Intestinal integrity, endotoxin transport and detoxification in pigs divergently selected for residual feed intake

Assessment of a 50:50 mixture of two Bacillus subtilis strains as growth promoters for finishing pigs: productivity improvement and noxious gas reduction

In this study, we aimed to assess the potential of a 50:50 mixture of two Bacillus subtilis strains in improving the productivity and health of finishing pigs and reducing noxious gases in their feces. These strains were found to abundantly secrete surfactin which has been shown to alleviate the effects of lipopolysaccharides in vitro. For the 10-wk experiment, 200 finishing pigs ([Landrace × Yorkshire] × Duroc) with an average body weight of 54.15 ± 1.70 kg were divided into four groups. Each group was fed with a basal diet supplemented with an equal amount of spores from the two B. subtilis strains at different levels: control group, no addition; treatment group 1, 0.5 × 109; treatment group 2, 1.0 × 109; treatment group 3, 1.5 × 109 cfu·kg-1 addition. During the 10-wk feeding period, dietary supplementation of 0.5 × 109, 1.0 × 109, and 1.5 × 109 cfu·kg-1 of the spore cells from these two strains resulted in a 0.9%, 1.9%, and 2.5% increase in body weight, respectively (linear P < 0.095). During the final 5 wk, the average daily gain (ADG) in weight was increased by the strains at amounts of 0.5 × 109, 1.0 × 109, and 1.5 × 109 cfu·kg-1 with a clear dosage effect (linear P < 0.05). However, neither the gain-to-feed ratio, the average daily feed intake, nor nutrient digestibility was affected by the supplementation. In blood, the endotoxin lipopolysaccharides, and two liver toxicity indicator enzymes; aspartate aminotransferase and lactate dehydrogenase were decreased (P < 0.05) in the 1.0 × 109 cfu·kg-1 spores-feeding group. Furthermore, four noxious gases were reduced by 8 to 20% in feces excreted by pigs fed with 1.5 × 109 cfu·kg-1 spores with a linear dosage effect (linear P < 0.001 to 0.05) during the final 5 wk. Our findings suggest that the mixture of B. subtilis strains may enhance the productivity of finishing pigs by reducing the risk of mild endotoxemia, rather than increasing digestibility or daily feed intake. Therefore, these Bacillus strains have the potential to act as growth promoters for pigs, leading to improved animal health and productivity. These results have significant implications for pig farmers seeking to optimize the health and growth of their animals.

Selenium Speciation Analysis Reveals Improved Antioxidant Status in Finisher Pigs Fed L-Selenomethionine, Alone or Combined with Sodium Selenite, and Vitamin E

Conditions associated with selenium (Se) and/or vitamin E (VitE) deficiency are still being reported in high-yielding pigs fed the recommended amounts. Here, the dietary effects of Se source (sodium selenite, NaSe, 0.40 or 0.65 mg Se/kg; L-selenomethionine, SeMet, 0.19 or 0.44 mg Se/kg; a NaSe-SeMet mixture, SeMix, 0.44-0.46 mg Se/kg) and VitE concentration (27, 50-53 or 101 mg/kg) on the antioxidant status of finisher pigs were compared with those in pigs fed non-Se-supplemented diets (0.08-0.09 mg Se/kg). Compared to NaSe-enriched diets, SeMet-supplemented diets resulted in significantly (p < 0.0018) higher plasma concentrations of total Se (14-27%) and selenospecies (GPx3, SelP, SeAlb; 7-83%), significantly increased the total Se accumulation in skeletal muscles, myocardium, liver and brain (10-650%), and enhanced the VitE levels in plasma (15-74%) and tissues (8-33%) by the end of the 80-day trial, proving better Se distribution and retention in pigs fed organic Se. Injecting lipopolysaccharide (LPS) intravenously half-way into the trial provoked a pyrogenic response in the pigs followed by a rapid increase of inorganic Se after 5-12 h, a drastic drop of SeMet levels between 12 and 24 h that recovered by 48 h, and a small increase of SeCys by 24-48 h, together with a gradual rise of GPx3, SelP and SeAlb in plasma up to 48 h. These changes in Se speciation in plasma were particularly significant (0.0024 > p > 0.00007) in pigs receiving SeMet- (0.44 mg Se/kg, above EU-legislated limits) or SeMix-supplemented (SeMet and NaSe both at 0.2 mg Se/kg, within EU-legislated limits) diets, which demonstrates Se metabolism upregulation to counteract the LPS-induced oxidative stress and a strengthened antioxidant capacity in these pigs. Overall, a Se source combination (without exceeding EU-legislated limits) and sufficient VitE supplementation (≥ 50 mg/kg) improved the pigs' antioxidant status, while doubling the allowed dietary organic Se increased the Se in tissues up to sixfold without compromising the animal's health due to toxicity. This study renders valuable results for revising the current dietary SeMet limits in swine rations.

Evaluation of digestively resistant or soluble fibers, short- and medium-chain fatty acids, trace minerals, and antibiotics in nonchallenged nursery pigs on performance, digestibility, and intestinal integrity

Three experiments (EXP) were conducted to determine the effect of feed additives on performance, intestinal integrity, gastrointestinal volatile fatty acids (VFA), and energy and nutrient digestion in nonchallenged nursery pigs. In EXP 1, 480 pigs (6.36-kg body weight, BW) were placed into 96 pens with 5 pigs/pen, and allotted to 1 of 10 dietary treatments: 1) negative control containing no feed additive (NC), 2) NC + 44 mg chlortetracycline and 38.5 mg tiamulin/kg diet (CTsb), 3) NC + 5% resistant potato starch (RSpo), 4) NC + 5% soluble corn fiber (SCF), 5) NC + 5% sugar beet pulp (SBP), 6) NC + 0.30% fatty acid mix (FAM), 7) NC + 0.10% phytogenic blend of essential oils and flavoring compounds (PHY), 8) NC + 50 mg Cu and 1,600 mg zinc oxide/kg diet (CuZn), 9) NC + 5% resistant corn starch (RScn), and 10) NC + 0.05% β-glucan (BG) for 28 d. There was no impact of dietary treatment on BW gain or feed intake (P ≥ 0.22). Pigs fed diets containing SCF, CTsb, and RSpo resulted in microbial community differences compared to pigs fed the NC (P < 0.05). In EXP 2, 48 barrows (12.8 kg BW) were selected at the end of EXP 1 and fed the same dietary treatments they had previously received: 1) NC, 2) NC + 5% RScn, 3) NC + 5% SCF, and 4) NC + FAM for 8 d. There was no effect of feeding diets containing RScn, SCF, or FAM on in vivo intestinal permeability (P ≤ 0.21). Ileal or colon pH, concentrations of VFA did not differ due to dietary treatment (P ≥ 0.36), but pigs fed diets containing FAM resulted in a greater butyric acid concentration in the cecum compared to pigs fed the NC (P ≤ 0.05). In EXP 3, 156 pigs (6.11 kg BW) were placed into 52 pens with 3 pigs/pen and allotted to 1 of 4 dietary treatments arranged in a factorial manner: 1) NC, 2) NC + 5% RSpo, 3) NC + 0.30% FAM, and 4) NC + 5% RSpo + 0.30% FAM for 24 d. Feeding pigs diets containing RSpo did not affect BW gain (P = 0.91) while pigs fed diets containing FAM grew improved BW gain (P = 0.09). Colonic butyric acid concentrations were greater in pigs fed diets containing RSpo (P = 0.03), while pigs fed diets containing FAM exhibited reduced total VFA concentrations (P = 0.11). The results indicate that supplementing diets with digestively resistant but fermentable fibers, short- and medium-chain fatty acids, or antibiotics do not have a consistent effect, positive or negative, on markers of intestinal integrity or barrier function, intestinal VFA patterns, ATTD of energy and nutrients, or on pig performance.

Residual feed intake in peripartal dairy cows is associated with differences in milk fat yield, ruminal bacteria, biopolymer hydrolyzing enzymes, and circulating biomarkers of immunometabolism

Residual feed intake (RFI) measures feed efficiency independent of milk production level, and is typically calculated using data past peak lactation. In the current study, we retrospectively classified multiparous Holstein cows (n = 320) from 5 of our published studies into most feed-efficient (M-eff) or least feed-efficient (L-eff) groups using performance data collected during the peripartal period. Objectives were to assess differences in profiles of plasma biomarkers of immunometabolism, relative abundance of key ruminal bacteria, and activities of digestive enzymes in ruminal digesta between M-eff and L-eff cows. Individual data from cows with ad libitum access to a total mixed ration from d -28 to d +28 relative to calving were used. A linear regression model including dry matter intake (DMI), energy-corrected milk (ECM), changes in body weight (BW), and metabolic BW was used to classify cows based on RFI divergence into L-eff (n = 158) and M-eff (n = 162). Plasma collected from the coccygeal vessel at various times around parturition (L-eff = 60 cows; M-eff = 47 cows) was used for analyses of 30 biomarkers of immunometabolism. Ruminal digesta collected via esophageal tube (L-eff = 19 cows; M-eff = 29 cows) was used for DNA extraction and assessment of relative abundance (%) of 17 major bacteria using real-time PCR, as well as activity of cellulase, amylase, xylanase, and protease. The UNIVARIATE procedure of SAS 9.4 (SAS Institute Inc.) was used for analyses of RFI coefficients. The MIXED procedure of SAS was used for repeated measures analysis of performance, milk yield and composition, plasma immunometabolic biomarkers, ruminal bacteria, and enzyme activities. The M-eff cows consumed less DMI during the peripartal period compared with L-eff cows. In the larger cohort of cows, despite greater overall BW for M-eff cows especially in the prepartum (788 vs. 764 kg), no difference in body condition score was detected due to RFI or the interaction of RFI × time. Milk fat content (4.14 vs. 3.75 ± 0.06%) and milk fat yield (1.75 vs. 1.62 ± 0.04 kg) were greater in M-eff cows. Although cumulative ECM yield did not differ due to RFI (1,138 vs. 1,091 ± 21 kg), an RFI × time interaction due to greater ECM yield was found in M-eff cows. Among plasma biomarkers studied, concentrations of nonesterified fatty acids, β-hydroxybutyrate, bilirubin, ceruloplasmin, haptoglobin, myeloperoxidase, and reactive oxygen metabolites were overall greater, and glucose, paraoxonase, and IL-6 were lower in M-eff compared with L-eff cows. Among bacteria studied, abundance of Ruminobacter amylophilus and Prevotella ruminicola were more than 2-fold greater in M-eff cows. Despite lower ruminal activity of amylase in M-eff cows in the prepartum, regardless of RFI, we observed a marked linear increase after calving in amylase, cellulase, and xylanase activities. Protease activity did not differ due to RFI, time, or RFI × time. Despite greater concentrations of biomarkers reflective of negative energy balance and inflammation, higher feed efficiency measured as RFI in peripartal dairy cows might be associated with shifts in ruminal bacteria and amylase enzyme activity. Further studies could help address such factors, including the roles of the liver and the mammary gland.

