159 Impact of dietary fiber and carbohydrases on intestinal gene transcription in enterotoxigenic E. coli challenged pigs

This study aimed to evaluate if soluble (10% sugar beet pulp) or insoluble dietary fiber (15% corn DDGS) with or without exogenous carbohydrases protect piglets against enterotoxigenic E. coli (ETEC)-induced changes in gene transcription of markers of intestinal inflammation and barrier integrity. Sixty newly-weaned piglets (BW=6.9 ± 0.1 kg; L337 X Camborough, PIC, Hendersonville, TN) were blocked by initial BW, preselected for F18 ETEC sensitivity and placed in individual pens. Pens were randomly assigned to 1 of 6 treatments (n = 10/trt): non-challenged (NC), ETEC-challenged (PC), PC-fed a soluble fiber diet without (SF-) or with (SF+) carbohydrases (xylanase, β-glucanase, and pectinase), or PC fed an insoluble fiber diet without (IF-) or with carbohydrases (IF+). Pigs were orally inoculated with ETEC or PBS on d 7 post-weaning. Intestinal tissues were collected on d 14 or 15. Data were analyzed using PROC GLIMMIX (SAS 9.4); treatment was a fixed effect and block a random effect. The NC decreased interleukin (IL)-8 and increased claudin-1 (CLDN1; 2.32 vs. 0.96) mRNA abundance in the ileum compared to PC (P < 0.05). The SF- increased ileal CLDN1 mRNA compared to PC (P < 0.05). A trend (P < 0.10) for lower levels of tumor necrosis factor alpha (TNFα) and greater occludin (OCLN) mRNA in the ileum was observed in SF+ compared with PC. The IF+ decreased ileal cluster of differentiation 14 (CD14) mRNA abundance compared to PC (P < 0.05). Greater colonic abundance of zonula occludens (ZO-1) mRNA was observed in NC than PC (P < 0.05). Pigs fed SF+ tended (P = 0.051) to have greater ZO-1 and greater OCLN mRNA abundance than pigs on PC (P < 0.05). Collectively, these data suggest that an ETEC challenge increased markers of gut inflammation and reduced mRNA levels of tight junction proteins. Soluble fiber, regardless of enzyme supplementation, may help improve gut barrier integrity during such a challenge.

374 Metabolic response of pigs to Porcine Reproductive and Respiratory Syndrome virus infection and nutrient restriction

Porcine reproductive and respiratory syndrome (PRRS) virus is one of the most economically significant pig pathogens worldwide. The virus infects pigs at all production stages and significantly reduces the tissue accretion of growing pigs. However, the metabolic explanation for these reductions in tissue accretion remain poorly defined. Additionally, PRRS virus infection is often accompanied by reductions in feed intake, making it difficult to discern which effects are virus versus feed intake driven. To account for this, a pair-fed model was employed to examine the effects of PRRS infection and nutrient restriction on skeletal muscle and liver metabolism. Forty-eight pigs were randomly selected (11.34 ± 1.54 kg BW) and allotted to 3 treatments (n = 16 pigs/treatment): 1) PRRS naïve, ad libitum fed (Ad), 2) PRRS-inoculated, ad libitum fed (PRRS+), and 3) PRRS naïve, pair-fed to the PRRS-inoculated pigs’ daily feed intake (PF). At dpi 10 and dpi 17, 8 pigs per treatment were euthanized and tissues collected. Tissues were assayed for markers of proteolysis [longissimus skeletal muscle (LM) only], oxidative stress (LM only), and glycogen levels (LM and liver). Markers of LM proteolysis (calpain, 20s proteasome, caspase 3/7 activities) and mitochondrial reactive oxygen species production did not differ (P > 0.10) between treatment groups at either timepoint. Liver glycogen stores were reduced (P < 0.001) in PRRS+ pigs compared with both Ad and PF pigs, which did not differ from each other. Muscle glycogen did not differ (P > 0.10) between treatment groups. However, liver glycogen stores were completely depleted due to PRRS+, but not pair-feeding, indicating that liver glycogen stores and glucose are preferentially utilized by pigs to produce and support immune components. These data suggest that even under severe viral challenge and feed restriction, the pig does not upregulate LM proteolysis to re-allocate nutrients to fuel the immune response.

130 Young Scholar Presentation: Can exogenous carbohydrase supplementation to higher-fiber diets improve gut function, microbiota, and growth performance of weaned pigs?

There is increasing interest in feeding higher-fiber coproducts to weaned pigs due to their potential benefits on gut function and microbiota. However, young pigs are not efficient at utilizing fibrous coproducts. Exogenous carbohydrases can be used to improve nutrient utilization and growth of pigs fed higher levels of coproducts. Previous results regarding the impact of carbohydrases on performance in pigs have been inconsistent, thus a better understanding of associated mechanisms is needed. Using 460 weaned pigs (6.4 ± 0.1 kg), our first study showed that a carbohydrase enzyme blend (EB) improved ADG of weaned pigs fed higher-fiber diets (with added DDGS and wheat middlings) over a 28-d experimental period (P < 0.05). Pigs fed EB-supplemented diets had lower urinary lactulose:mannitol ratio, decreased plasma IL-8 concentration, and greater ileal CLDN3 (claudin 3) mRNA abundance, compared with those fed diets without EB (P < 0.05). These changes may partly explain the improved growth, providing mode of action evidence for carbohydrase in improving performance of weaned pigs. Carbohydrases may also exert prebiotic effects through release of oligosaccharides from fiber degradation. Thus, carbohydrases and dietary fiber may improve disease resilience of young pigs against bacterial infections, for example, enterotoxigenic Escherichia coli (ETEC) induced post-weaning diarrhea. Our second study evaluated the impact of soluble versus insoluble fiber with or without carbohydrases in newly weaned pigs (n = 60; 6.9 ± 0.07 kg) challenged with F18 ETEC. A diet containing a soluble and highly fermentable fiber from sugar beet pulp with added carbohydrases improved (P < 0.05) ADG, tended to increase (P < 0.10) ileal OCLN (occludin) mRNA, increased (P < 0.05) colonic OCLN mRNA, and tended to decrease (P < 0.10) ileal Escherichia-Shigella compared with ETEC-challenged control. Collectively, appropriate use of exogenous carbohydrases in higher-fiber diets (with the right type and amount of enzyme substrate) is promising in improving gut health and growth performance in weaned pigs.

364 Impact of porcine reproductive and respiratory syndrome virus challenge and deoxynivalenol on intestinal integrity and nutrient transport

Porcine reproductive and respiratory syndrome (PRRS) virus infections and mycotoxin contaminated feedstuffs are two common issues facing the pork industry as both act, independently, to antagonize pig intestinal function, growth performance, and health. However, the combined impact of PRRS and mycotoxin exposure on pig intestinal health and function has not been investigated. Therefore, the objective of this experiment was to examine the impact of the mycotoxin deoxynivalenol (DON) on the intestinal integrity and function of PRRS infected pigs, employing an ex vivo model. Jejunum samples were collected from PRRS naïve (control; n = 6) and 21 day post inoculated PRRS virus infected (n = 8) gilts (10 weeks of age). In duplicate, explants were mounted into modified Ussing Chambers and incubated with or without 25 mM DON for 45 minutes prior to assessment of transepithelial resistance (TER), mucosal to serosal macromolecule (FD4) flux, and active glucose and glutamine transport. Data were analyzed using the mixed model procedure of SAS and a split plot design to examine the fixed effects of PRRS, DON, and their interaction. There were no PRRS by DON interactions for any ex vivo parameters assessed. Irrespective of DON, PRRS jejunum segments had decreased TERs (57%, P < 0.001), increased FD4 flux (P = 0.005), and tended to have increased active glucose transport (P = 0.093) compared with uninfected controls. Irrespective of PRRS status, DON increased FD4 flux (113%, P = 0.013), and tended to increase active glucose transport (P = 0.088) compared with jejunal explants not treated with DON. However, TERs and active glutamine transport did not differ due to DON treatment. Taken together, these data highlight the impacts that viral health challenge and mycotoxin contamination have on aspects of intestinal integrity and function. However, it does not appear that PRRS challenged pigs are more sensitive to the effects of DON than their healthy counterparts.

