecal metabolites or physiological heat stress measures did not show significant associations. No interactions between main plot and treatments were observed. Relative to TNPF, HS increased plasma tumor necrosis factor-alpha (TNF-α), plasma lipopolysaccharide-binding protein (LBP), milk somatic cell counts (SCC), respiratory rates, rectal temperatures, fecal tridecylic and myristic acids, vitamin B₇, and retinol, whereas it decreased fecal amino acids such as histidine, methyl histidine, acetyl ornithine, and arginine (P_FDR < 0.05). In contrast, HS+DCa increased fecal methyl histidine concentrations and reduced milk SCC, plasma TNF-α, and LBP, as well as rectal temperatures. Discriminant analysis revealed fecal histidine, taurine, acetyl ornithine, arginine, β-alanine, ornithine, butyric + iso-butyric acid, plasma non-esterified fatty acids, TNF-α, LBP, C-reactive protein, and milk SCC were predictive of HS. Several metabolites were predictive of HS+DCa, although only tryptophan was discriminant relative to HS. In conclusion, both heat stress and the supplementation of vitamin D₃ and Ca can influence the fecal metabolome of dairy cows experiencing heat stress, independently of dietary levels of vitamin E and Se. Our results suggest that some fecal metabolites are well associated with physiological measures of heat stress and may thus provide insights into the gut-level changes taking place under heat stress in dairy cows.

Alterations in intestinal microbiota composition coincide with impaired intestinal morphology and dysfunctional ileal immune response in growing-finishing pigs under constant chronic heat stress

Background

Previous studies had shown that short-term acute heat stress (HS) affected the host’s metabolism and intestinal microbiota independent of feed intake (FI) reduction, and long-term calorie restriction caused intestinal morphological injuries and gut microbial alterations. However, research on the effects of constant chronic HS on intestinal microbial composition and the roles of FI reduction played in is limited. This study aimed to investigate the effects of 7-day constant chronic HS on the composition of intestinal microbes in growing-finishing pigs, and its relationship with pigs’ performance, intestinal morphology, and ileal immune response. Twenty-four growing-finishing pigs (Duroc × Large White × Landrace, 30 ± 1 kg body weight) were randomly assigned to three treatments (n = 8), 1) thermal neutral (TN) conditions (25 ± 1 °C) with ad libitum FI, 2) HS conditions (35 ± 1 °C) with ad libitum FI, 3) pair-fed (PF) with HS under TN conditions to discriminate the confounding effects of dissimilar FI, and the FI was the previous day’s average FI of HS. The small intestinal segments (duodenum, jejunum, and ileum) and feces were collected on d 8.

Results

Results indicated that HS drastically declined (P < 0.05) average daily gain (ADG) and average daily feed intake (ADFI) (about 61%) in comparison with TN, and caused hyperpyrexia, meanwhile PF caused hypothermia. Morphological observation by light and electron microscopes showed that both HS and PF treatment decreased (P < 0.05) the villus and microvillus height compared with TN. Additionally, HS increased (P < 0.05) protein expression of heat shock protein 70 in the duodenum, jejunum, and ileum. Furthermore, the expression of tight junction protein zonula occluden-1 (ZO-1) in the duodenum and ileum, and Occludin in the ileum were enhanced (P < 0.05) compared with TN and PF. Moreover, HS significantly enhanced (P < 0.05) the mRNA relative expression of inflammatory cytokines (TLR-2, TLR-4, and tumor necrosis factor-α (TNF-α), IL-6, IL-8, PG1–5, β-defensin 2 (pBD-2)), mucins (mucin-1 and mucin-2) and P65 protein level in the ileal mucosa tissue. Intestinal microbiota analysis by 16S rRNA sequencing showed lower (P < 0.10) α diversity in both HS and PF, and a separated cluster of β diversity among groups. Compared with TN, HS but not PF mainly reduced (FDR < 0.05) Bacteroidetes (phylum), Bacteroidia (class) and elevated the proportions of Proteobacteria (phylum, FDR < 0.05), Bacillales (order, FDR < 0.05), Planococcaceae (family, FDR < 0.05), Kurthia (genus, FDR < 0.05), Streptococcaceae (family, FDR < 0.10) and Streptococcus (genus, FDR < 0.10). Notably, Lactobacillales (order) was decreased (FDR < 0.05) by PF alone. Furthermore, the Spearman correlation analysis indicated that the microbes prevalent in HS were positively (P < 0.05) associated with intestinal morphological injuries indicators and ileal immune response parameters, and the microbes reduced in HS were negatively (P < 0.05) with the performance data.