The effect of feed efficiency classification on visceral organ mass in finishing steers

Individual feed intake of crossbred beef steers (one contemporary group/year, 2 yr) was recorded during finishing to investigate visceral organ mass in steers divergent for feed efficiency. Based on residual feed intake (RFI), the 20% most efficient (HE, n = 8/year) and 20% least efficient (LE; n = 8/year) steers with 12th rib fat ≥1.02 cm were slaughtered. High efficiency steers had less DM intake (P < 0.001), greater G:F (P < 0.001), and similar ADG and hot carcass weight (HCW). High efficiency steers tended to have less (P ≤ 0.10) small intestinal mass (actual and relative to BW and HCW) in year 1. In year 2, HE steers tended to have greater (P ≤ 0.10) large intestinal actual and relative masses. Low efficiency steers tended to have greater (P = 0.06) actual omasum mass and had greater (P ≤ 0.03) relative omasum masses compared with HE. Stomach complex, total gastrointestinal tract, liver, and kidney masses tended to be greater (P ≤ 0.10) relative to BW, and were greater (P ≤ 0.05) relative to HCW, in LE. Data suggest that visceral organ mass, especially of the gastrointestinal tract, plays a role in overall metabolic efficiency of finishing steers.

Maternal Immune Activation and Dietary Soy Isoflavone Supplementation Influence Pig Immune Function but not Muscle Fiber Formation

The goals of this study were to determine the impact of maternal PRRSV infection on offspring muscle and immune development and the potential of dietary soy isoflavones to mitigate those effects. Thirteen first-parity gilts (“gilts”) were randomly allotted into one of three treatments: not infected and fed a diet devoid of isoflavones (CON), infected with porcine reproductive and respiratory syndrome virus (PRRSV) and fed the control diet (POS) or that supplemented with 1,500 mg/kg soy-derived isoflavones (ISF). Gilts were inoculated with PRRSV intranasally on gestational day (GD) 70. After farrowing (GD 114 ± 2), 1-2 offspring (“pigs”) closest to the average litter weight were selected either at birth (3 ± 2 d of age) or weaning (21 ±2 d of age) to determine body, muscle, and organ weights as well as muscle cell number and size. Four weaned pigs of average body weight within each litter were selected for postnatal immune challenge. At PND 52, pigs were injected with 5 µg/kg BW lipopolysaccharide (LPS) intraperitoneally. Serum was collected at 0, 4, and 8 h following LPS administration to analyze tumor necrosis factor alpha (TNF-α). At PND 59, pigs were administered a novel vaccine to elicit an adaptive immune response. At PND 59, 66, and 73, peripheral blood mononuclear cells were isolated and T-cell populations determined by flow cytometry. Both POS and ISF pigs exhibited persistent PRRSV infections throughout the study (PND 1-73). At PND 3, whole body, muscle, and organ weights were not different (P &gt; 0.22) between groups, with the exception of relative liver weight, which was increased (P &lt; 0.05) in POS compared with CON pigs. At PND 21, ISF pigs had reduced (P ≤ 0.05) whole body and muscle weights, but greater (P &lt; 0.05) kidney weight compared with CON, and greater (P &lt; 0.05) relative liver weight compared with CON and POS. Muscle fiber number and size were not different (P &gt; 0.39) between groups at birth or weaning. After LPS administration, TNF-α was greatest in ISF pigs (P &lt; 0.05) at both 0 and 8 h post-challenge. At the peak time-point of 4 h post-challenge, ISF pigs had the greatest concentration of TNF-α and CON pigs had the lowest, with POS pigs being intermediate (P = 0.01). After vaccination, ISF offspring had shifts in T-cell populations indicating an impaired immune response. These data indicate that maternal PRRSV infection may impact offspring organ growth and immune function, particularly when the dam is supplemented with isoflavones.

Effects of Dietary Tea Powder on the Growth Performance, Carcass Traits, and Meat Quality of Tibetan Pig × Bama Miniature Pigs

This study was conducted to evaluate the effects of tea powder in diets on the growth performance, meat quality, muscular amino acid, fatty acid profile, and serum biochemical indices of pigs. A total of 120 local Chinese pigs (Tibetan × Bama miniature pigs) were randomly assigned to five treatment groups, each with six pens and four pigs per pen. During a 60-day experiment, these groups of pigs were fed the normal diet and the diet supplemented with 1%, 2%, 4%, and 6% tea powder, respectively. The results showed that the supplementation of tea powder did not affect the growth performance of pigs. However, the dietary tea powder inclusion decreased (p < 0.05) the average fat thickness, total fat, and abdominal fat, and increased (p < 0.05) the total muscle as well. In addition, the dietary 2% tea powder decreased (p < 0.05) the muscle lightness (L*) and yellowness (b*). Compared with the control group, the dietary supplementation with 1%, 2%, and 4% tea powder raised (p < 0.05) the total amino acids (TAA) and essential amino acids (EAA), and dietary 4% and 6% tea powder increased (p < 0.05) the C20:5n3 in the muscle tissue. Furthermore, the serum lipid metabolism-related biochemical indices and mRNA expression levels were improved with the addition of tea powder. These results indicated that dietary tea powder might improve the carcass traits and meat quality of the Chinese native finishing pigs, but it does not affect their growth performance. Tea powder could be fully developed and reasonably applied as a dietary supplement.

Evaluation of the Fecal Bacterial Communities of Angus Steers With Divergent Feed Efficiencies Across the Lifespan From Weaning to Slaughter

Numerous studies have examined the link between the presence of specific gastrointestinal bacteria and the feed efficiency of cattle. However, cattle undergo dietary changes during their productive life which can cause fluctuations in their microbial consortium. The objective of the present study was to assess changes in the fecal microbiome of beef steers genetically selected to be divergent in feedlot feed efficiency, to determine whether differences in their fecal microbiomes could be detected as early as weaning, and continued throughout the rearing process regardless of dietary changes. Fecal samples were collected at weaning, yearling age, and slaughter for a group of 63 steers. Based on their feedlot-finishing performance, the steers were selected and divided into two groups according to their residual feed intake (RFI): efficient steers (low-RFI; n = 7) and inefficient steers (high-RFI; n = 8). To ascertain the fecal microbial consortium and volatile fatty acid (VFA) content, 16S rRNA gene sequencing and VFA analysis were performed. Overall, bacterial evenness and diversity were greater at weaning compared to yearling and slaughter for both efficiency groups (P < 0.001). Feedlot RFI linearly decreased as both Shannon diversity and Ruminococcaceae abundance increased (R² = 65.6 and 60.7%, respectively). Abundances of Ruminococcaceae, Rikenellaceae, and Christensenellaceae were higher at weaning vs. yearling age and slaughter (P < 0.001); moreover, these families were consistently more abundant in the feces of the low-RFI steers (for most of the timepoints evaluated; P ≤ 0.05), compared to the high-RFI steers. Conversely, abundances of Bifidobacteriaceae were numerically higher in the feces of the high-RFI steers throughout their lifespan. Total VFA concentrations increased at slaughter compared to weaning and yearling for both efficiency groups (P < 0.001). The acetate:propionate ratio decreased linearly (P < 0.001) throughout the life of the steers regardless of their efficiency, reflective of dietary changes. Our results indicate that despite fluctuations due to animal age and dietary changes, specific bacterial families may be correlated with feed efficiency of steers. Furthermore, such differences may be identifiable at earlier stages of the production cycle, potentially as early as weaning.

Impact of Intestinal Microbiota on Growth and Feed Efficiency in Pigs: A Review

This review summarises the evidence for a link between the porcine intestinal microbiota and growth and feed efficiency (FE), and suggests microbiota-targeted strategies to improve productivity. However, there are challenges in identifying reliable microbial predictors of host phenotype; environmental factors impact the microbe–host interplay, sequential differences along the intestine result in segment-specific FE- and growth-associated taxa/functionality, and it is often difficult to distinguish cause and effect. However, bacterial taxa involved in nutrient processing and energy harvest, and those with anti-inflammatory effects, are consistently linked with improved productivity. In particular, evidence is emerging for an association of Treponema and methanogens such as Methanobrevibacter in the small and large intestines and Lactobacillus in the large intestine with a leaner phenotype and/or improved FE. Bacterial carbohydrate and/or lipid metabolism pathways are also generally enriched in the large intestine of leaner pigs and/or those with better growth/FE. Possible microbial signalling routes linked to superior growth and FE include increased intestinal propionate production and reduced inflammatory response. In summary, the bacterial taxa and/or metabolic pathways identified here could be used as biomarkers for FE/growth in pigs, the taxa exploited as probiotics or the taxa/functionality manipulated via dietary/breeding strategies in order to improve productivity in pigs.