PSVII-5 Zinc overload in weaned pigs: tissue accumulation, pathology, and growth impacts

Pharmacological concentrations of zinc (Zn, 2000-3000 ppm) are commonly fed to nursery pigs. However, diet manufacturing errors can result in supra-pharmacological concentrations of Zn (>4000 ppm) being fed. Clinical and phenotypic data reflective of Zn associated morbidity in modern genotype pigs are poorly defined. Therefore, the study objective was to characterize the effect of dietary Zn overload on nursery pig performance, body mineral concentrations and pathologic changes. Fifty-five 21 d old weaned pigs (4.50 ± 0.2 kg BW) were randomly assigned to one of five Zn diet treatments for 21 d. Diets included: 1) Control no additional Zn (NC), 2) 6000 ppm Zn for 21 d (Zn6), 3) 6000 ppm Zn for 7 d plus 4000 ppm Zn for 14 d (Zn64), 4) 3000 ppm Zn for 7 d and no additional Zn for 14 d (Zn3), and 5) 3000 ppm Zn for 7 d plus 2000 ppm for 14 d (Zn32). All pigs were bled and weighed at d 0, 7 and 21, and ADFI and G:F were determined for the overall 21 d test period. Thereafter, all pigs were necropsied for histopathology and serum, tissue and feed trace mineral concentrations were determined. Data were analyzed by one-way ANOVA with Tukey-Kramer adjustment in JMP. Overall pig ADG, ADFI and G:F was not statistically different between treatments. Feeding greater than 6000 ppm Zn increased pancreatic Zn concentrations compared to other groups (P < 0.001), and pancreatic apoptosis was more frequent in pigs fed supra-pharmacological levels of Zn (P < 0.0001). Hepatic and serum Zn levels were highest in diet 2 and 3 pigs compared to the other diets (P < 0.0001 and P = 0.0003 respectively) and only pigs from these treatments had serum Zn >2.0 ppm or hepatic Zn >500 ppm. Accordingly, these mineral levels should warrant further feed analysis if expected inclusion rates are 3,000 ppm Zn or less.

PSIV-18 Effect of sub-therapeutic antibiotics and pharmacological zinc oxide on nursery pig performance and intestinal integrity and function

The objective of this study was to evaluate the impact of sub-therapeutic chlortetracycline (CTC) and pharmacological zinc oxide on nursery pig performance and intestinal integrity and function. Twenty-four newly weaned pigs (4.51 ± 0.21 kg BW) were randomly assigned to one of three dietary treatments for 21 d (n = 8/treatment): 1) Control diet (NC), 2) NC + Zinc oxide at 3000 ppm for 7 d followed by 2000 ppm for 14 d (ZnO), and 3) NC + 40 ppm CTC for 21 d (sCTC). Pig ADG, ADFI, and G:F were determined for the overall 21 d test period. At d 21, all pigs were euthanized for tissue collection. Jejunum and ileum ex vivo transepithelial resistance (TER), macromolecule (FD4) flux, and active glucose and glutamine transport were assessed in modified Ussing Chambers. Additionally, jejunum brush border enzyme and Na+/K+ ATPase activities were determined. Morphology and T-cell abundance were determined in all ileum sections by H&E staining and immunohistochemistry, respectively. Compared to the NC, sCTC and ZnO increased ADG (0.14, 0.20 and 0.23 kg/d, respectively, P = 0.020). Overall ADFI was increased by 150% due to sCTC compared to the NC and ZnO pigs (P < 0.05). G:F was increased due to ZnO and sCTC compared to the NC (0.82, 0.63 and 0.47, respectively, P < 0.01). Jejunum and ileum ex vivo function and integrity did not differ. Ileal villus height was increased in the NC compared to sCTC treatment (P < 0.01), but not different from the ZnO treatment. In the ileum, total T-cell number per unit area was significantly lower in the ZnO segments compared to sCTC and NC (0.95, 2.29 and 2.59 count per μm2, respectively, P = 0.05). These data indicate that ZnO and sCTC improved pig performance but did not directly alter small intestinal integrity and function. However, mucosal T cell abundance was altered.

194 Performance and febrile response of nursery pigs to a porcine reproductive and respiratory syndrome virus challenge

Porcine reproductive and respiratory syndrome (PRRS) virus is an economically significant pathogen that antagonizes production in all stages of the swine industry. In nursery pigs, it increases the risk of mortality and reduces growth performance parameters. Thus, the objective of this study was to further understand how PRRS virus infection and its associated viremia and serology levels related to febrile response and performance in nursery pigs. Over two replicates, 37 three-week post-weaned PRRS naïve gilts (11.2 ± 2.56 kg BW) were randomly assigned to one of two treatments: Control (CON, n = 16) or PRRS virus-inoculated (PRRS+, n = 21). All pigs were housed individually in a BSL2 facility for the 21 d test period. PRRS serology, BW, ADG, ADFI, and G:F were determined at 0, 7, 14 and 21 days post inoculation (dpi). Core body temperatures were collected daily using a biosensor microchip. Data was analyzed using mixed procedure of SAS with dpi as a repeated effect and CON or PRRS+ as a treatment effect. Treatment, dpi and their interactions were assessed. As expected, viremia and antibody titers in PRRS+ pigs were significantly different compared to CON pigs, which remained negative (P < 0.001). The lowest PRRS Ct was observed at dpi 7, while antibody titers were highest between dpi 14 to 21 (P < 0.001). Compared with the CON, PRRS+ reduced BW gains by 17, 33 and 42% at dpi 7, 14 and 21 respectively (P < 0.001). The PRRS challenge also reduced ADFI by 30, 67 and 68% at dpi 7, 14 and 21 respectively, compared to CON (P < 0.001). The febrile response in the PRRS+ pigs peaked between dpi 7 and 14 then returned to CON baseline level by dpi 21 (P < 0.001). Overall, PRRS virus challenge induced a sustained febrile response that contributes to the attenuated performance of nursery pigs.

57 Impact of weaning stress, disease, and diet on pig performance, intestinal function and integrity

Inevitably, pigs will experience stressors that antagonize lean tissue accretion, appetite, and feed conversion. Depending on the production system and age of the pig, these stressors commonly include weaning transition, diet changes, vaccination, enteric and respiratory pathogen challenges, activation of the HPA axis, and social stress. Additionally, the morbidity and mortality that accompany these stressors may be exacerbated by the illegalization of sub-therapeutic antibiotic use for growth promotion (AGPs) by the Veterinary Feed Directive. However, morbidity and mortality may also be mitigated by diet ingredients via direct and indirect modes of action on gastrointestinal health and function. The gastrointestinal tract has the vital but conflicting functions of nutrient and water absorption, while simultaneously regulating host mucosal defenses against noxious luminal contents such as microorganisms and their toxins. This puts the gastrointestinal tract epithelium and splenic tissue at the front line of nutrition, growth, and health of the pig in the new age of antimicrobial resistance concerns. As part of the body’s splanchnic tissues, the gastrointestinal tract is very metabolically active and has high utilization of luminal nutrients and energy. This utilization or “first pass metabolism” by intestinal epithelial and lamina propria cells can be a major determinant of the systemic or post-absorptive availability of glucose, essential and non-essential amino acids, and short and long chain fatty acids. This makes the gastrointestinal tract critically important to the growth and health of livestock and avian species. This paper will discuss the physiological impact of various stress challenges and nutrition on pig performance, gastrointestinal function and integrity.