Conclusions

Intestinal morphological injuries and ileal immune response caused by constant chronic HS independent of FI showed close connections with alterations in intestinal microbiota in growing-finishing pigs.

Comparative effects of different enzymatic hydrolysates of konjac glucomannan on gut flora and constipation rats

This study aimed to compare the effects of different hydrolysates (named GKOS and MKOS) on constipated rats, which were degraded to obtain from konjac glucomannan by β-glucanase and β-mannanase, respectively....

Microbiota-gut-brain axis and nutritional strategy under heat stress

Heat stress is a very universal stress event in recent years. Various lines of evidence in the past literatures indicate that gut microbiota composition is susceptible to variable temperature. A varied microbiota is necessary for optimal regulation of host signaling pathways and disrupting microbiota-host homeostasis that induces disease pathology. The microbiota–gut–brain axis involves an interactive mode of communication between the microbes colonizing the gut and brain function. This review summarizes the effects of heat stress on intestinal function and microbiota–gut–brain axis. Heat stress negatively affects intestinal immunity and barrier functions. Microbiota-gut-brain axis is involved in the homeostasis of the gut microbiota, at the same time, heat stress affects the metabolites of microbiota which could alter the function of microbiota–gut–brain axis. We aim to bridge the evidence that the microbiota is adapted to survive and thrive in an extreme environment. Additionally, nutritional strategies for alleviating intestinal heat stress are introduced.

Early social contact alters the community structure and functions of the faecal microbiome in suckling-growing piglets

Social contact during suckling, in an enriched social environment, can reduce the aggressive behaviours of piglets during regrouping at weaning, and improve their production performance and welfare. The aim of this study was to determine the possible impact of suckling social contact on gut microbes. We performed 16S rRNA sequencing to measure the faecal microbial structure and function in piglets experiencing social contact. Eighteen-litter piglets were allocated to two treatments: an early continuous social contact (CSC) group where piglets from adjacent pens shared a mutual pen starting at 14 days postpartum and a control (CON) group where piglets had no contact with individuals from adjacent pens during the suckling period. The piglets were regrouped at 36 days of age. The litter weights at 35 and 63 days of age were measured. Faecal samples were randomly collected at 16, 35, 42, and 63 days of age and faecal DNA was determined. The results showed that the litter weight of piglets in the CSC group was significantly decreased at 63 days compared with the CON group. Continuous social contact also significantly decreased the microbial richness at 16 and 35 days of age (P < 0.05). Firmicutes was the most abundant bacterial phylum in both groups at all detected time-points and the abundance increased with social contact. At the genus level, Lactobacillus was the most abundant bacterium after weaning and the abundance increased in the piglets with social contact. Compared with the faecal microbiota of control piglets, a total of 22 genera at 16 days, 20 genera at 35 days, 12 genera at 42 days, and 27 genera at 63 days in the faeces of CSC piglets were observed to be significantly different in abundance (linear discriminant analysis score > 3, P < 0.05). Furthermore, functional analysis of the microbial composition showed that the changes induced by early CSC mainly altered the relative abundance of metabolic and related pathways. The social contact notably had an effect on the abundance of microbial pathways for amino acid and carbohydrate metabolism. In conclusion, CSC changed the microbial composition in the faeces of piglets, which might have a negative effect on nutrient metabolism for the suckling-growing piglets. Our study provided new insight into the influence of social contact on the suckling-growing piglets.