Chronic heat stress regulates the relation between heat shock protein and immunity in broiler small intestine

Chronic heat stress is considered to decrease the immune functions which makes negative effect on broiler growth performance. Here, we investigated the relationship between chronic heat stress, growth performance, and immunity in the small intestine of broilers. The study included two groups (control and heat stressed group) with eight replications per group. Ten broilers of 20-day aged were allocated in each replication. On day 35, the treatment group was subdivided into two groups based on their body weights (heavy and low body weight). Although, there was only the control and treatment group on day 28. The growth performance decreased and expression of heat shock protein 70 (HSP70), HSP60, and HSP47 increased on days 28 and 35 in the chronic heat stress group as compared with those in the control group. The expression levels of HSPs were significantly higher in the low body weight group than in the control group. The genes HSP70 and HSP60 were significantly associated with pro- and anti-inflammatory cytokines in the small intestine of the broilers of the treatment group. Thus, HSP70 and HSP60 activated the adaptive immunity in the small intestines of the broilers from the treatment group to allow adaptation to chronic heat stress environment.

Exploring the Regulatory Potential of Long Non-Coding RNA in Feed Efficiency of Indicine Cattle

Long non-coding RNA (lncRNA) can regulate several aspects of gene expression, being associated with complex phenotypes in humans and livestock species. In taurine beef cattle, recent evidence points to the involvement of lncRNA in feed efficiency (FE), a proxy for increased productivity and sustainability. Here, we hypothesized specific regulatory roles of lncRNA in FE of indicine cattle. Using RNA-Seq data from the liver, muscle, hypothalamus, pituitary gland and adrenal gland from Nellore bulls with divergent FE, we submitted new transcripts to a series of filters to confidently predict lncRNA. Then, we identified lncRNA that were differentially expressed (DE) and/or key regulators of FE. Finally, we explored lncRNA genomic location and interactions with miRNA and mRNA to infer potential function. We were able to identify 126 relevant lncRNA for FE in Bos indicus, some with high homology to previously identified lncRNA in Bos taurus and some possible specific regulators of FE in indicine cattle. Moreover, lncRNA identified here were linked to previously described mechanisms related to FE in hypothalamus-pituitary-adrenal axis and are expected to help elucidate this complex phenotype. This study contributes to expanding the catalogue of lncRNA, particularly in indicine cattle, and identifies candidates for further studies in animal selection and management.

Colonic microbiome profiles for improved feed efficiency can be identified despite major effects of farm of origin and contemporary group in pigs

While feed efficiency (FE) is a trait of great economic importance to the pig industry, the influence of the intestinal microbiome in determining FE is not well understood. The objective of this experiment was to determine the relative influence of FE and farm of birth on the pig colonic microbiome. Animals divergent in residual feed intake (RFI) were sourced from two geographically distinct locations (farms A + B) in Ireland. The 8 most efficient (low RFI (LRFI)) and 8 least efficient (high RFI, (HRFI)) pigs from farm A and 12 LRFI and 12 HRFI pigs from farm B were sacrificed. Colonic digesta was collected for microbial analysis using 16S ribosomal RNA gene sequencing and also for volatile fatty acid analysis. The α-diversity differed between the farms in this study, with pigs from farm A having greater diversity based on Shannon and InvSimpson measures compared to pigs from farm B (P < 0.05), with no difference identified in either Chao1 or observed measures of diversity (P > 0.05). In the analysis of β-diversity, pigs clustered based on farm of birth rather than RFI. Variation in the management of piglets, weight of the piglets, season of the year, sanitary status and dam dietary influence could potentially be causative factors in this large variation between farms. However, despite significant variation in the microbial profile between farms, consistent taxonomic differences were identified between RFI groups. Within the phylum Bacteroidetes, the LRFI pigs had increased abundance of BS11 (P < 0.05) and a tendency toward increased Bacteroidaceae (P < 0.10) relative to the HRFI group. At genus level, the LRFI pigs had increased abundance of Colinsella (P < 0.05), a tendency toward increased Bacteroides and CF231 (P < 0.10). At species level, Ruminococcus flavefaciens had increased abundance in the LRFI compared to the HRFI animals. In conclusion, while farm of birth has a substantial influence on microbial diversity in the pig colon, a microbial signature indicative of FE status was apparent.

Different Sources of High Fat Diet Induces Marked Changes in Gut Microbiota of Nursery Pigs

Fat is one of the most important nutrients which provides concentrated energy and essential fatty acids. High fat diet markedly changes the gut microbial composition in mammals, whereas little is known about the impact of fat type on gut microbiome. This study was to evaluate the effects of fat sources on intestinal microbiota of nursery pigs. Eighteen pigs (28 days of age, 8.13 ± 0.10 kg BW) were housed individually (n = 6 per treatment) and allotted to three treatments based on a randomized complete block design. Pigs were fed basal diets with three different fat sources: 6.0% soybean oil (SBO), 6.0% palm oil (PO), and 7.5% encapsulated palm oil (EPO, contains 80% palm oil) respectively. Pigs were euthanized after 28 days of ad libitum feeding, and the digesta in the distal duodenum, jejunum, ileum, cecum and colon of each pig were obtained for microbial composition analysis. Correlation analyses were also performed between microbial composition with nutrients digestibility or growth performance. The results showed that pigs fed PO had marked changes in the bacteria community composition with increasing the richness and diversity in duodenum and jejunum (P < 0.05). Increased abundances of Proteobacteria in duodenum, jejunum and cecum, and decreased abundance of Firmicutes in jejunum were observed in pigs fed PO compared to SBO and EPO. Pigs fed EPO decreased abundances of Proteobacteria in duodenum and jejunum, and increased abundance of Firmicutes compared to pigs fed PO, and was similar to pigs fed SBO. The microbial changes (genus) had significant negative correlation with the fat digestibility. These results indicate that palm oil supplementation in nursery pig diet alters the gut microbial composition, with the most significant changes observed in small intestine. Encapsulation of palm oil, which helps increase the digestibility of palm oil, have beneficial effect on the microbial disturbance caused by palm oil supplementation. Our findings provide a better understanding of how different fat types influence microbial composition in different parts of the intestinal tract and the correlation between bacteria composition and nutrients digestibility, which may provide a new perspective for the rational application of fat in diet.

Host-Microbiota Interactions in Ileum and Caecum of Pigs Divergent in Feed Efficiency Contribute to Nutrient Utilization

The composition of the intestinal microbiota plays an important role in the digestion and utilization of nutrients and for gut health. Low-fiber diets stimulate digestion and absorption processes, predominantly in the upper region of the gastrointestinal tract, thereby increasing the conversion of feed into body weight. As a consequence, the chemical composition of digesta after duodenal and jejunal absorption processes and passage has a limited complexity affecting colonization and molecular profiles of enterocytes in the hind gut. To decipher ileal and caecal microbial ecosystems and host transcriptional profiles that are beneficial for effective use of the remaining nutrients, pigs differing in feeding efficiency were studied. Biological functions that were consistently enriched at both the gene and microbiota levels comprise immunity-related processes, which ensure the integrity of the gastrointestinal tract. In addition, the differential abundance of certain genera, including Rothia, Subdoligranulu, Leeia and Cellulosilyticum, reflects the establishment of a microbial profile that supports the digestion of endogenously indigestible dietary components in highly feed-efficient pigs. Overall, the results indicate the potential to promote these beneficial functions and further improve feed efficiency through manipulation of dietary and probiotic strategies.

Impact of repeated lipopolysaccharide administration on ovarian signaling during the follicular phase of the estrous cycle in post-pubertal pigs

Increased circulating lipopolysaccharide (LPS) results from heat stress (HS) and bacterial infection, both of which are associated with reduced female fertility. Specific effects of low-level, repeated LPS exposure on the ovary are unclear, as many studies utilize a bolus model and/or high dosage paradigm. To better understand the effects of chronic LPS exposure on ovarian signaling and function, post-pubertal gilts (n = 20) were orally administered altrenogest for 14 d to synchronize the beginning of the follicular phase of the ovarian cycle. For 5 d after synchronization, gilts (163 ± 3 kg) received IV administration of LPS (0.1 µg/kg BW, n = 10) or saline (CT, n = 10) 4× daily. Blood samples were obtained on days 1, 3, and 5 of LPS treatment. Follicular fluid was aspirated from dominant follicles on day 5, and whole ovarian homogenate was used for transcript and protein abundance analysis via quantitative real-time PCR and western blotting, respectively. There were no treatment differences detected in rectal temperature on any day (P ≥ 0.5). Administering LPS increased plasma insulin (P < 0.01), LPS-binding protein (LBP; P < 0.01), and glucose (P = 0.08) on day 1, but no treatment differences thereafter were observed (P = 0.66). There were no treatment differences in follicular fluid concentration of LBP or 17β-estradiol (P = 0.42). Gilts treated with LPS had increased abundance of ovarian TLR4 protein (P = 0.01), but protein kinase B (AKT) and phosphorylated AKT (pAKT) were unchanged and no effect of LPS on components of the phosphatidylinositol 3 kinase (PI3K) pathway were observed. There was no impact of LPS on ovarian abundance of STAR or CYP19A1, nor ESR1, LDLR, CYP19A1, CYP17A1, or 3BHSD. In conclusion, repeated, low-level LPS administration alters inflammatory but not steroidogenic or PI3K signaling in follicular phase gilt ovaries.

Identification of Important Proteins and Pathways Affecting Feed Efficiency in DLY Pigs by iTRAQ-Based Proteomic Analysis

Simple Summary

Feed efficiency is one of the most valuable economic traits in the pig industry. The small intestine is the site where most of the nutrients are absorbed from ingested food. Here, we studied the relationship between small intestinal proteomics and feed efficiency in Duroc × (Landrace × Yorkshire) pigs, which is the most popular commercial pig in the Chinese pork market. Exploring the molecular mechanisms of feed efficiency will create great value for the pig industry. Our research provided a reference for further understanding of the key proteins that affect small intestinal microvilli formation and the important pathways related to feed efficiency in pigs.