198 An in vivo model to investigate the effects of host stress and Salmonella typhimurium infection on nursery pigs

In animals, the sympathoadrenal and hypothalamic-pituitary-adrenal axis release chemicals that can act on and alter host microbiota. Therefore, the objectives of this study were to investigate if host stress (via adrenocorticotropin and catecholamine challenge) would increase the severity of a salmonella typhimurium infection. A total of 32 nursery pigs (7.6 ± 1.5 kg BW) were selected and split into treatment groups using a 2 x 2 factorial design to examine the impacts of stress hormone challenge, S. Typhimurium challenge, and their interaction. The resulting treatment groups (n = 8 pigs/treatment) were: 1) non-challenged controls (CON), 2) stress challenged, S. Typhimurium negative (CAT), 3) stress challenge negative, S. Typhimurium challenged (SAL), and 4) stress challenged, S. Typhimurium challenged (CAT+SAL). On days post inoculation (dpi) -1, the stress challenge was initiated and continued daily until dpi 4. The stress challenge consisted of an adrenocorticotropin injection (intramuscular, 0.2 IU/kg BW), a norepinephrine injection (intramuscular, 45 μg/kg BW), and an oral drench of L-DOPA (50 mg/kg BW). On dpi 0, pigs were inoculated with a field strain of S. Typhimurium. On dpi 5, plasma was collected and all pigs were necropsied for tissue collection. Plasma and colon samples were assayed for cortisol, norepinephrine, epinephrine, and dopamine. Colon contents and the ileocecal lymph node were cultured for S. Typhimurium. At dpi 5, plasma norepinephrine, epinephrine, and dopamine concentrations were increased (P < 0.05) and plasma cortisol tended to be increased (P = 0.077) due to stress challenge. However, only colon dopamine concentrations were increased (P = 0.050) due to stress challenge. Further, CAT+SAL pigs didn’t have increased colon colonization of S. typhimurium or increased translocation to the ileocecal lymph node compared with SAL pigs. This suggests that host driven stress may not specifically exacerbate the severity of an S. Typhimurium infection.

Dietary Resistant Potato Starch Alters Intestinal Microbial Communities and Their Metabolites, and Markers of Immune Regulation and Barrier Function in Swine

Interactions between diet, the microbiota, and the host set the ecological conditions in the gut and have broad implications for health. Prebiotics are dietary compounds that may shift conditions toward health by promoting the growth of beneficial microbes that produce metabolites capable of modulating host cells. This study's objective was to assess how a dietary prebiotic could impact host tissues via modulation of the intestinal microbiota. Pigs fed a diet amended with 5% resistant potato starch (RPS) exhibited alterations associated with gut health relative to swine fed an unamended control diet (CON). RPS intake increased abundances of anaerobic Clostridia in feces and several tissues, as well as intestinal concentrations of butyrate. Functional gene amplicons suggested bacteria similar to Anaerostipes hadrus were stimulated by RPS intake. The CON treatment exhibited increased abundances of several genera of Proteobacteria (which utilize respiratory metabolisms) in several intestinal locations. RPS intake increased the abundance of regulatory T cells in the cecum, but not periphery, and cecal immune status alterations were indicative of enhanced mucosal defenses. A network analysis of host and microbial changes in the cecum revealed that regulatory T cells positively correlated with butyrate concentration, luminal IgA concentration, expression of IL-6 and DEF1B, and several mucosa-associated bacterial taxa. Thus, the administration of RPS modulated the microbiota and host immune status, altering markers of cecal barrier function and immunological tolerance, and suggesting a reduced niche for bacterial respiration.

Zinc overload in weaned pigs: tissue accumulation, pathology, and growth impacts

Zinc oxide (ZnO) is commonly fed to pigs at pharmacologic concentrations (2,000-3,000 ppm) for the first 3 wk post-weaning to increase growth and reduce enteric bacterial disease. The safety of this high-dose treatment is assumed based upon lower bioavailability of ZnO compared to other common forms of Zn in feed; however, limited data are available regarding the specific serum and tissue concentrations of Zn expected in animals experiencing overload following feeding of excessive ZnO. Fifty-five 3-wk-old pigs were divided into 5 groups receiving various concentrations of ZnO (0-6,000 ppm) for 3 wk. Pigs receiving 6,000 ppm ZnO had higher mean pancreatic Zn concentrations (p < 0.001) compared to other treatments, and higher pancreatic Zn concentrations were associated with pancreatic acinar cell apoptosis (p < 0.0001). Hepatic Zn concentrations were highest for pigs receiving 6,000 ppm ZnO (mean ± SEM; 729 ± 264 ppm) and significantly higher than all other groups (p < 0.0001), with controls having concentrations <60 ppm. Similarly, serum Zn was highest in pigs receiving 6,000 ppm ZnO (4.81 ± 2.31 ppm) and significantly higher than all groups (controls, <1 ppm). Additionally, as pigs became overloaded with Zn, there were significant reductions in serum Cu and both serum and hepatic Se. Hepatic and serum Zn concentrations >500 ppm and >2 ppm, respectively, are indicative of Zn overload, and dietary trace mineral analysis is warranted if expected inclusion rates are ≤3,000 ppm ZnO.

Mycoplasma hyopneumoniae-Lawsonia intracellularis dual challenge modulates intestinal integrity and function1

Lawsonia intracellularis (LI) and Mycoplasma hyopneumoniae (Mh) are 2 globally distributed pathogens that cause significant morbidity and mortality in grow-finish pigs. However, mechanisms that reduce growth and feed efficiency during LI and Mh infection are poorly defined. We hypothesized that reductions in performance are partially due to declines in intestinal function and integrity; thus, this study aimed to evaluate intestinal function and integrity of pigs during a 21-d Mh and LI dual challenge (MhLI). Littermate pairs of barrows (48.1 ± 6.7 kg BW) were selected; 1 pig from each pair was assigned to either MhLI challenge or nonchallenge treatments (n = 12). Pigs were individually housed, fed a corn-soybean diet, and allowed to acclimate for 21 d prior to inoculation. On days postinoculation (dpi) 0, MhLI pigs were dual inoculated with LI and Mh. On dpi 21, all pigs were euthanized for ileal and colon tissue collection. Formalin-fixed tissues were clinically scored and morphology analyzed, frozen tissues assayed for digestive enzyme activities, and fresh tissues mounted into modified Ussing Chambers to assess active nutrient transport, barrier integrity, and bacterial translocation. Data were analyzed using the Mixed Procedure of SAS with treatment as a fixed effect, age and start BW as covariates, and litter as a random effect. Compared with controls, MhLI pigs had decreased ADG (38%, P < 0.001), ADFI (25%, P < 0.001), and G:F (19%, P = 0.012). The MhLI dual challenge did not alter ileum morphology or transepithelial resistance (P > 0.10); however, ex vivo mucosal to serosal translocation of S. Typhimurium in the colon was increased (60%, P = 0.003) in MhLI pigs compared with controls. Additionally, MhLI pigs had increased ileal glucose transport (30%, P = 0.05) and decreased sucrase activity (30%, P = 0.049) compared with controls. This MhLI challenge antagonized intestinal function and integrity, and this may be a contributing factor to reduced pig performance.