Selenium-enriched Bifidobacterium longum DD98 attenuates irinotecan-induced intestinal and hepatic toxicity in vitro and in vivo

Irinotecan (CPT-11) is a camptothecin chemotherapy drug largely used in treating cancers. However, its strong adverse effects, such as gastrointestinal and hepatic toxicities, tend to reduce the patients' life qualities and to limit the clinical use of CPT-11. The protective roles of selenium (Se) and probiotics against CPT-11-induced toxicity have been widely reported. However, the application of Se-enriched probiotics in the adjuvant therapy of CPT-11 has not been well explored. The purpose of this study is to evaluate the in-vitro and in-vivo effects of Se-enriched Bifidobacterium longum DD98 (Se-B. longum DD98) as a chemotherapy preventive agent on alleviating intestinal and hepatic toxicities induced by CPT-11 chemotherapy. The results showed that Se-B. longum DD98 positively regulated the aberrant cell viability and oxidative stress induced by CPT-11 both in human normal liver (L-02) and rat small intestinal epithelial (IEC-6) cell lines. In vivo experiment revealed that Se-B. longum DD98 significantly attenuated intestinal and hepatic toxicities by ameliorating symptoms such as body weight loss and diarrhea, and by improving the biochemical indicators of hepatotoxicity and oxidative stress. Furthermore, we discovered that the protective effects of Se-B. longum DD98 based largely upon decreasing the pro-inflammatory cytokines IL-1β and IL-18 and enhancing the expression of tight-junction proteins occludin and ZO-1, as well as restoring the composition and diversity of gut microbiota. Results suggested that Se-B. longum DD98 effectively protected livers and intestines against the CPT-11-induced damages, and therefore, could be considered as a promising adjuvant therapeutic agent with CPT-11 for the cancer treatment.

Heat Stress Alters the Intestinal Microbiota and Metabolomic Profiles in Mice

Background

Heat stress has negative effects on the intestinal health of humans and animals. However, the impact of heat stress on intestinal microbial and metabolic changes remains elusive. Here, we investigated the cecal microbial and metabolic profiles in mice in response to heat stress.

Methods

The mouse heat stress model was constructed by simulating a high-temperature environment. Twenty mice were randomly assigned to two groups, the control group (CON, 25°C) and the heat treatment group (HS, 40°C from 13:00 to 15:00 every day for 7 days). Serum and cecal contents were collected from the mice for serum biochemical analysis, 16S rRNA high-throughput sequencing, and non-targeted metabolomics.

Results

Both core body temperature and water intake were significantly increased in the HS group. Serum biochemical indicators were also affected, including significantly increased triglyceride and decreased low-density lipoprotein in the heat stress group. The composition and structure of intestinal microbiota were remarkably altered in the HS group. At the species level, the relative abundance of Candidatus Arthromitus sp. SFB-mouse-Japan and Lactobacillus murinus significantly reduced, while that of Lachnospiraceae bacterium 3-1 obviously increased after HS. Metabolomic analysis of the cecal contents clearly distinguished metabolite changes between the groups. The significantly different metabolites identified were mainly involved in the fatty acid synthesis, purine metabolism, fatty acid metabolism, cyanoamino acid metabolism, glyceride metabolism, and plasmalogen synthesis.

Conclusion

In summary, high temperature disrupted the homeostatic balance of the intestinal microbiota in mice and also induced significant alterations in intestinal metabolites. This study provides a basis for treating intestinal disorders caused by elevated temperature in humans and animals and can further formulate nutritional countermeasures to reduce heat stress-induced damage.

High ambient temperature exposure during late gestation disrupts glycolipid metabolism and hepatic mitochondrial function tightly related to gut microbial dysbiosis in pregnant mice