Abstract

Feed efficiency is an economically important trait controlled by multiple genes in pigs. The small intestine is the main organ of digestion and nutrient absorption. To explore the biological processes by which small intestine proteomics affects feed efficiency (FE), we investigated the small intestinal tissue proteomes of high-FE and low-FE pigs by the isobaric tag for relative and absolute quantification (iTRAQ) method. In this study, a total of 225 Duroc × (Landrace × Yorkshire) (DLY) commercial pigs were ranked according to feed efficiency, which ranged from 30 kg to 100 kg, and six pigs with extreme phenotypes were selected, three in each of the high and low groups. A total of 1219 differentially expressed proteins (DEPs) were identified between the high-FE and low-FE groups (fold change ≥1.2 or ≤0.84; p ≤ 0.05), of which 785 were upregulated, and 484 were downregulated. Enrichment analysis indicated that the DEPs were mainly enriched in actin filament formation, microvilli formation, and small intestinal movement pathways. Protein functional analysis and protein interaction networks indicated that RHOA, HCLS1, EZR, CDC42, and RAC1 were important proteins that regulate FE in pigs. This study provided new insights into the important pathways and proteins involved in feed efficiency in pigs.

Acute systemic inflammatory response to lipopolysaccharide stimulation in pigs divergently selected for residual feed intake

Background

It is unclear whether improving feed efficiency by selection for low residual feed intake (RFI) compromises pigs’ immunocompetence. Here, we aimed at investigating whether pig lines divergently selected for RFI had different inflammatory responses to lipopolysaccharide (LPS) exposure, regarding to clinical presentations and transcriptomic changes in peripheral blood cells.

Results

LPS injection induced acute systemic inflammation in both the low-RFI and high-RFI line (n = 8 per line). At 4 h post injection (hpi), the low-RFI line had a significantly lower (p = 0.0075) mean rectal temperature compared to the high-RFI line. However, no significant differences in complete blood count or levels of several plasma cytokines were detected between the two lines. Profiling blood transcriptomes at 0, 2, 6, and 24 hpi by RNA-sequencing revealed that LPS induced dramatic transcriptional changes, with 6296 genes differentially expressed at at least one time point post injection relative to baseline in at least one line (n = 4 per line) (|log₂(fold change)| ≥ log₂(1.2); q < 0.05). Furthermore, applying the same cutoffs, we detected 334 genes differentially expressed between the two lines at at least one time point, including 33 genes differentially expressed between the two lines at baseline. But no significant line-by-time interaction effects were detected. Genes involved in protein translation, defense response, immune response, and signaling were enriched in different co-expression clusters of genes responsive to LPS stimulation. The two lines were largely similar in their peripheral blood transcriptomic responses to LPS stimulation at the pathway level, although the low-RFI line had a slightly lower level of inflammatory response than the high-RFI line from 2 to 6 hpi and a slightly higher level of inflammatory response than the high-RFI line at 24 hpi.

Conclusions

The pig lines divergently selected for RFI had a largely similar response to LPS stimulation. However, the low-RFI line had a relatively lower-level, but longer-lasting, inflammatory response compared to the high-RFI line. Our results suggest selection for feed efficient pigs does not significantly compromise a pig’s acute systemic inflammatory response to LPS, although slight differences in intensity and duration may occur.

Analysis of the basal colonic innate immune response of pigs divergent in feed efficiency and following an ex vivo lipopolysaccharide challenge

While feed efficiency is influenced by multiple physiological processes, it is not known how efficient and inefficient pigs differ in relation to their basal immune response, and particularly their innate immune response to a microbial challenge. Hence, the objective was to examine the expression of genes encoding innate immune response markers in basal colonic tissue and colonic tissue following an ex vivo lipopolysaccharide (LPS) challenge from pigs divergent in residual feed intake (RFI). Pigs that differed in RFI were selected from two different farms of origin. Colonic tissue was harvested from high RFI (HRFI) and low (LRFI) pigs, and two experimental conditions were explored: the first was basal unchallenged tissue and the second was colonic tissue following an ex vivo LPS challenge. RNA was extracted and tested on a Nanostring panel of 72 genes coding for barrier defense proteins, transmembrane receptors, kinases, transcription regulators, cytokines, and cytokine regulators. In the basal unchallenged tissue, the LRFI pigs had increased expression of AOAH, AP1, and TRAM and the cytokines TNF, IL10, and CXCL8, compared with the HRFI pigs (P < 0.05), with a significant effect of farm of origin on 31 genes (P < 0.05). In the LPS-challenged tissues, the LRFI group had higher expression of TLR1, TLR7, TLR8, GPR43/FFAR2, JAK2, and NFAM1 compared with the HRFI group (P < 0.05). In conclusion, these data suggest that LRFI pigs have an upregulated basal colonic inflammatory state and a heightened response to an LPS challenge compared with the inefficient HRFI pigs. This immune profile potentially enhances their capacity to respond to an infectious challenge.

Responsiveness of swine divergently selected for feed efficiency to exogenous adrenocorticotropic hormone and glucose challenges

Increasing the feed efficiency of lean tissue gains is an important goal for improving sustainable pork production and profitability for swine producers. To study feed efficiency, genetic selection based on residual feed intake (RFI) was used to create two divergent lines. Low-RFI pigs consume less feed for equal weight gain compared with their less-efficient, high-RFI counterparts. As cortisol and insulin are important energy control and growth regulators, our objective was to evaluate the role of the adrenocorticotropic hormone (ACTH)-cortisol and the glucose-insulin axes in pigs divergently selected for RFI. Adrenocorticotropic hormone (0.2 IU/kg BW)-stimulated cortisol and non-esterified fatty acids (NEFA) concentrations and intravenous glucose tolerance test (IVGTT; 0.25 g/kg BW)-stimulated glucose, insulin, and NEFA concentrations were assessed in six low-RFI and six high-RFI gilts (68 ± 5.2 kg). Before the ACTH challenge, low-RFI gilts tended to have less baseline plasma cortisol (P = 0.08) but no difference in NEFA concentrations (P = 0.63) compared with high-RFI gilts. After the ACTH challenge, low-RFI gilts had less cortisol (P = 0.04) and NEFA concentrations (P = 0.05) compared with high-RFI gilts. Glucose, insulin, and NEFA concentrations did not differ between genetic lines before the IVGTT. After glucose infusion, low-RFI gilts had greater insulin concentrations (P = 0.003) but did not differ in glucose or NEFA concentrations compared with high-RFI gilts. These results indicate that genetic selection for reduced RFI (improved feed efficiency) resulted in less stress responsiveness and an increase in insulin after glucose infusion. These data have implications for identifying and selecting more feed efficient pigs and for understanding the physiological mechanisms underlying feed efficiency.

Porcine Feed Efficiency-Associated Intestinal Microbiota and Physiological Traits: Finding Consistent Cross-Locational Biomarkers for Residual Feed Intake

Optimal feed efficiency (FE) in pigs is important for economic and environmental reasons. Previous research identified FE-associated bacterial taxa within the intestinal microbiota of growing pigs. This study investigated whether FE-associated bacteria and selected FE-associated physiological traits were consistent across geographic locations (Republic of Ireland [ROI] [two batches of pigs, ROI1 and ROI2], Northern Ireland [NI], and Austria [AT]), where differences in genetic, dietary, and management factors were minimized. Pigs (n = 369) were ranked, within litter, on divergence in residual feed intake (RFI), and 100 extremes were selected (50 with high RFI and 50 with low RFI) across geographic locations for intestinal microbiota analysis using 16S rRNA amplicon sequencing and examination of FE-associated physiological parameters. Microbial diversity varied by geographic location and intestinal sampling site but not by RFI rank, except in ROI2, where more-feed-efficient pigs had greater ileal and cecal diversity. Although none of the 188 RFI-associated taxonomic differences found were common to all locations/batches, Lentisphaerae, Ruminococcaceae, RF16, Mucispirillum, Methanobrevibacter, and two uncultured genera were more abundant within the fecal or cecal microbiota of low-RFI pigs in two geographic locations and/or in both ROI batches. These are major contributors to carbohydrate metabolism, which was reflected in functional predictions. Fecal volatile fatty acids and salivary cortisol were the only physiological parameters that differed between RFI ranks. Despite controlling genetics, diet specification, dietary phases, and management practices in each rearing environment, the rearing environment, encompassing maternal influence, herd health status, as well as other factors, appears to impact intestinal microbiota more than FE.IMPORTANCE Interest in the role of intestinal microbiota in determining FE in pigs has increased in recent years. However, it is not known if the same FE-associated bacteria are found across different rearing environments. In this study, geographic location and intestinal sampling site had a greater influence on the pig gut microbiome than FE. This presents challenges when aiming to identify consistent reliable microbial biomarkers for FE. Nonetheless, seven FE-associated microbial taxa were common across two geographic locations and/or two batches within one location, and these indicated a potentially "healthier" and metabolically more capable microbiota in more-feed-efficient pigs. These taxa could potentially be employed as biomarkers for FE, although bacterial consortia, rather than individual taxa, may be more likely to predict FE. They may also merit consideration for use as probiotics or could be targeted by dietary means as a strategy for improving FE in pigs in the future.

A comparative analysis of the transcriptome profiles of liver and muscle tissue in pigs divergent for feed efficiency

BACKGROUND

The improvement of feed efficiency is a key economic goal within the pig production industry. The objective of this study was to examine transcriptomic differences in both the liver and muscle of pigs divergent for feed efficiency, thus improving our understanding of the molecular mechanisms influencing feed efficiency and enabling the identification of candidate biomarkers. Residual feed intake (RFI) was calculated for two populations of pigs from two different farms of origin/genotype. The 6 most efficient (LRFI) and 6 least efficient (HRFI) animals from each population were selected for further analysis of Longissimus Dorsi muscle (n = 22) and liver (n = 23). Transcriptomic data were generated from liver and muscle collected post-slaughter.