A soluble and highly fermentable dietary fiber with carbohydrases improved gut barrier integrity markers and growth performance in F18 ETEC challenged pigs1

This study aimed to evaluate the effects of a source of dietary soluble (SF) and insoluble fiber (IF) without or with exogenous carbohydrases (xylanase, β-glucanase, and pectinase) on diarrhea incidence, selected immune responses, and growth performance in enterotoxigenic Escherichia coli (ETEC)-challenged pigs. Sixty weaned pigs (6.9 ± 0.1 kg BW, ~23 d of age) were blocked by initial BW and placed in individual pens. Pens were randomly assigned to one of six treatments (n = 10 per treatment), including a nonchallenged control (NC), a positive challenge control (PC), the PC + a soluble fiber diet (10% sugar beet pulp) without (SF-) or with carbohydrases (SF+), and PC + an IF diet (15% corn distillers dried grains with solubles) without (IF-) or with carbohydrases (IF+). The control diet was primarily based on corn and soybean meal with 13.5% whey powder. The two sources of fiber were added at the expense of cornstarch in the control diet. Pigs were orally inoculated with 6 mL hemolytic F18 ETEC (~3.5 × 109 cfu/mL) or sham infected with 6 mL phosphate-buffered saline on day 7 (0 d postinoculation, dpi) postweaning. All ETEC challenged pigs were confirmed to be genetically susceptible to F18 ETEC. Pigs had free access to feed and water throughout the 14-d trial. Pig BW and feed intake were recorded on dpi -7, 0, and 7 or 8. Fecal swabs were collected on dpi -7, 0, 1, 2, 3, 5, and 7 or 8 to evaluate hemolytic E. coli shedding. Fecal score was visually ranked daily postchallenge to evaluate diarrhea incidence. Blood samples were collected on dpi -1, 3, and 7 or 8 at necropsy and intestinal tissues were collected at necropsy. Pigs on PC had lower dpi 1 to 7 ADG and ADFI than those on NC (P < 0.05). Compared with PC pigs, SF+ pigs had greater ADG during both pre- and postchallenge period (P < 0.05). The IF- increased postchallenge diarrhea incidence compared with PC (P < 0.05). Pigs on SF- had lower ileal E. coli attachment than PC (P < 0.05). The SF+ reduced haptoglobin and IF+ reduced C-reactive protein on dpi 3 compared with PC (P < 0.05). Compared with PC pigs, SF+ pigs tended to have lower ileal tumor necrosis factor alpha and greater ileal occludin (OCLN) mRNA (P < 0.10) and had greater (P < 0.05) colonic OCLN mRNA levels. Collectively, IF- increased incidence of diarrhea and fecal E. coli shedding compared with PC. The SF+ pigs had improved growth compared with PC pigs, likely due in part to a reduction in inflammatory intermediates.

Exogenous carbohydrases added to a starter diet reduced markers of systemic immune activation and decreased Lactobacillus in weaned pigs1

Although the impact of carbohydrases on performance and nutrient utilization has been well studied, their effects on immune status and intestinal microbiota are less known in pigs. This study aimed to evaluate the impact of xylanase (X) and a carbohydrase enzyme blend (EB; cellulase, ß-glucanase, and xylanase) on the immune profile of the intestine and peripheral system as well as intestinal microbes and microbial metabolites of weaned pigs fed higher fiber diets. Pigs (n = 460; 6.43 ± 0.06 kg BW; F25 × 6.0 Genetiporc) were blocked by initial BW. Pens (n = 48; 12 per treatment; 9 or 10 pigs per pen) were randomly assigned to 1 of 4 dietary treatments, including a higher fiber control diet (CON) and the CON supplemented with 0.01% X, 0.01% EB, or both enzymes (X + EB), arranged in a 2 × 2 factorial. The diets were based on corn, soybean meal, corn distillers dried grains with solubles, and wheat middlings. After 7-d adaptation to the environment, pigs were fed experimental diets ad libitum for 28 d. Blood samples were collected from the same pig within each pen on days 0, 7, 14, and 28. Intestinal tissues and digesta were collected on day 28. Bacteria 16S rRNA gene copy numbers were quantified using qPCR. The mRNA levels of colonic IL-17, occludin (OCLN), and claudin 3 (CLDN3) were greater in pigs fed diets with X + EB, but not X or EB, compared with those fed CON (P < 0.05). The EB in the diet reduced plasma IL-8 over the 28-d trial compared with diets without EB (P < 0.05). There was an X × EB interaction on plasma tumor necrosis factor α and IL-1ß (P < 0.05); their levels were decreased when X and EB were added together, but not individually, compared with CON. The EB decreased cecal propionate, butyrate, and total volatile fatty acids (P < 0.05). Pigs fed X had lower ileal Lactobacillus and greater ileal and cecal Enterobacteriaceae compared with those fed unsupplemented diets (P < 0.05). The EB decreased Lactobacillus (P < 0.05) and tended to decrease (P = 0.065) Enterobacteriaceae in the colon compared with diets without EB. In conclusion, the addition of X and EB together decreased systemic markers of immune activation, potentially diverting energy and nutrients towards growth. The EB reduced colonic Lactobacillus and cecal total volatile fatty acids, probably due to improved prececal fiber and starch degradation and thus reduced substrate availability in the large intestine. These data corroborated previously observed enhanced growth in pigs fed EB-supplemented diets.

Evaluation of the protective effects of zinc butyrate in IPEC-J2 cells and grower pigs under heat stress

Heat stress (HS) is a major environmental stressor primarily affecting swine performance through negative effects on intestinal health. Zinc and butyric acid supplementation help maintain intestinal integrity and barrier function, and has been shown to be beneficial to swine during stress conditions. We tested a novel formulation of zinc butyrate (ZnB) to study whether it has protective effects toward swine using pig intestinal epithelial cells (IPEC-J2) and in a grower swine HS trial. IPEC-J2 cells were grown either under an inflammatory challenge (Escherichia coli lipopolysaccharide) or HS (41.5 °C for 48 h) using Transwell plates. The tight junction integrity of the cells under various treatments, including ZnB, zinc sulfate, and calcium butyrate, was followed over a period of 36 to 48 h by measuring transepithelial electrical resistance (TER). During inflammatory challenge, ZnB-treated cells had the greatest TER (P < 0.05) at 36 h. When the cells were exposed to HS at 41.5 °C, ZnB-treated cells had similar TER to the cells incubated at 37.0 °C, indicating significant protection against HS. In the swine trial (two dietary treatments, control and an encapsulated form of 40% zinc butyrate [E-ZnB] in hydrogenated palm oil pearls, 12 pigs per treatment), grower gilts (35 ± 1 kg) were supplemented with E-ZnB for 24 d before being subjected to biphasic HS for 7 d, 30 to 32 °C for 8 h and 28 °C for 16 h, for a total duration of 56 h of HS. At the end of the HS phase, half the pigs were euthanized from each treatment (n = 6 per treatment), and growth performance was calculated. During the HS phase, average daily gain (ADG; 0.53 vs. 0.79 kg) and gain-to-feed ratio (G:F; 0.33 vs. 0.43) were greater in the E-ZnB group (P < 0.05). Although in vivo intestinal permeability increased during the HS phase (P < 0.05), no differences were observed in the present study for the intestinal health parameters measured including TER, villus height:crypt depth ratio, and in vivo and ex vivo intestinal permeability between the two treatment groups. In conclusion, results presented here demonstrate that E-ZnB supplementation during HS improves ADG and G:F in grower pigs. Although we could not measure any differences, the mode of action of butyric acid and zinc suggests that the performance improvements are related to improved intestinal health.