As global warming intensifies, emerging evidence has demonstrated high ambient temperature during pregnancy negatively affects maternal physiology with compromised pregnant outcomes; however, little is known about the roles of gut microbiota and its underlying mechanisms in this process. Here, for the first time, we explored the potential mechanisms of gut microbiota involved in the disrupted glycolipid metabolism via hepatic mitochondrial function. Our results indicate heat stress (HS) reduces fat and protein contents and serum levels of insulin and triglyceride (TG), while increases that of non-esterified fatty acid (NEFA), β-hydroxybutyric acid (B-HBA), creatinine and blood urea nitrogen (BUN) (P < 0.05). Additionally, HS downregulates both mitochondrial genes (mtDNA) and nuclear encoding mitochondrial functional genes with increasing serum levels of malondialdehyde (MDA) and 8-hydroxydeoxyguanosine (8-OHdG) (P < 0.05). Regarding microbial response, HS boosts serum levels of lipopolysaccharide (LPS) (P < 0.05) and alters β-diversity (ANOSIM, P < 0.01), increasing the proportions of Escherichia-Shigella, Acinetobacter and Klebsiella (q < 0.05), while reducing that of Ruminiclostridium, Blautia, Lachnospiraceae_NK4A136_group, Clostridium VadinBB60 and Muribaculaceae (q < 0.05). PICRUSt analysis predicts that HS upregulates 11 KEGG pathways, mainly including bile secretion and bacterial invasion of epithelial cells. The collective results suggest that microbial dysbiosis due to late gestational HS has strong associations with damaged hepatic mitochondrial function and disrupted metabolic profiles.

Thermoregulatory and physiological responses of nonpregnant, mid-gestation, and late-gestation sows exposed to incrementally increasing dry bulb temperature

Gestating sows may be more susceptible to increasing dry bulb temperatures (TDB) due to greater metabolic heat production and increased body mass, especially as gestation advances. However, there are few studies on the thermoregulatory and physiological responses of sows at differing gestation stages exposed to gradually increasing temperatures. The study objective was to determine the thermoregulatory and physiological responses of nonpregnant (n = 12; parity 3.27 ± 0.86), mid-gestation (59.7 ± 9.6 d pregnant, n = 12; parity 3.25 ± 0.83), and late-gestation (99.0 ± 4.8 d pregnant, n = 12; parity 3.33 ± 0.75) sows exposed to increasing TDB. Prior to the experiment (5.0 ± 0.7 d), jugular catheters were placed in all sows. During the experiment, the TDB was increased incrementally by 2.45 ± 0.43 °C every 60 min from 19.84 ± 2.15 to 35.54 ± 0.43 °C over 400 min, and relative humidity was recorded at 40.49 ± 18.57%. Respiration rate (RR), heart rate (HR), skin temperature, and vaginal temperature were measured, and blood samples were obtained via the jugular catheter every 20 min. Data were analyzed using PROC MIXED in SAS 9.4. RR increased at a lower TDB (P < 0.01) in late-gestation sows compared with mid-gestation and nonpregnant sows, but no differences were detected between mid-gestation and nonpregnant sows. Overall, late-gestation sows had greater RR (P < 0.01; 23 ± 2 breaths per min [brpm]) compared with mid-gestation (16 ± 2 brpm) and nonpregnant (15 ± 2 brpm) sows. Late-gestation sows had an overall greater HR (P < 0.01; 84 ± 5 beats per min [bpm]) than mid-gestation (76 ± 5 bpm) and nonpregnant (69 ± 5 bpm) sows. Late-gestation sows had overall reduced bicarbonate and total carbon dioxide levels (P = 0.02; 23.89 ± 1.97 and 25.41 ± 2.07 mmol/L, respectively) compared with mid-gestation (27.03 ± 1.97 and 28.58 ± 2.07 mmol/L, respectively) and nonpregnant (26.08 ± 1.97 and 27.58 ± 2.07 mmol/L, respectively) sows. Moreover, late-gestation sows had overall greater nitric oxide levels (P < 0.01; 248.82 ± 34.54 µM) compared with mid-gestation (110.47 ± 34.54 µM) and nonpregnant (41.55 ± 34.54 µM) sows. In summary, late-gestation sows appear to be more sensitive to increasing TDB as indicated by thermoregulatory and physiological responses when compared with mid-gestation or nonpregnant sows. The results from this study provide valuable information regarding thermoregulatory thresholds of sows at differing gestation stages.