RESULTS

The transcriptomic data segregated based on the RFI value of the pig rather than genotype/farm of origin. A total of 6463 genes were identified as being differentially expressed (DE) in muscle, while 964 genes were identified as being DE in liver. Genes that were commonly DE between muscle and liver (n = 526) were used for the multi-tissue analysis. These 526 genes were associated with protein targeting to membrane, extracellular matrix organisation and immune function. In the muscle-only analysis, genes associated with RNA processing, protein synthesis and energy metabolism were down regulated in the LRFI animals while in the liver-only analysis, genes associated with cell signalling and lipid homeostasis were up regulated in the LRFI animals.

CONCLUSIONS

Differences in the transcriptome segregated on pig RFI value rather than the genotype/farm of origin. Multi-tissue analysis identified that genes associated with GO terms protein targeting to membrane, extracellular matrix organisation and a range of terms relating to immune function were over represented in the differentially expressed genes of both liver and muscle.

Systems Biology Reveals NR2F6 and TGFB1 as Key Regulators of Feed Efficiency in Beef Cattle

Systems biology approaches are used as strategy to uncover tissue-specific perturbations and regulatory genes related to complex phenotypes. We applied this approach to study feed efficiency (FE) in beef cattle, an important trait both economically and environmentally. Poly-A selected RNA of five tissues (adrenal gland, hypothalamus, liver, skeletal muscle and pituitary) of eighteen young bulls, selected for high and low FE, were sequenced (Illumina HiSeq 2500, 100 bp, pared-end). From the 17,354 expressed genes considering all tissues, 1,335 were prioritized by five selection categories (differentially expressed, harboring SNPs associated with FE, tissue-specific, secreted in plasma and key regulators) and used for network construction. NR2F6 and TGFB1 were identified and validated by motif discovery as key regulators of hepatic inflammatory response and muscle tissue development, respectively, two biological processes demonstrated to be associated with FE. Moreover, we indicated potential biomarkers of FE, which are related to hormonal control of metabolism and sexual maturity. By using robust methodologies and validation strategies, we confirmed the main biological processes related to FE in Bos indicus and indicated candidate genes as regulators or biomarkers of superior animals.

GWAS and eQTL analysis identifies a SNP associated with both residual feed intake and GFRA2 expression in beef cattle

Residual feed intake (RFI), a measure of feed efficiency, is an important economic and environmental trait in beef production. Selection of low RFI (feed efficient) cattle could maintain levels of production, while decreasing feed costs and methane emissions. However, RFI is a difficult and expensive trait to measure. Identification of single nucleotide polymorphisms (SNPs) associated with RFI may enable rapid, cost effective genomic selection of feed efficient cattle. Genome-wide association studies (GWAS) were conducted in multiple breeds followed by meta-analysis to identify genetic variants associated with RFI and component traits (average daily gain (ADG) and feed intake (FI)) in Irish beef cattle (n = 1492). Expression quantitative trait loci (eQTL) analysis was conducted to identify functional effects of GWAS-identified variants. Twenty-four SNPs were associated (P < 5 × 10^-5) with RFI, ADG or FI. The variant rs43555985 exhibited strongest association for RFI (P = 8.28E-06). An eQTL was identified between this variant and GFRA2 (P = 0.0038) where the allele negatively correlated with RFI was associated with increased GFRA2 expression in liver. GFRA2 influences basal metabolic rates, suggesting a mechanism by which genetic variation may contribute to RFI. This study identified SNPs that may be useful both for genomic selection of RFI and for understanding the biology of feed efficiency.

Differences in intestinal size, structure, and function contributing to feed efficiency in broiler chickens reared at geographically distant locations

The contribution of the intestinal tract to differences in residual feed intake (RFI) has been inconclusively studied in chickens so far. It is also not clear if RFI-related differences in intestinal function are similar in chickens raised in different environments. The objective was to investigate differences in nutrient retention, visceral organ size, intestinal morphology, jejunal permeability and expression of genes related to barrier function, and innate immune response in chickens of diverging RFI raised at 2 locations (L1: Austria; L2: UK). The experimental protocol was similar, and the same dietary formulation was fed at the 2 locations. Individual BW and feed intake (FI) of chickens (Cobb 500FF) were recorded from d 7 of life. At 5 wk of life, chickens (L1, n = 157; L2 = 192) were ranked according to their RFI, and low, medium, and high RFI chickens were selected (n = 9/RFI group, sex, and location). RFI values were similar between locations within the same RFI group and increased by 446 and 464 g from low to high RFI in females and males, respectively. Location, but not RFI rank, affected growth, nutrient retention, size of the intestine, and jejunal disaccharidase activity. Chickens from L2 had lower total body weight gain and mucosal enzyme activity but higher nutrient retention and longer intestines than chickens at L1. Parameters determined only at L1 showed increased crypt depth in the duodenum and jejunum and enhanced paracellular permeability in low vs. high RFI females. Jejunal expression of IL1B was lower in low vs. high RFI females at L2, whereas that of TLR4 at L1 and MCT1 at both locations was higher in low vs. high RFI males. Correlation analysis between intestinal parameters and feed efficiency metrics indicated that feed conversion ratio was more correlated to intestinal size and function than was RFI. In conclusion, the rearing environment greatly affected intestinal size and function, thereby contributing to the variation in chicken RFI observed across locations.

Feed-efficient pigs exhibit molecular patterns allowing a timely circulation of hormones and nutrients

Feed efficiency (FE) is a measure of the rate between feed intake and body weight gain and is subject to constant progress in pigs, based on extensive performance tests and analyses of physiological parameters. However, endocrine regulatory circuits that comprise the sensation and perception of intrinsic requirements and appropriate systemic responses have not yet been fully elucidated. It is hypothesized that the gut-brain axis, which is a network of hierarchical anterior regulatory tissues, contributes largely to variations in FE. Therefore, full-sib pigs with extreme residual feed intake values were assigned to experimental groups of high and low FE. Relevant hormones, minerals, and metabolites including fatty acid profiles were analyzed in serum to assess postprandial conditions. Transcriptome profiles were deduced from intestinal (duodenum, jejunum, ileum) and neuroendocrine tissues (hypothalamus). Serum analyses of feed-efficient animals showed an increased content of the incretin GIP, calcium, magnesium, β-hydroxybutyric acid, and fat compared with low-FE pigs. Complementary expression profiles in intestinal tissues indicate a modulated permeability and host-microbe interaction in FE-divergent pigs. Transcriptomic analyses of the hypothalamus showed that differences between the FE groups in appetite and satiety regulation are less pronounced. However, hypothalamic abundance of transcripts like ADCY7, LHCGR, and SLC2A7 and molecular signatures in local and systemic tissue sites indicate that increased allocation and circulation of energy equivalents, minerals, and hormones are promoted in feed-efficient animals. Overall, patterns of gastrointestinal hormones and gene expression profiles identified host-microbiota interaction, intestinal permeability, feed intake regulation, and energy expenditure as potential mechanisms affecting FE in pigs.

Interactions between metabolically active bacteria and host gene expression at the cecal mucosa in pigs of diverging feed efficiency

Little is known about the role of the gut mucosal microbiota and microbe-host signaling in the variation of pig's feed efficiency (FE). This study therefore aimed to investigate the FE-related differences in the metabolically active mucosal bacterial microbiota and expression of genes for innate immune response, barrier function, nutrient uptake, and incretins in the cecum of finishing pigs. Pigs (n = 72) were ranked for their residual feed intake (RFI; metric for FE) between days 42 and 91 postweaning and were stratified within litter and sex into high (HRFI; n = 8) and low RFI (LRFI; n = 8). Cecal mucosa and digesta were collected on day 137-141 of life. After isolating total RNA from the mucosa, the RNA was transcribed into cDNA which was used for gene expression analysis, total bacterial quantification, and high-throughput sequencing (Illumina MiSeq) of the hypervariable V3-V4 region of the 16S rRNA gene. The RFI differed by 2.1 kg between low RFI (LRFI; good FE) and high RFI (HRFI; poor FE) pigs (P < 0.001). The cecal mucosa was mainly colonized by Helicobacteraceae, Campylobacteraceae, Veillonellaceae, Lachnospiraceae, and Prevotellaceae. Despite the lack of differences in microbial diversity and absolute abundance, RFI-associated compositional differences were found. The predominant genus Campylobacter tended (P < 0.10) to be 0.4-fold more abundant in LRFI pigs, whereas low abundant Escherichia/Shigella (P < 0.05), Ruminobacter (P < 0.05), and Veillonella (P < 0.10) were 3.4-, 6.6-, and 4.4-fold less abundant at the cecal mucosa of LRFI compared to HRFI pigs. Moreover, mucin 2 and zona occludens-1 were less expressed (P < 0.05) in the cecal mucosa of LRFI compared to HRFI pigs. Cecal mucosal expression of monocarboxylate transporter-1, glucagon-like peptide-1, and peptide YY further tended (P < 0.10) to be downregulated in LRFI compared to HRFI pigs, indicating an enhanced VFA uptake and signaling in HRFI pigs. Sparse partial least square regression and relevance networking support the hypothesis that certain mucosal bacteria and luminal microbial metabolites were more associated than others with differences in RFI and cecal gene expression. However, present results do not allow the determination of whether mucosal bacterial changes contributed to variation in FE or were rather a consequence of FE-related changes in the pig's physiology or feeding behavior.

Diurnal heat stress reduces pig intestinal integrity and increases endotoxin translocation

Heat stress negatively affects performance and intestinal integrity of pigs. The objective of this study was to characterize the effects of diurnal heat stress (dHS) on nursery-grower pig performance, intestinal integrity, and lipopolysaccharide (LPS) translocation. Forty-eight nursery-grower gilts, individually penned, were randomly assigned to two treatments. Twenty-four pigs were then exposed to dHS for 3 d, 6 h at 38°C and 18 h at 32°C, at 40-60% humidity. The remaining pigs were maintained under thermal neutral (TN) conditions. Changes in pig rectal temperatures (Tr), respiration rates (RR), performance, and blood parameters were evaluated. Additionally, ex vivo ileum integrity was assessed with the Ussing chamber by measuring transepithelial resistance (TER), and 4 kDa fluorescein isothiocyanate (FITC)-dextran (FD4) and FITC-LPS mucosal to serosal flux. As expected, dHS increased pig Tr and RR (P < 0.05) and reduced pig performance (P < 0.05) on the 3-d period. Compared with TN, ileum TER (P = 0.04), FITC-LPS (P < 0.001), and FD4 (P = 0.011) permeability were significantly increased due to dHS. Compared with TN pigs, dHS increased serum endotoxin by 150% (P = 0.031). Altogether, 3-d dHS significantly reduced pig performance and intestinal integrity and increased blood endotoxin concentrations.