Impact of Brachyspira hyodysenteriae on intestinal amino acid digestibility and endogenous amino acid losses in pigs

Brachyspira hyodysenteriae (Bhyo) induces mucohemorrhagic diarrhea in pigs and is an economically significant disease worldwide. Our objectives were to determine the impact of Bhyo on apparent total tract digestibility (ATTD), ileal digestibility (AID), and ileal basal endogenous losses (BEL) in grower pigs. In addition, we assessed the effect of Bhyo on hindgut disappearance of DM, N, and GE. Thirty-two Bhyo negative gilts (38.6 ± 0.70 kg BW) were fitted with a T-cannula in the distal ileum and individually penned. In replicates 1 and 2, pigs were fed a complete diet (7 Bhyo-, 10 Bhyo+ pigs) or nitrogen-free diet (NFD; 4 Bhyo-, 11 Bhyo+ pigs), respectively. Across multiple rooms, the 21 Bhyo+ pigs (62.6 ± 1.39 kg BW) were inoculated with Bhyo on day post inoculation (dpi) 0, and the 11 Bhyo- pigs were sham inoculated. Feces were collected from 9 to 11 dpi and ileal digesta collected from 12 to 13 dpi. All pigs were euthanized at 14 to 15 dpi and intestinal tract pathology assessed. Within the complete diet and NFD treatments, data were analyzed to determine pathogen effects. All Bhyo- pigs remained Bhyo negative, and 5 Bhyo+ pigs in each replicate were confirmed Bhyo positive within 9 dpi. Infection with Bhyo reduced ATTD of DM, N, and GE and increased AID of Gly (P < 0.05). No other AA AID differences were observed. Only BEL of Pro was reduced (P < 0.05) while Arg, Trp, and Gly tended (P < 0.10) to be reduced in Bhyo+ pigs. When calculated from AID and BEL, Bhyo infection reduced standardized ileal digestibility (SID) of N, Arg, Lys, Ala, Gly, Pro, and Ser (P < 0.05) and tended to reduce Thr SID (P = 0.09). In the hindgut of Bhyo+ pigs, there was generally an appearance of nutrients rather than disappearance. In Bhyo+ pigs fed a complete diet, hindgut appearance of N and GE were increased (P < 0.05) by 58 and nine-fold, respectively, and DM tended to be increased two-fold (P = 0.06). Similarly, in NFD fed pigs, hindgut appearance of N and GE was increased by 172% and 162%, respectively, although high variability led to no significance. Altogether, Bhyo infection decreases ATTD but has minimal impact on AID of AA, when corrected for BEL, SID of N, Arg, Lys and some nonessential AA are specifically reduced. Unexpectedly, BEL of several AA involved in mucin production were unaffected by Bhyo infection. This may suggest an increased need for specific AA and energy during a Bhyo challenge.

A dietary carbohydrase blend improved intestinal barrier function and growth rate in weaned pigs fed higher fiber diets

The objective of this study was to evaluate the effects of dietary xylanase (X) and a carbohydrase enzyme blend (EB: cellulase, β-glucanase, and xylanase) on nutrient digestibility, intestinal barrier integrity, inflammatory status, and growth performance in weaned piglets fed higher fiber diets. A total of 460 pigs (6.43 ± 0.06 kg BW; F25 × 6.0 Genetiporc) were blocked by initial BW and pens (n = 12 per treatment) were randomly assigned to 1 of 4 dietary treatments. The diets included a higher fiber unsupplemented control diet (CON) and the CON supplemented with 0.01% X, 0.01% EB, or both enzymes, arranged in a 2 × 2 factorial. The diets were based on corn, soybean meal, corn distillers dried grains with solubles (DDGS), and wheat middlings. Pigs had 7 d to adapt to the environment and consumed the same commercial diet. Pigs were fed the experimental diets for 28 d with free access to feed and water. Body weight and feed disappearance were recorded weekly. One pig with BW closest to the pen average from each pen was selected and moved to metabolism crates on day 16 and intragastric gavaged a solution of lactulose and mannitol on day 22 followed by 12-h urine collection. Feces were collected from day 23 to 25. Intestinal tissues and mucosal scrapings were collected on day 28. Data were analyzed using PROC MIXED of SAS (9.4). Xylanase, EB, and their interaction were fixed effects and block was a random effect. The EB, but not X, increased pig BW and improved ADG over 28 d (P < 0.05). Neither carbohydrase impacted ADFI, G:F, or apparent total tract digestibility (ATTD) of DM, GE, or CP. The EB improved ATTD of ADF (32.45 vs. 26.57%; P < 0.01), but had no effect on NDF. Unexpectedly, X reduced ATTD of NDF and ADF (P < 0.01). The EB reduced urinary lactulose:mannitol and increased ileal claudin-3 mRNA abundance (P < 0.05), indicating improved small intestinal barrier integrity. There was a X × EB interaction on ileal secretory immunoglobulin A (sIgA) concentration (P < 0.05); in the absence of X, EB decreased sIgA compared to CON, but this effect disappeared in the presence of X. The EB also reduced ileal IL-22 mRNA abundance (P < 0.05), probably indicating decreased immune activation. In conclusion, EB but not X enhanced growth rate of weaned pigs fed higher fiber diets, which may be partly explained by the improved small intestinal barrier integrity and reduced immune activation, rather than improvement in nutrient digestibility.

Increased lysine: metabolizable energy ratio improves grower pig performance during a porcine reproductive and respiratory syndrome virus challenge

Porcine reproductive and respiratory syndrome virus (PRRSV) reduces grower pig performance. The amino acid (AA) requirements and lysine:metabolizable energy ratio (Lys:ME) of health-challenged pigs for optimum performance are poorly understood. Two experiments were conducted to evaluate the effect of increasing standardized ileal digestible (SID) Lys:ME (g SID Lys per Mcal ME) on growth performance during a PRRSV challenge. In Exp. 1, a total of 379 barrows (51.3 ± 0.3 kg body weight [BW]) were allotted to one of six diets (1.87 to 3.41 Lys:ME) for a 35-d growth study. In Exp. 2, a total of 389 barrows (29.2 ± 0.23 kg BW) were allotted to one of six diets (2.39 to 3.91 Lys:ME) for a 49-d growth study. These isocaloric diets represented 80% to 130% of National Research Council (NRC) SID Lys requirement. For each experiment, pigs were randomly allotted across two barns of 24 pens each with seven to nine pigs per pen (four pens per diet per health status). On day 0, one barn was inoculated with live PRRSV, one barn sham inoculated (control), and all pigs were started on experimental diets. Pen growth performance and feed intake were recorded weekly and gain-to-feed ratio (G:F) was calculated. Breakpoint analysis was used to determine the Lys:ME that maximized average daily gain (ADG) and G:F over the 35 or 49-d test periods for Exp. 1 and 2, respectively. In Exp. 1, increasing Lys:ME increased ADG (quadratic P = 0.01) and G:F (linear and quadratic P = 0.04) in control pigs over 35 d. In PRRSV-infected pigs, ADG and G:F increased linearly with increasing Lys:ME (P < 0.01). The Lys:ME for optimum ADG and G:F during PRRSV challenge was 2.83 and 3.17, respectively, compared to 2.24 and 2.83, respectively, in control pigs using a one-slope broken-line model. In Exp. 2, pigs in the control barn became naturally infected after 21 days post inoculation. Before infection, ADG and G:F increased with increasing Lys:ME in control and PRRSV-infected pigs (linear and quadratic P < 0.05), and optimum ADG and G:F were achieved at 3.02 and 2.92 Lys:ME, respectively, in PRRSV-infected pigs compared to 2.82 and 3.22 Lys:ME, respectively, in control pigs. Over the 49-d period, increasing Lys:ME improved ADG (P < 0.01, linear and quadratic) and G:F (linear P < 0.01) in naturally infected pigs. The response was similar in experimental infection for ADG (P < 0.01, linear and quadratic) and G:F (linear P = 0.01). The optimum ratio for ADG (2.86 vs. 3.12 Lys:ME) and G:F (3.18 vs. 3.08 Lys:ME) were similar between natural and experimental infection. In summary, increasing Lys:ME by 10% to 20% above NRC requirements improved performance and feed efficiency during an experimental and natural PRRSV challenge.