Potential Use of Gut Microbiota Composition as a Biomarker of Heat Stress in Monogastric Species: A Review

Simple Summary

Heat stress is a significant environmental challenge faced by food animal production worldwide because of its adverse effects on animal performance and productivity. Trillions of microorganisms living in the gut are essential for host health by participating in various digestive, immune, and metabolic activities. At the same time, they are known to be sensitive to changes in the surrounding environment. The present review summarizes current research progress of how the gut microbial community responds to elevated ambient heat in monogastric animal species and discusses the use of the gut microbiota composition as a potential indicator for heat stress.

Abstract

Heat stress is a current challenge for livestock production, and its impact could dramatically increase if global temperatures continue to climb. Exposure of agricultural animals to high ambient temperatures and humidity would lead to substantial economic losses because it compromises animal performance, productivity, health, and welfare. The gut microbiota plays essential roles in nutrient absorption, energy balance, and immune defenses through profound symbiotic interactions with the host. The homeostasis of those diverse gut microorganisms is critical for the host’s overall health and welfare status and also is sensitive to environmental stressors, like heat stress, reflected in altered composition and functionality. This article aims to summarize the research progress on the interactions between heat stress and gut microbiome and discuss the potential use of the gut microbiota composition as a biomarker of heat stress in monogastric animal species. A comprehensive understanding of the gut microbiota’s role in responding to or regulating physiological activities induced by heat stress would contribute to developing mitigation strategies.

Methyl-Donor Micronutrient for Gestating Sows: Effects on Gut Microbiota and Metabolome in Offspring Piglets

This study aimed to investigate the effects of maternal methyl-donor micronutrient supplementation during gestation on gut microbiota and the fecal metabolic profile in offspring piglets. Forty-three Duroc × Erhualian gilts were assigned to two dietary groups during gestation: control diet (CON) and CON diet supplemented with MET (folic acid, methionine, choline, vitamin B6, and vitamin B12). The body weights of offspring piglets were recorded at birth and weaning. Besides this, fresh fecal samples of offspring piglets were collected at 7, 14, and 21 days. The gut microbiota composition, metabolic profile, and short-chain fatty acid (SCFA) profiles in the fecal samples were determined using 16S rDNA sequencing, liquid chromatography-mass spectrometry metabolomics, and gas chromatography methods, respectively. The results showed that maternal methyl-donor micronutrient supplementation increased the microbiota diversity and uniformity in feces of offspring piglets as indicated by increased Shannon and Simpson indices at 7 days, and greater Simpson, ACE, Chao1 and observed species indices at 21 days. Specifically, at the phylum level, the relative abundance of Firmicutes and the Firmicutes to Bacteroidetes ratio were elevated by maternal treatment. At the genus level, the relative abundance of SCFA-producing Dialister, Megasphaera, and Turicibacter, and lactate-producing Sharpea as well as Akkermansia, Weissella, and Pediococcus were increased in the MET group. The metabolic analyses show that maternal methyl-donor micronutrient addition increased the concentrations of individual and total SCFAs of 21-day piglets and increased metabolism mainly involving amino acids, pyrimidine, and purine biosynthesis. Collectively, maternal methyl-donor micronutrient addition altered gut microbiota and the fecal metabolic profile, resulting in an improved weaning weight of offspring piglets.

Effects of recovery from short-term heat stress exposure on feed intake, plasma amino acid profiles, and metabolites in growing pigs

Heat stress (HS) damages health and decreases performance variables in pigs, and if severe enough, causes mortality. However, metabolic changes under HS and recovery following HS are poorly understood. Therefore, this study was aimed to expose the essential mechanisms by which growing pigs respond to HS and the temporal pattern of plasma concentrations (PC) of amino acids (AAs) and metabolites. Crossbred male growing pigs were penned separately and allowed to adapt to thermal-neutral (TN) conditions (20°C and 80% relative humidity; TN[-1D]). On the first day, all pigs were exposed to HS for 24 h (36°C and 60% relative humidity), then to TN conditions for 5 days (TN[2D] to TN[5D]). All pigs had ad libitum access to water and 3 kg feed twice daily. Rectal temperature (RT) and feed intake (FI) were determined daily. HS pigs had higher RT (40.72°C) and lower (50%) FI than TN(-1D) pigs (p < 0.01). The PC of indispensable (threonine, valine, and methionine) and dispensable (cysteine and tyrosine) AAs were higher (p < 0.05) in HS than TN(-1D) pigs and remained increased during recovery time. Nonprotein α-aminobutyric acid and β-alanine concentrations were higher (p < 0.05) in HS than TN(-1D) pigs. The metabolite concentration of creatinine was higher (p < 0.01) under HS treatment than other treatments, but that of alanine and leucine remained increased (p < 0.05) through 5 d of recovery. In summary, some major differences were found in plasma AA profiles and metabolites between HS- and TN-condition pigs. This indicates that the HS pigs were forced to alter their metabolism, and these results provide information about mechanisms of acute HS responses relative to the recovery time.