Differentially expressed genes in the caecal and colonic mucosa of Landrace finishing pigs with high and low food conversion ratios

The feed conversion ratio (FCR) is an essential economic trait for pig production, and is directly related to feed efficiency. Studies identifying the differential expression of functional genes involved in biological and molecular mechanisms in the intestine in relation to growth performance are rare. In this study, RNA-Seq was used to identify transcriptomes in caecal and colonic mucosal tissues in order to determine the differential expression of genes from two full-sibling pairs and two half-sibling pairs of Landrace finishing pigs with opposing FCR phenotypes. In total, 138 (comparison of high and low FCR in caecal mucosa), 64 (comparison of high and low FCR in colonic mucosa), and 165 (contrast between the caecal and colonic mucosa) differentially expressed genes were identified. Some of these genes were functionally related to energy and lipid metabolism, particularly short chain fatty acids metabolism, as well as gastrointestinal peristalsis and ion transport. Functional annotation were performed to identify differentially expressed genes, such as GUCA2A, GUCA2B, HSP70.2, NOS2, PCK1, SLCs, and CYPs, which may positively influence feed efficiency in Landrace pigs. These differentially expressed genes need to be further tested for candidate genes that are related to feed efficiency.

Effects of porcine epidemic diarrhea virus infection on nursery pig intestinal function and barrier integrity

The pig intestinal epithelium can be compromised by pathogens leading to reduced integrity and function. Porcine epidemic diarrhea virus (PEDV), recently detected in North America, exemplifies intestinal epithelial insult. Although several studies have investigated the molecular aspects and host immune response to PEDV, there are little data on the impact of PEDV on pig intestinal physiology. The objective of this study was to investigate the longitudinal impact of PEDV on nursery pig intestinal function and integrity. Fifty recently-weaned, 5-week-old barrows and gilts (BW=9.92±0.49kg) were sorted based on body weight (BW) and sex into two treatments: 1) Control or 2) PEDV inoculated. At 2, 5, 7, and 14days post inoculation (dpi), 4 pigs per treatment were euthanized and jejunum sections collected. PEDV antigen was detected in inoculated pigs by immunohistochemistry in 50% (2/4) at dpi 2, 100% (4/4) at dpi 5, and none at later time points. PEDV-infected pigs had reduced (P<0.05) villus height and decreased transepithelial resistance compared with controls. Total acidic mucins, particularly sialomucin, were reduced in PEDV pigs at dpi 2 and then increased compared with controls at dpi 7 and 14. In addition, PEDV pigs had increased stem cell proliferation (P<0.05) and a numerical increase in DNA fragmentation compared with controls through dpi 7 which coincided with an observed return of digestive function to that of controls. Collectively, these data reveal that PEDV infection results in time-dependent changes not only in intestinal morphology but also barrier integrity and function.

Probiotic roles of Lactobacillus sp. in swine: insights from gut microbiota

The use of lactobacilli as probiotics in swine has been gaining attention due to their ability to improve growth performance and carcass quality, prevent gastrointestinal infection and most importantly, their 'generally recognized as safe' status. Previous studies support the potential of lactobacilli to regulate host immune systems, enhance gut metabolic capacities and maintain balance in the gut microbiota. Research on swine gut microbiota has revealed complex gut microbial community structure and showed the importance of Lactobacillus to the host's health. However, the species- and strain-specific characteristics of lactobacilli that confer probiotic benefits are still not well understood. The diversity of probiotic traits in a complex gut ecosystem makes it challenging to infer the relationships between specific functions of Lactobacillus sp. and host health. In this review, we provide an overview of how lactobacilli play a pivotal role in the swine gut ecosystem and identify key characteristics that influence gut microbial community structure and the health of pigs. In addition, based on recent and ongoing meta-omics and omics research on the gut microbiota of pigs, we suggest a workflow combining culture-dependent and culture-independent approaches for more effective selection of probiotic lactobacilli.

Finishing pigs that are divergent in feed efficiency show small differences in intestinal functionality and structure

Controversial information is available regarding the feed efficiency-related variation in intestinal size, structure and functionality in pigs. The present objective was therefore to investigate the differences in visceral organ size, intestinal morphology, mucosal enzyme activity, intestinal integrity and related gene expression in low and high RFI pigs which were reared at three different geographical locations (Austria, AT; Northern Ireland, NI; Republic of Ireland, ROI) using similar protocols. Pigs (n = 369) were ranked for their RFI between days 42 and 91 postweaning and low and high RFI pigs (n = 16 from AT, n = 24 from NI, and n = 60 from ROI) were selected. Pigs were sacrificed and sampled on ~day 110 of life. In general, RFI-related variation in intestinal size, structure and function was small. Some energy saving mechanisms and enhanced digestive and absorptive capacity were indicated in low versus high RFI pigs by shorter crypts, higher duodenal lactase and maltase activity and greater mucosal permeability (P < 0.05), but differences were mainly seen in pigs from AT and to a lesser degree in pigs from ROI. Additionally, low RFI pigs from AT had more goblet cells in duodenum but fewer in jejunum compared to high RFI pigs (P < 0.05). Together with the lower expression of TLR4 and TNFA in low versus high RFI pigs from AT and ROI (P < 0.05), these results might indicate differences in the innate immune response between low and high RFI pigs. Results demonstrated that the variation in the size of visceral organs and intestinal structure and functionality was greater between geographic location (local environmental factors) than between RFI ranks of pigs. In conclusion, present results support previous findings that the intestinal size, structure and functionality do not significantly contribute to variation in RFI of pigs.

A transcriptome multi-tissue analysis identifies biological pathways and genes associated with variations in feed efficiency of growing pigs

BACKGROUND

Animal's efficiency in converting feed into lean gain is a critical issue for the profitability of meat industries. This study aimed to describe shared and specific molecular responses in different tissues of pigs divergently selected over eight generations for residual feed intake (RFI).

RESULTS

Pigs from the low RFI line had an improved gain-to-feed ratio during the test period and displayed higher leanness but similar adiposity when compared with pigs from the high RFI line at 132 days of age. Transcriptomics data were generated from longissimus muscle, liver and two adipose tissues using a porcine microarray and analyzed for the line effect (n = 24 pigs per line). The most apparent effect of the line was seen in muscle, whereas subcutaneous adipose tissue was the less affected tissue. Molecular data were analyzed by bioinformatics and subjected to multidimensional statistics to identify common biological processes across tissues and key genes participating to differences in the genetics of feed efficiency. Immune response, response to oxidative stress and protein metabolism were the main biological pathways shared by the four tissues that distinguished pigs from the low or high RFI lines. Many immune genes were under-expressed in the four tissues of the most efficient pigs. The main genes contributing to difference between pigs from the low vs high RFI lines were CD40, CTSC and NTN1. Different genes associated with energy use were modulated in a tissue-specific manner between the two lines. The gene expression program related to glycogen utilization was specifically up-regulated in muscle of pigs from the low RFI line (more efficient). Genes involved in fatty acid oxidation were down-regulated in muscle but were promoted in adipose tissues of the same pigs when compared with pigs from the high RFI line (less efficient). This underlined opposite line-associated strategies for energy use in skeletal muscle and adipose tissue. Genes related to cholesterol synthesis and efflux in liver and perirenal fat were also differentially regulated in pigs from the low vs high RFI lines.

CONCLUSIONS

Non-productive functions such as immunity, defense against pathogens and oxidative stress contribute likely to inter-individual variations in feed efficiency.

Comparison of electrogenic glucose transport processes and permeability between proximal and distal jejunum of laying hens

1. The current objective was to assess (1) differences in mucosal transepithelial short-circuit current (I_sc) and tissue conductance (G_T), (2) the effect of a glucose stimulus and (3) epithelial paracellular permeability in the proximal and distal jejunum of laying hens. 2. Proximal and distal jejunal segments used in the Ussing chambers were collected at 9 ± 0.5 and 73 ± 3.4% (SEM) of jejunal length, respectively. The proximal jejunal mucosa showed a small negative I_sc (-1.3 µA/cm²), whereas the distal jejunum had a higher I_sc (32.9 µA/cm²). Similarly, G_T was 2.5-fold greater in the distal compared to the proximal jejunum. 3. Increased paracellular permeability in the distal jejunum was displayed as demonstrated by a 5-fold higher mucosal to serosal flux of fluorescein isothiocyanate and horseradish peroxidase, representing molecules of low and high molecular weight, respectively. 4. Addition of glucose to the mucosal side (5 mmol/l, final concentration in the chamber) to stimulate an absorptive effect caused 3-fold greater G_T in the distal compared to the proximal jejunum. 5. In conclusion, the present results supported site-specific electrogenic transport processes for the jejunal mucosa of laying hens. Therefore, precise description of the jejunal site may contribute to an improved comparability of electrophysiological data.