The effects of group size and subtherapeutic antibiotic alternatives on growth performance and morbidity of nursery pigs: a model for feed additive evaluation

The objectives of this experiment were to evaluate the effects of alternatives to antibiotic growth promoters (AGP), two group sizes, and their interaction on nursery pig performance to serve as a model for future AGP alternative studies. A 41-d experiment was conducted in a commercial wean-to-finish barn; 1,300 piglets weaned at 21 d of age (weaned 2 or 4 d prior to experiment; 6.14 ± 0.18 kg BW; PIC 1050 sows and multiple sire lines) were blocked by sire, sex, and weaning date, then assigned to eight treatments: four dietary treatments each evaluated across two group sizes. The four dietary treatments were: negative control (NC), positive control (PC; NC + in-feed antibiotics), zinc oxide plus a dietary acidifier (blend of fumaric, citric, lactic, and phosphoric acid) (ZA; NC + ZnO + acid), and a Bacillus-based direct-fed-microbial (DFM) plus resistant potato starch (RS) (DR; NC + DFM + RS). The two group sizes were 31 or 11 pigs/pen; floor space was modified so area/pig was equal between the group sizes (0.42 m2/pig). There were 7 pens/diet with 11 pigs/pen and 8 pens/diet with 31 pigs/pen. Data were analyzed as a randomized complete block design with pen as the experimental unit. Diagnostic assessment of oral fluids, serum, and tissue samples was used to characterize health status. Pigs experienced natural challenges of acute diarrhea and septicemia in week 1 and porcine reproductive and respiratory syndrome virus (PRRSV) in weeks 4-6. There was a significant interaction between diet and group size for ADG (P = 0.012). PC increased ADG in large and small groups (P < 0.05) and ZA increased ADG only in large groups (P < 0.05). Small groups had improved ADG compared to large groups when fed NC or DR diets (P < 0.05). Similarly, PC increased ADFI (P < 0.05). Compared to NC, ZA improved ADFI in large groups only (P < 0.05; diet × group size: P = 0.015). Pigs fed PC had greater G:F than NC (P < 0.05), and small groups had greater G:F than large groups (P < 0.05). There was no effect of ZA or DR on G:F. Pigs fed PC required fewer individual medical treatments than NC and pigs fed ZA were intermediate (P = 0.024). More pigs were removed from large than small groups (P = 0.049), and there was no effect of diet on removals (P > 0.10). In conclusion, careful study design, protocol implementation, sample collection, and recording of important information allowed us to characterize the health status of this group of pigs and determine treatment effects on growth performance and morbidity.

Influence of feeding thermally peroxidized soybean oil on oxidative status in growing pigs

The objectives of this study were to determine whether feeding thermally processed peroxidized soybean oil (SO) induces markers of oxidative stress and alters antioxidant status in pig tissue, blood, and urine. Fifty-six barrows (25.3 ± 3.3 kg initial BW) were randomly assigned to dietary treatments containing 10% fresh SO (22.5 °C) or thermally processed SO (45 °C for 288 h, 90 °C for 72 h, or 180 °C for 6 h), each with constant air infusion rate of 15 liters/minute. Multiple indices of lipid peroxidation were measured in the SO including peroxide value (2.0, 96, 145, and 4.0 mEq/kg for 22.5, 45, 90, and 180 °C processed SO, respectively) and p-anisidine value (1.2, 8.4, 261, and 174 for 22.5, 45, 90, and 180 °C processed SO, respectively); along with a multitude of aldehydes. Pigs were individually housed and fed ad libitum for 49 d which included a 5 d period in metabolism crates for the collection of urine and serum for measures of oxidative stress. On day 49, pigs were euthanized to determine liver weight and analyze liver-based oxidative stress markers. Oxidative stress markers included serum, urinary, and liver thiobarbituric acid reactive substances (TBARS), and urinary F2-isoprostanes (ISP) as markers of lipid damage; serum and liver protein carbonyls (PC) as a marker of protein damage; and urinary and liver 8-hydroxy-2'-deoxyguanosine (8-OH-2dG) as a marker of DNA damage. Superoxide dismutase (SOD), and catalase activity (CAT) were measured in liver, glutathione peroxidase activity (GPx) was measured in serum and liver, and ferric reducing antioxidant power (FRAP) was measured in serum and urine as determinants of antioxidant status. Pigs fed 90 °C SO had greater urinary ISP (P = 0.02), while pigs fed the 45 °C SO had elevated urinary TBARS (P = 0.02) in comparison to other treatment groups. Pigs fed 45 °C and 90 °C SO had increased serum PC concentrations (P = 0.01) and pigs fed 90 °C SO had greater (P = 0.01) liver concentration of 8-OH-2dG compared to pigs fed the other SO treatments. Furthermore, pigs fed 90 °C SO had reduced serum GPx activity in comparison to pigs fed fresh SO (P = 0.01). In addition, pigs fed 180 °C SO had increased liver CAT activity (P = 0.01). Liver GPx and SOD or serum and urinary FRAP were not affected by dietary treatment. These results indicate that dietary peroxidized soybean oil induced oxidative stress by increasing serum PC while diminishing serum GPx, increasing urinary ISP and TBARS, and increasing 8-OH-2dG and CAT in liver.

Metabolic adaptation of pigs to a Mycoplasma hyopneumoniae and Lawsonia intracellularis dual challenge

Respiratory and enteric pathogens such as Mycoplasma hyopneumoniae (Mh) and Lawsonia intracellularis (LI) reduce lean accretion and feed efficiency (FE) in growing pigs. However, the metabolic mechanism by which this occurs is still unknown. Therefore, the primary aim of this study was to examine the metabolic adaptation of pigs presented with a dual Mh and LI challenge (MhLI). A secondary objective was to examine if selection for high FE, modeled by selection for low residual feed intake (RFI), alters molecular response to disease. Using a 2 × 2 factorial design, 6 littermate pairs from a high RFI (HRFI) and 6 littermate pairs from a low RFI (LRFI) line (barrows, 66 ± 2 kg BW) were selected, with 1 pig from each pair assigned to individual pens in either the challenge or the nonchallenge (control) rooms (n = 6 barrows per line/challenge). On days post inoculation (dpi) 0, MhLI pigs were inoculated intragastrically with LI and intratracheally with Mh. Pig and feeder weights were recorded at dpi 0, 7, 14, and 21. On dpi 21, pigs were euthanized and tissues and blood were collected. Markers of oxidative stress, skeletal muscle metabolism and proteolysis, and liver gluconeogenesis were evaluated to determine the effects of MhLI, RFI line, and their interaction. The interaction of line and challenge was not significant (P > 0.05) for any measure. Overall, MhLI pigs had lower ADG (38%, P < 0.001), ADFI (25%, P < 0.001), and G:F (19%, P = 0.012) compared with controls. As expected, LRFI pigs had lower ADFI (P = 0.028) for the same ADG, giving them greater G:F (P = 0.021) than HRFI pigs. Challenged pigs had greater reactive oxygen species (ROS) production in the LM and liver (P < 0.10) but did not have greater skeletal muscle proteolysis. Liver gluconeogenesis was also not upregulated (P > 0.05) due to MhLI. These results provide further evidence that selection for LRFI does not negatively affect response to disease. In addition, these results suggest that postabsorptive metabolic functions are altered due to MhLI challenge. The MhLI challenge induced mitochondrial dysfunction, evident by greater ROS production, and caused pigs to favor glycolytic energy generation. However, skeletal muscle proteolysis and liver gluconeogenesis were not upregulated during MhLI challenge. These data suggest that during mild disease stress, pigs can meet energy demands without reliance on nutrient mobilization and gluconeogenesis.