Effects of Heat Stress on Gut Microbiome in Rats

Gut microbiome, as the largest and most important micro-ecosystem, plays a critical role in health. The purpose of this study was to evaluate whether heat stress modulates the composition and diversity of the gut microbiome in rats. The heat stress model was prepared in rats with the heating temperature maintained at 35–38°C. Cecum contents were collected after heat stress for 3 h and days 1, 3 and 7. Total DNA was extracted for 16 S rRNA sequencing and analysis of intestinal microbiome composition and diversity. The study showed that the composition of the intestinal microbiome of heat stress group was changed. And the heat stress modulated key phylotypes of gut microbiota at the level of phylum and genus. In particular, the genus of Lactobacillus and Bacteroides were significantly reduced, whereas the Oscillospira and Clostridium were increased by heat stress. Meanwhile, the rats under the heat stress encountered the change in carbohydrate metabolism, amino acid metabolism, and membrane transport to defense against stress. Taken together, the composition and structure of gut microbiome were affected by heat stress and some key phylotypes were also significantly altered. We conclude that the heat stress could impact multiple biological functions, via altering the gut microbiome.

Saccharomyces cerevisiae boulardii CNCM I-1079 supplementation in finishing male pigs helps to cope with heat stress through feeding behaviour and gut microbiota modulation

Pigs subjected to heat stress (HS) decrease their feed intake and growth. The objectives of the experiment were to determine the effects of live yeast (LY) supplementation (Saccharomyces cerevisiae var boulardii CNCM I-1079) on feeding behaviour, energy metabolism and faecal microbiota composition of finishing boars (n 10) housed in a respiration chamber at thermoneutrality (7 d at 22°C) or during HS (seven plus six days at 28°C). Dietary LY supplementation increased DM intake (P = 0·01) whatever the ambient temperature, whereas HS decreased feed intake whatever the dietary supplementation (P = 0·01). Dietary LY supplementation increased the number of meals (P = 0·02). Energy retention was higher with dietary LY supplementation (P < 0·01) but decreased during HS (P < 0·01). The skin temperature of the supplemented pigs was lower at thermoneutrality and increased during HS to a lesser extent than that of non-supplemented pigs (P < 0·01). Faecal microbiota composition was determined using 16S rRNA gene sequencing. Treponema, Christensenellaceae R-7, Ruminococcaceae UCG-002, Rikenellaceae RC9, Clostridium sensu stricto 1 and Romboutsia genera and some bacteria belonging to Alloprevotella, Oxalobacter and Anaeroplasma genera were more abundant under HS. LY supplementation attenuated HS effects on Romboutsia abundance, while decreasing the abundance of some bacteria from Ruminoccocus, Coprococcus, Peptococcus and Oxalobacter genera and increasing the abundance of beneficial bacteria from Lactococcus and Subdoligranulum genera. Our results suggest that higher level of the keystone species Ruminococcus bromii at thermoneutrality may be one of the causes for higher energy retention observed under subsequent HS.

Oral administration of Moringa oleifera leaf powder relieves oxidative stress, modulates mucosal immune response and cecal microbiota after exposure to heat stress in New Zealand White rabbits

Background

Heat stress (HS) disrupts the gut barrier allowing the uptake of lipopolysaccharide (LPS) and leads to an inflammatory response and changes in gut microbiota composition. Moringa oleifera leaf powder (MOLP) has been proposed to combat HS, yet its alleviate role is currently under investigation. The current study investigated the effects of chronic HS and MOLP supplementation on changes in redox status and immune response of cecal mucosa along with alteration in cecal microbiota.