Microbiota-host interplay at the gut epithelial level, health and nutrition

Growing evidence suggests the implication of the gut microbiota in various facets of health and disease. In this review, the focus is put on microbiota-host molecular cross-talk at the gut epithelial level with special emphasis on two defense systems: intestinal alkaline phosphatase (IAP) and inducible heat shock proteins (iHSPs). Both IAP and iHSPs are induced by various microbial structural components (e.g. lipopolysaccharide, flagellin, CpG DNA motifs), metabolites (e.g. n-butyrate) or secreted signal molecules (e.g., toxins, various peptides, polyphosphate). IAP is produced in the small intestine and secreted into the lumen and in the interior milieu. It detoxifies microbial components by dephosphorylation and, therefore, down-regulates microbe-induced inflammation mainly by inhibiting NF-κB pro-inflammatory pathway in enterocytes. IAP gene expression and enzyme activity are influenced by the gut microbiota. Conversely, IAP controls gut microbiota composition both directly, and indirectly though the detoxification of pro-inflammatory free luminal adenosine triphosphate and inflammation inhibition. Inducible HSPs are expressed by gut epithelial cells in proportion to the microbial load along the gastro-intestinal tract. They are also induced by various microbial components, metabolites and secreted molecules. Whether iHSPs contribute to shape the gut microbiota is presently unknown. Both systems display strong anti-inflammatory and anti-oxidant properties that are protective to the gut and the host. Importantly, epithelial gene expressions and protein concentrations of IAP and iHSPs can be stimulated by probiotics, prebiotics and a large variety of dietary components, including macronutrients (protein and amino acids, especially L-glutamine, fat, fiber), and specific minerals (e.g. calcium) and vitamins (e.g. vitamins K1 and K2). Some food components (e.g. lectins, soybean proteins, various polyphenols) may inhibit or disturb these systems. The general cellular and molecular mechanisms involved in the microbiota-host epithelial crosstalk and subsequent gut protection through IAP and iHSPs are reviewed along with their nutritional modulation. Special emphasis is also given to the pig, an economically important species and valuable biomedical model.

Dietary organic zinc attenuates heat stress-induced changes in pig intestinal integrity and metabolism

Dietary zinc (inorganic and organic or zinc AA complex forms) is essential for normal intestinal barrier function and regeneration of intestinal epithelium. Given that heat stress (HS) exposure can negatively affect intestinal integrity and caloric intake, possible nutritional mitigation strategies are needed to improve health, performance, and well-being. Therefore, our objective was to evaluate 2 dietary zinc sources and reduced caloric intake on intestinal integrity in growing pigs subjected to 12 h of HS. A total of 36 pigs were fed 1 of 2 diets: 1) a control diet (CON; 120 mg/kg of zinc from zinc sulfate) or 2) 60 mg/kg from zinc sulfate and 60 mg/kg from zinc AA complex (ZnAA). After 17 d, the CON pigs were then exposed to thermal neutral (TN) conditions with ad libitum intake (TN-CON), HS (37°C) with ad libitum intake (HS-CON), or pair-fed to HS intake under TN conditions (PFTN); the ZnAA pigs were exposed to only HS (HS-ZnAA). All pigs were sacrificed after 12 h of environmental exposure, and blood and tissue bioenergetics stress markers and ex vivo ileum and colon integrity were assessed. Compared with TN-CON, HS significantly ( < 0.05) increased rectal temperatures and respiration rates. Ileum villus and crypt morphology was reduced by both pair-feeding and HS. Both PFTN and HS-CON pigs also had reduced ileum integrity (dextran flux and transepithelial resistance) compared with the TN-CON pigs. However, ZnAA tended to mitigate the HS-induced changes in ileum integrity. Ileum mucin 2 protein abundance was increased due to HS and pair-feeding. Colonic integrity did not differ due to HS or PFTN treatments. Compared with the HS-CON, HS-ZnAA pigs tended to have reduced blood endotoxin concentrations. In conclusion, HS and reduced feed intake compromised intestinal integrity in pigs, and zinc AA complex source mitigates some of these negative effects.

Pigs that are divergent in feed efficiency, differ in intestinal enzyme and nutrient transporter gene expression, nutrient digestibility and microbial activity

Feed efficiency is an important trait in the future sustainability of pig production, however, the mechanisms involved are not fully elucidated. The objective of this study was to examine nutrient digestibility, organ weights, select bacterial populations, volatile fatty acids (VFA's), enzyme and intestinal nutrient transporter gene expression in a pig population divergent in feed efficiency. Male pigs (n=75; initial BW 22.4 kg SEM 2.03 kg) were fed a standard finishing diet for 43 days before slaughter to evaluate feed intake and growth for the purpose of calculating residual feed intake (RFI). Phenotypic RFI was calculated as the residuals from a regression model regressing average daily feed intake (ADFI) on average daily gain (ADG) and midtest BW0.60 (MBW). On day 115, 16 pigs (85 kg SEM 2.8 kg), designated as high RFI (HRFI) and low RFI (LRFI) were slaughtered and digesta was collected to calculate the coefficient of apparent ileal digestibility (CAID), total tract nutrient digestibility (CATTD), microbial populations and VFA's. Intestinal tissue was collected to examine intestinal nutrient transporter and enzyme gene expression. The LRFI pigs had lower ADFI (P<0.001), improved feed conversion ratio (P<0.001) and an improved RFI value relative to HRFI pigs (0.19 v. -0.14 SEM 0.08; P<0.001). The LRFI pigs had an increased CAID of gross energy (GE), and an improved CATTD of GE, nitrogen and dry matter compared to HRFI pigs (P<0.05). The LRFI pigs had higher relative gene expression levels of fatty acid binding transporter 2 (FABP2) (P<0.01), the sodium/glucose co-transporter 1 (SGLT1) (P<0.05), the glucose transporter GLUT2 (P<0.10), and the enzyme sucrase-isomaltase (SI) (P<0.05) in the jejunum. The LRFI pigs had increased populations of lactobacillus spp. in the caecum compared with HRFI pigs. In colonic digesta HRFI pigs had increased acetic acid concentrations (P<0.05). Differences in nutrient digestibility, intestinal microbial populations and gene expression levels of intestinal nutrient transporters could contribute to the biological processes responsible for feed efficiency in pigs.

Identification of Gene Networks for Residual Feed Intake in Angus Cattle Using Genomic Prediction and RNA-seq

Improvement in feed conversion efficiency can improve the sustainability of beef cattle production, but genomic selection for feed efficiency affects many underlying molecular networks and physiological traits. This study describes the differences between steer progeny of two influential Angus bulls with divergent genomic predictions for residual feed intake (RFI). Eight steer progeny of each sire were phenotyped for growth and feed intake from 8 mo. of age (average BW 254 kg, with a mean difference between sire groups of 4.8 kg) until slaughter at 14-16 mo. of age (average BW 534 kg, sire group difference of 28.8 kg). Terminal samples from pituitary gland, skeletal muscle, liver, adipose, and duodenum were collected from each steer for transcriptome sequencing. Gene expression networks were derived using partial correlation and information theory (PCIT), including differentially expressed (DE) genes, tissue specific (TS) genes, transcription factors (TF), and genes associated with RFI from a genome-wide association study (GWAS). Relative to progeny of the high RFI sire, progeny of the low RFI sire had -0.56 kg/d finishing period RFI (P = 0.05), -1.08 finishing period feed conversion ratio (P = 0.01), +3.3 kg^0.75 finishing period metabolic mid-weight (MMW; P = 0.04), +28.8 kg final body weight (P = 0.01), -12.9 feed bunk visits per day (P = 0.02) with +0.60 min/visit duration (P = 0.01), and +0.0045 carcass specific gravity (weight in air/weight in air-weight in water, a predictor of carcass fat content; P = 0.03). RNA-seq identified 633 DE genes between sire groups among 17,016 expressed genes. PCIT analysis identified >115,000 significant co-expression correlations between genes and 25 TF hubs, i.e. controllers of clusters of DE, TS, and GWAS SNP genes. Pathway analysis suggests low RFI bull progeny possess heightened gut inflammation and reduced fat deposition. This multi-omics analysis shows how differences in RFI genomic breeding values can impact other traits and gene co-expression networks.

A single oral dose of a polyglucosamine influences the bioavailability of [9-(14)C]-Oleic acid in adult female Göttingen minipigs

Background

Worldwide obesity has nearly doubled since 1980 and is a leading risk for global deaths, profoundly affecting morbidity, mortality, health-care costs, and professional and personal quality of life. Treatment of obesity and its consequences include lifestyle intervention, pharmacotherapy, and bariatric surgery. Polyglucosamines have been proposed as an alternative strategy for treating obesity, by reducing the amount of absorbed fat through interaction with dietary fat through various mechanisms. The objective of this study is to investigate the influence of polyglucosamine on the bioavailability of the model compound [9-¹⁴C]-oleic acid in female Göttingen minipigs.

Method

The study consisted of two treatment groups, each consisting of six adult female Göttingen minipigs with a catheterized vena jugularis to enable frequent blood sampling. One group served as the untreated group (control) and the other group was pre-treated with 2 tablets of 500 mg formoline L112. After 30 min, all animals were dosed orally with [9-¹⁴C]-oleic acid. Excreta and blood samples were collected for analysis of radioactivity from 48 h pre-dose up to 144 h post-dosing. At sacrifice, the liver and contents of the gastrointestinal tract were collected for radioanalysis.

Results

Upon treatment with polyglucosamine (formoline L112), the T_max of [¹⁴C]-oleic acid in plasma was shifted from 4 to 16 h, and the C_max decreased significantly from 14.1 μg/g to 3.3 μg/g. In addition, upon treatment with polyglucosamine the internal exposure to [¹⁴C]-oleic acid as reflected by the area under the curve during the 0–12 h post-dose time interval (AUC_0-12h), is significantly decreased to 32.9 % of the plasma value of [¹⁴C]-oleic acid in untreated animals. Even up to 24 h post-dose, the AUC_0-24h is significantly decreased to 50.7 % of the plasma value in untreated animals and this significant effect is prolonged up to 60 h post-dose.

Conclusions

This study shows that treatment with polyglucosamine (formoline L112) reduces (as judged by C_max & AUC) and delays (as judged by T_max) fat absorption from the gastrointestinal tract into the systemic circulation and limits peak exposure to free fatty acids which may contribute to a more beneficial condition in overweight humans.