Porcine epidemic diarrhea virus reduces feed efficiency in nursery pigs

Porcine epidemic diarrhea virus (PEDV) infects enterocytes and in nursery pigs, results in diarrhea, anorexia, and reduced performance. Therefore, the objective of this study was to determine how PEDV infection influenced growth performance and repartitioning of amino acids and energy in nursery pigs. A total of 32 barrows and gilts, approximately 1 wk post-wean (BW = 8.46 ± 0.50 kg), and naïve for PEDV were obtained, weighed, and allotted based on sex and BW to one of two treatments: 1) Control, PEDV naïve and 2) PEDV-inoculated (PEDV) with eight pens of two pigs each per treatment. On day post-inoculation (dpi) 0, PEDV pigs were inoculated via intragastric gavage with PEDV isolate (USA/Iowa/18984/2013). Pig and feeder weights were recorded at dpi −7, 0, 5, and 20 in order to calculate ADG, ADFI, and G:F. Eight pigs per treatment were euthanized on dpi 5 and 20, and tissues and blood were collected. At dpi 5, all PEDV pigs were PCR positive for PEDV in feces. Overall, PEDV pigs tended (P < 0.10) to increase ADFI, which resulted in reduced (P < 0.05) feed efficiency. At dpi 5, PEDV pigs had reduced (P < 0.05) villus height and increased (P < 0.05) stem cell proliferation in the jejunum compared with Control pigs. Pigs inoculated with PEDV had increased (P < 0.05) serum haptoglobin and increased insulin-to-glucose ratios compared with Control pigs at dpi 5. Markers of muscle proteolysis were not different (P > 0.05) between treatments within dpi; however, at dpi 5, 20S proteasome activity was increased (P < 0.05) in longissimus dorsi of PEDV pigs compared with Control pigs. Liver and jejunum gluconeogenic enzyme activities were not different (P > 0.05) between treatments within dpi. Overall, PEDV-inoculated pigs did recover the absorptive capacity that was reduced during PEDV infection by increasing proliferation of intestinal stem cells. However, the energy and nutrients needed to recover the epithelium may be originating from available luminal nutrients instead of muscle proteolysis and gluconeogenesis. This study provides insight into the effects of an enteric coronavirus on postabsorptive metabolism in nursery pigs.

Impact of PRRSV infection and dietary soybean meal on ileal amino acid digestibility and endogenous amino acid losses in growing pigs

Porcine reproductive and respiratory syndrome virus (PRRSV) is a significant disease in the swine industry, and increasing soybean meal (SBM) consumption during this disease challenge may improve performance. Our objectives were to determine the impact of SBM level on apparent total tract (ATTD) and ileal (AID) digestibility during PRRSV infection and to determine ileal basal endogenous losses (BEL) during PRRSV infection. Forty PRRSV negative gilts were fitted with a T-cannula in the distal ileum. Treatments were arranged in a 2 × 2 factorial with high and low SBM (HSBM, 29% vs. LSBM, 10%), with and without PRRSV (n = 6/treatment). The remaining pigs (n = 8/challenge status) were fed a N-free diet. Chromic oxide was used as an indigestible marker. On day post inoculation (dpi) 0, at 47.7 ± 0.57 kg BW, 20 pigs were inoculated with live PRRSV; 20 control pigs were sham inoculated. Infection was confirmed by serum PCR. Feces were collected at dpi 5 to 6 and dpi 16 to 17, and ileal digesta collected at dpi 7 to 8 and dpi 18 to 19. Feed, feces, and digesta were analyzed for DM, N, and GE. Digesta and feed were analyzed for AA. Data were analyzed in a 2 × 2 + 2 factorial design to determine main effects of diet and PRRSV and their interaction. Data from N-free fed pigs were analyzed separately to determine BEL and hindgut disappearance due to PRRSV infection. All control pigs remained PRRSV negative. There were no interactions for AID of AA; however, HSBM reduced DM, GE, Lys, and Met AID and increased Arg and Gly AID during both collection periods (P < 0.05). At dpi 7 to 8 only, PRRSV reduced DM and GE AID (P < 0.05). At 7 to 8 dpi, BEL of Arg, Ala, and Pro were reduced (P < 0.05) due to PRRSV by 64%, 39%, and 94%, respectively. At dpi 18 to 19, BEL of Thr tended (P = 0.06) to be increased in PRRSV-infected pigs; however, no other differences were observed. Pigs fed LSBM had increased Lys, Met, Thr, Trp, and Pro standardized ileal digestibility (SID), primarily at 7 to 8 dpi. At 7 to 8 dpi, PRRSV reduced Arg, Gly, and Pro SID (P < 0.01), and SID Pro continued to be reduced by 17% at dpi 18 to 19. Compared with HSBM pigs, LSBM reduced hindgut disappearance of DM and GE at dpi 5 to 8 and dpi 16 to 19, while N disappearance was reduced at dpi 5 to 8. There were no differences between control and PRRSV N-free fed pigs. Altogether, SBM inclusion impacts SID of AA and hindgut disappearance of nutrients, regardless of PRRSV. In contrast, there is minimal impact of PRRSV on BEL, and therefore, SID of most AA are not different.

Acute heat stress activated inflammatory signaling in porcine oxidative skeletal muscle

Despite well-studied clinical manifestations, intracellular mechanisms of prolonged hyperthermic injury remain unclear, especially in skeletal muscle. Given muscle's large potential to impact systemic inflammation and metabolism, the response of muscle cells to heat-mediated injury warrants further investigation. We have previously reported increased activation of NF-κB signaling and increased NF-κB and AP-1-driven transcripts in oxidative skeletal muscle following 12 h of heat stress. The purpose of this investigation was to examine early heat stress-induced inflammatory signaling in skeletal muscle. We hypothesized that heat stress would increase NF-κB and AP-1 signaling in oxidative skeletal muscle. To address this hypothesis, 32 gilts were randomly assigned to one of four treatment groups (n = 8/group): control (0 h: 21°C) or exposed to heat stress conditions (37°C) for 2 h (n = 8), 4 h (n = 8), or 6 h (n = 8). Immediately following environmental exposure pigs were euthanized and the red portion of the semitendinosus muscle (STR) was harvested. We found evidence of NF-κB pathway activation as indicated by increased protein abundance of NF-κB activator IKK-α following 4 h and increased total NF-κB protein abundance following 6 h of heat stress. Heat stress also stimulated AP-1 signaling as AP-1 protein abundance was increased in nuclear fractions following 4 h of heat stress. Interleukin-6 protein abundance and activation of the JAK/STAT pathway were decreased in heat stressed muscle. These data indicate that heat stress activated inflammatory signaling in the porcine STR muscle via the AP-1 pathway and early activation of the NF-κB pathway.

Effect of lower-energy, higher-fiber diets on pigs divergently selected for residual feed intake when fed higher-energy, lower-fiber diets

Residual feed intake (RFI) is the difference between observed and predicted feed intake of an animal, based on growth and maintenance requirements. In Yorkshire pigs, divergent selection for increased (Low RFI) and decreased (High RFI) RFI was carried out over 10 generations (G) while feeding a corn- and soybean-meal-based, higher-energy, lower-fiber (HELF) diet. In G8 to G10, representing 4 replicates, barrows and gilts (n = 649) of the RFI lines were fed the HELF diet and a diet incorporating coproducts that were lower in energy and higher in dietary fiber (LEHF). The diets differed in ME, 3.32 vs. 2.87 Mcal/kg, and in neutral detergent fiber (NDF), 9.4% vs. 25.9%, respectively. The impact of the LEHF diet on 1) performance and growth, 2) diet digestibility, 3) genetic parameter estimates, and 4) responses to selection for RFI, when fed the HELF, was assessed. In general, the LEHF diet reduced the performance of both lines. When fed the HELF diet, the Low RFI pigs had lower (P < 0.05) ADFI (-12%), energy intake (-12%), ADG (-6%), and backfat depth (-12%); similar (P > 0.05) loin muscle area (LMA; +5%); and greater (P < 0.05) feed efficiency (i.e., 8% higher G:F and 7% lower RFI) than the High RFI line. These patterns of line differences were still present under the LEHF diet but differences for ADFI (-11%), energy intake (-10%), G:F (+2%), and RFI (-6%) were reduced compared to the HELF diet. Apparent total tract digestibility (ATTD) of the HELF and LEHF diets was assessed using 116 barrows and gilts from G8. When fed the HELF diet, ATTD of DM, GE, N, and NDF were similar between lines (P ≥ 0.27), but when fed the LEHF diet, the Low RFI pigs had greater digestibility (7%, 7%, 10%, and 32%) than the High RFI line (P ≤ 0.04). To measure responses to selection for RFI and estimate genetic parameters, data from all 10 generations were used (HELF; n = 2,310; LEHF, n = 317). Heritability estimates of performance traits ranged from 0.19 to 0.63, and genetic correlations of traits between diets were high and positive, ranging from 0.87 (RFI) to 0.99 (LMA). By G10, RFI in the Low RFI line was 3.86 and 1.50 genetic SD lower than in the High RFI line when fed the HELF and LEHF diets, respectively. Taken together, the results of this study demonstrate that responses to selection for RFI when fed a HELF diet are not fully realized when pigs are fed an extremely LEHF diet. Thus, feeding diets that differ from those used for selection may not maximize genetic potential for feed efficiency.