Methods

A total of 21 young New Zealand White (NZW) rabbits (male) about 32 weeks old (mean body weight of 3318 ± 171 g) reared on a commercial pelleted diet were employed; divided into three groups (n = 7): control (CON, 25 °C), heat stress (HS, 35 °C for 7 h daily), and HS supplemented orally with MOLP (HSM, 35 °C) at 200 mg/kg body weight per day for 4 weeks.

Results

The results demonstrated that MOLP supplementation increased organ index of cecal tissue compared with the HS group (P > 0.05). Levels of malonaldehyde (MDA) and activity of superoxide dismutase (SOD) as well as lactate dehydrogenase (LDH) were reduced in the cecal mucosa of the HSM group compared with the HS group. MOLP downregulated the contents of cecal mucosa LPS, several inflammatory markers (TNF-α/IL-1α/IL-1β), and myeloperoxidase (MPO) in the HSM group (P < 0.05). Secretory immunoglobulin A (SIgA) was increased in the HSM group compared with the HS group (P < 0.05). The transcriptome of cecal mucosa showed that MOLP reduced gene expression relative to several immune factors, including IL-10, IFNG, and RLA, whereas both HS and MOLP increased the gene expression of fat digestion and absorption pathway, including APOA1, FABP1, FABP2, MTTP, and LOC100344166, compared to the CON group (P < 0.001). At the phylum level, the relative abundance of Proteobacteria was increased by HS, while Actinobacteria was significantly increased by HSM compared to other groups (P < 0.05). At genus level, Papillibacter was higher in abundance in HSM groups compared to CON and HS groups (P < 0.05). Higher butyrate concentrations were observed in the HSM group than HS and CON groups (P < 0.05).

Conclusion

In conclusion, HS in growing rabbits resulted in alteration of cecal microbiota at phyla level as well as increased oxidative stress and expression of mucosal inflammatory genes. Whereas, oral MOLP supplementation elevated the relative weight of cecum, affected their immunological and cecal micro-ecosystem function by improving antioxidant status and down-regulating mucosal tissue inflammatory response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00586-y.

Heat stress on microbiota composition, barrier integrity, and nutrient transport in gut, production performance, and its amelioration in farm animals

Livestock species experience several stresses, particularly weaning, transportation, overproduction, crowding, temperature, and diseases in their life. Heat stress (HS) is one of the most stressors, which is encountered in livestock production systems throughout the world, especially in the tropical regions and is likely to be intensified due to global rise in environmental temperature. The gut has emerged as one of the major target organs affected by HS. The alpha- and beta-diversity of gut microbiota composition are altered due to heat exposure to animals with greater colonization of pathogenic microbiota groups. HS also induces several changes in the gut including damages of microstructures of the mucosal epithelia, increased oxidative insults, reduced immunity, and increased permeability of the gut to toxins and pathogens. Vulnerability of the intestinal barrier integrity leads to invasion of pathogenic microbes and translocation of antigens to the blood circulations, which ultimately may cause systematic inflammations and immune responses. Moreover, digestion of nutrients in the guts may be impaired due to reduced enzymatic activity in the digesta, reduced surface areas for absorption and injury to the mucosal structure and altered expressions of the nutrient transport proteins and genes. The systematic hormonal changes due to HS along with alterations in immune and inflammatory responses often cause reduced feed intake and production performance in livestock and poultry. The altered microbiome likely orchestrates to the hosts for various relevant biological phenomena occurring in the body, but the exact mechanisms how functional communications occur between the microbiota and HS responses are yet to be elucidated. This review aims to discuss the effects of HS on microbiota composition, mucosal structure, oxidant-antioxidant balance mechanism, immunity, and barrier integrity in the gut, and production performance of farm animals along with the dietary ameliorations of HS. Also, this review attempts to explain the mechanisms how these biological responses are affected by HS.