The Effect of Divergence in Feed Efficiency on the Intestinal Microbiota and the Intestinal Immune Response in Both Unchallenged and Lipopolysaccharide Challenged Ileal and Colonic Explants

Feed efficiency is an important trait in pig production, with evidence to suggest that the efficiencies of a variety of biological systems contribute to variation in this trait. Little work has been conducted on the contribution of the intestinal innate immune response to divergence in feed efficiency. Hence, the objective of this study was to examine select bacterial populations and gene expression profiles of a range of targets relating to gut health and immunity in the intestine of pigs phenotypically divergent in feed efficiency in: a) the basal state; and (b) following an ex-vivo lipopolysaccharide (LPS) challenge of ileal and colonic tissue. Male pigs (initial BW 22.4 kg (SD = 2.03)) were fed a standard finishing diet for the final 43 days prior to slaughter to evaluate feed intake and growth for the purpose of calculating residual feed intake (RFI). On day 115, 16 animals (average weight 85 kg, SEM 2.8 kg), designated high RFI (HRFI) and low RFI (LRFI) were slaughtered. The LRFI pigs had increased lactobacillus spp. in the caecum compared to HRFI pigs (P < 0.05). RFI groups did not differ in the expression of the measured genes involved in the innate immune system in the basal ileal or colonic tissues (P > 0.10). Interestingly, there was an interaction between RFI and LPS for the cytokines IL-8, IL-1, IL-6, TNF-α, Interferon-γ (IFN-γ) and SOCS3, with the LRFI group having consistently lower gene expression in the colon following the LPS challenge, compared to the HRFI group. The lower gene expression of SOCS and cytokines following an ex vivo LPS challenge supports the theory that a possible energy saving mechanism exists in the intestinal innate immune response to an immune challenge in more feed efficient pigs.

Risks associated with endotoxins in feed additives produced by fermentation

Increasingly, feed additives for livestock, such as amino acids and vitamins, are being produced by Gram-negative bacteria, particularly Escherichia coli. The potential therefore exists for animals, consumers and workers to be exposed to possibly harmful amounts of endotoxin from these products. The aim of this review was to assess the extent of the risk from endotoxins in feed additives and to calculate how such risk can be assessed from the properties of the additive. Livestock are frequently exposed to a relatively high content of endotoxin in the diet: no additional hazard to livestock would be anticipated if the endotoxin concentration of the feed additive falls in the same range as feedstuffs. Consumer exposure will be unaffected by the consumption of food derived from animals receiving endotoxin-containing feed, because the small concentrations of endotoxin absorbed do not accumulate in edible tissues. In contrast, workers processing a dusty additive may be exposed to hazardous amounts of endotoxin even if the endotoxin concentration of the product is low. A calculation method is proposed to compare the potential risk to the worker, based on the dusting potential, the endotoxin concentration and technical guidance of the European Food Safety Authority, with national exposure limits.

Whole Blood Transcriptomics Is Relevant to Identify Molecular Changes in Response to Genetic Selection for Feed Efficiency and Nutritional Status in the Pig

The molecular mechanisms underlying feed efficiency need to be better understood to improve animal efficiency, a research priority to support a competitive and sustainable livestock production. This study was undertaken to determine whether pig blood transcriptome was affected by differences in feed efficiency and by ingested nutrients. Growing pigs from two lines divergently selected for residual feed intake (RFI) and fed isoproteic and isocaloric diets contrasted in energy source and nutrients were considered. Between 74 and 132 days of age, pigs (n = 12 by diet and by line) received a regular diet rich in cereals and low in fat (LF) or a diet where cereals where partially substituted by lipids and fibers (HF). At the end of the feeding trial, the total number of white blood cells was not affected by the line or by the diet, whereas the red blood cell number was higher (P<0.001) in low RFI than in high RFI pigs. Analysis of the whole blood transcriptome using a porcine microarray reveals a higher number of probes differentially expressed (DE) between RFI lines than between diets (2,154 versus 92 probes DE, P<0.01). This corresponds to 528 overexpressed genes and 477 underexpressed genes in low RFI pigs compared with high RFI pigs, respectively. Overexpressed genes were predominantly associated with translational elongation. Underexpressed genes were mainly involved in the immune response, regulation of inflammatory response, anti-apoptosis process, and cell organization. These findings suggest that selection for RFI has affected the immune status and defense mechanisms of pigs. Genes DE between diets were mainly related to the immune system and lipid metabolism. Altogether, this study demonstrates the usefulness of the blood transcriptome to identify the main biological processes affected by genetic selection and feeding strategies.

Concentration Dependent Influence of Lipopolysaccharides on Separation of Hoof Explants and Supernatant Lactic Acid Concentration in an Ex Vivo/In Vitro Laminitis Model

Laminitis is one of the most common diseases in horses. It is not only painful for the animal, but also has a significant financial impact on the equine industry. This multifactorial disease affects the connective tissue of the hoof. However, the pathogenesis of laminitis is still not fully understood. Endotoxins, also known as lipopolysaccharides (LPS), and bacterial exotoxins seem to play an important role during the development of laminitis. The aim of our study was to investigate the effect of increasing LPS concentrations (0, 2.5, 5, 10, and 100 μg/mL) on cell viability of isolated epidermal and dermal hoof cells as well as on the tissue integrity of hoof explants. Furthermore, glucose, acetic acid, lactic acid, and propionic acid concentrations in explant supernatants were measured to evaluate the energy metabolism in the hoof tissue. LPS did not exhibit cytotoxic effects on epidermal or dermal cells. Force required to separate LPS treated hoof explants decreased in a concentration dependent manner. Specifically, explants incubated with 10 and 100 μg/mL needed significantly less force to separate compared to control explants. Lactic acid concentrations were significantly decreased in explants incubated with 5, 10, or 100 μg/mL LPS, while glucose, acetic acid and propionic acid concentrations were unaffected by LPS treatment. Our study indicates that LPS has no cytotoxic effect on epidermal and dermal cells isolated from hoof tissue, but impairs integrity of hoof explants. In addition, LPS led to an alteration of the lactic acid production in the lamellar tissue. Since our data highlight that LPS can affect the integrity of the equine hoof tissue in vitro, endotoxins should be further explored for their contribution to facilitate the development of laminitis.

The impact of heat stress on intestinal function and productivity in grow-finish pigs

Heat stress is a physiological condition when animals can no longer regulate their internal euthermic temperature. When livestock such as pigs are subjected to this environmental stress, it can be detrimental to performance, health and well-being, and if severe enough even death. Growing pigs are particularly susceptible to heat stress and one of the major organs first affected by heat stress is the gastrointestinal tract. As a result, reductions in appetite, intestinal function and integrity and increased risk of endotoxemia can modify post-absorptive metabolism and tissue accretion. These changes in intestinal integrity may be a result of altered expression of tight junction proteins, increased circulating endotoxin concentrations and markers of cellular stress (heat shock and hypoxia response), which is evident as early on as 2 h after heat-stress onset. Due to restricted blood flow, the ileum is more severely affected compared with the colon. Interestingly, many of the negative effects of heat stress on intestinal integrity appear to be similar to those observed with pigs reared under reduced nutrient and caloric intakes. Altogether, these depress pig performance and health, and extend days to market. Despite this impact on the gastrointestinal tract, under heat-stress conditions, intestinal glucose transport pathways are upregulated. This review discussed how heat stress (directly and indirectly via reduced feed intake) affects intestinal integrity and how heat stress contributes to decreased growth performance in growing pigs.

Effects of Lactobacillus plantarum 2142 and sodium n-butyrate in lipopolysaccharide-triggered inflammation: comparison of a porcine intestinal epithelial cell line and primary hepatocyte monocultures with a porcine enterohepatic co-culture system

This study was based on our previously developed double-layered enterohepatic co-culture system, composed of nontumorigenic porcine intestinal epithelial cell line (IPEC-J2) and primary culture of porcine hepatocytes. The anti-inflammatory effect of spent culture supernatant of Lactobacillus plantarum 2142 (Lp2142; 13.3%) and sodium n-butyrate (2 mM) was tested on IPEC-J2 and hepatocyte monocultures as well as on the gut-liver co-culture. To mimic inflammation, lipopolysaccharide (LPS; 1 and 10 μg/mL) was applied. Production of IL-8 and IL-6 was measured as a marker of inflammatory responses. The paracellular permeability of the intestinal epithelium was also monitored by fluoresceinisothiocyanate-labeled dextran 4 assay. Significant increase of IL-8 concentration was observed in the IPEC-J2 monoculture (P < 0.01) while the level of IL-6 was not changed following LPS treatment. Concentration of IL-8 and IL-6 was grown significantly in hepatocyte monocultures (P < 0.05 and P < 0.001) as well as in the co-culture after 10 μg/mL LPS treatment (P < 0.001 and P < 0.001). One microgram per milliliter LPS caused elevated IL-8 level in the co-culture (P < 0.001) and in the hepatocyte monoculture (P < 0.01), while it caused increased IL-6 level only in the hepatocytes (P < 0.001). Production of IL-8 was significantly decreased by butyrate in case of 1 μg/mL as well as 10 μg/mL LPS exposure in the co-culture (P < 0.001). Application of butyrate also reduced IL-6 level in the co-culture after 10 μg/mL LPS treatment (P < 0.01). Lactobacillus plantarum 2142 decreased IL-8 level after incubation with 1 μg/mL LPS (P < 0.001), while in case of 10 μg/mL LPS treatment only a marginal lowering in IL-8 (P = 0.064) release was measured. The IL-6 concentration was significantly reduced (P < 0.01 in case of 1 μg/mL LPS treatment) by Lp2142 in the co-culture. Contrarily, the elevated IL-8 and IL-6 level of hepatocytes has not been reduced in case of either butyrate or Lp2142 addition. The enterohepatic co-culture model offers a possibility for fast and reliable screening of new candidates against enteric inflammation, which are of special interest in porcine medicine and health management. According to our results, Lp2142 and butyrate both seem to be effective as anti-inflammatory agents in LPS-triggered inflammatory response, tested in the gut-liver co-culture model.