Effects of heat stress during porcine reproductive and respiratory syndrome virus infection on metabolic responses in growing pigs

Heat stress (HS) and immune challenges negatively impact nutrient allocation and metabolism in swine, especially due to elevated heat load. In order to assess the effects of HS during Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) infection on metabolism, 9-wk old crossbred barrows were individually housed, fed ad libitum, divided into four treatments: thermo-neutral (TN), thermo-neutral PRRSV infected (TP), HS, and HS PRRSV infected (HP), and subjected to two experimental phases. Phase 1 occurred in TN conditions (22 °C) where half the animals were infected with PRRS virus (n = 12), while the other half (n = 11) remained uninfected. Phase 2 began, after 10 d with half of the uninfected (n = 6) and infected groups (n = 6) transported to heated rooms (35 °C) for 3 d of continuous heat, while the rest remained in TN conditions. Blood samples were collected prior to each phase and at trial completion before sacrifice. PPRS viral load indicated only infected animals were infected. Individual rectal temperature (Tr), respiration rates (RR), and feed intakes (FI) were determined daily. Pigs exposed to either challenge had an increased Tr, (P < 0.0001) whereas RR increased (P < 0.0001) with HS, compared to TN. ADG and BW decreased with challenges compared to TN, with the greatest loss to HP pigs. Markers of muscle degradation such as creatine kinase, creatinine, and urea nitrogen were elevated during challenges. Blood glucose levels tended to decrease in HS pigs. HS tended to decrease white blood cell (WBC) and lymphocytes and increase monocytes and eosinophils during HS. However, neutrophils were significantly increased (P < 0.01) during HP. Metabolic flexibility tended to decrease in PRRS infected pigs as well as HS pigs. Fatty acid oxidation measured by CO2 production decreased in HP pigs. Taken together, these data demonstrate the additive effects of the HP challenge compared to either PRRSV or HS alone.

Influence of feeding thermally peroxidized soybean oil on growth performance, digestibility, and gut integrity in growing pigs

Consumption of highly peroxidized oils has been shown to affect pig performance and oxidative status through the development of compounds which differ according to how oils are thermally processed. The objective of this study was to evaluate the effect of feeding varying degrees of peroxidized soybean oil (SO) on parameters of growth performance; lipid, N, and GE digestibility, gut integrity in growing pigs, and plasma Trp. Fifty-six barrows (25.3 ± 3.3 kg initial BW) were randomly assigned to one of four diets containing either 10% fresh SO (22.5 °C) or thermally processed SO (45 °C for 288 h, 90 °C for 72 h, or 180 °C for 6 h), each with an air infusion of 15 L/min. Peroxide values for the 22.5, 45, 90, and 180 °C processed SO were 2.0, 96, 145, and 4.0 mEq/kg, respectively; 2,4-decadienal values for 22.5, 45, 90, and 180 °C processed SO were 2.11,5.05, 547.62, and 323.57 mg/kg, respectively; and 4-hydroxynonenal concentrations of 0.05, 1.05, 39.46, and 25.71 mg/kg with increasing SO processing temperature. Pigs were individually housed and fed ad libitum for a 49 d period to determine the effects of SO peroxidation status on growth performance, including a metabolism period for assessing GE and N digestibility, and N retention. In vivo urinary lactulose to mannitol ratio was also assessed to evaluate potential changes in small intestinal integrity. Although there were no differences observed in ADFI (P = 0.19), ADG was decreased in pigs fed 90 °C SO diet (P = 0.01), while G:F was increased (P = 0.02) in pigs fed 45 °C SO diet compared to the other SO diets. Pigs fed the 90 °C processed SO had the lowest (P = 0.01) DE as a percentage of GE, whereas ME as a percentage of DE was lowest (P = 0.05) in pigs fed the 180 °C SO and 90 °C SO followed by 45 °C SO and fresh SO. Ether extract (EE) digestibility was lowest (P = 0.01) in pigs fed 90 °C SO followed by pigs fed 180 °C SO, 45 °C SO, and fresh SO. The percent of N retained was greatest (P = 0.01) in pigs fed fresh SO followed by pigs fed 45 °C SO, 180 °C SO, and 90 °C, respectively. There were no differences observed among SO treatments for urinary lactulose to mannitol ratio (P = 0.60). Pigs fed SO processed at 90 °C and 180 °C had lower concentrations (P < 0.01) of serum Trp compared to pigs fed the 22.5 °C and 45 °C SO treatments. The presence of lipid peroxidation products, namely several aldehydes, contained in the 90 °C SO diet reduced ADG, GE and EE digestibility, and N balance, but had no impact on gut permeability.

Impact of Mycoplasma hyopneumoniae and Lawsonia intracellularis on the performance of pigs divergently selected for feed efficiency

Feed efficiency (FE) is a valuable trait, yet how genetic selection for enhanced FE affects other processes such as response to disease is unknown. Disease from endemic respiratory and enteric pathogens such as Mycoplasma hyopneumoniae (Mh) and Lawsonia intracellularis (LI) are common in swine production. Therefore, the aim of this study was to examine if pigs selected for high vs. low FE based on residual feed intake (RFI) respond differently to a dual respiratory and enteric challenge. Pigs selected for low RFI (LRFI, high FE) are considered more FE compared to their high RFI (HRFI, low FE) selected counterparts. Using a 2 × 2 factorial design, 25 littermate pairs from the HRFI and 25 littermate pairs from the LRFI line (barrows, 50 ± 7 kg BW) were selected, with one pig from each pair assigned to individual pens in either the challenge or the nonchallenge (control) rooms (n = 25 barrows/line/challenge). On days post inoculation (dpi) 0, the challenged pigs were inoculated with LI and Mh (MhLI). Feed intake, BW, fecal swabs, and serum samples were collected and recorded weekly for 42 d. On dpi -2 and 47, 14 littermate pairs (n = 7 barrows/line/challenge) were utilized for initial and final body composition scans using dual-energy X-ray absorptiometry to calculate longitudinal whole body tissue accretion rates for lean, protein, fat, and bone mineral content. Serum antibody levels and fecal shedding of LI were used to confirm infection. Control pigs remained negative by all measures during the 6-wk trial and MhLI inoculated pigs were confirmed positive via serological antibody responses by dpi 14 for LI and Mh. There were no interactions between RFI line and challenge status for any overall performance parameter (P > 0.05). The 6-wk MhLI challenge resulted in a 17% reduction in ADG, a 12% reduction in ADFI, and a 7% reduction in G:F vs. Controls (P < 0.05). In addition, compared to the Control pigs, MhLI challenge reduced lean, protein, and lipid accretion rates by 16% (P < 0.05). Genetic selection for high FE resulted in decreased ADFI and increased G:F (P < 0.01), but did not impact ADG or tissue accretion vs. low FE pigs. Collectively, these results demonstrate that a dual enteric and respiratory pathogen challenge reduced ADG, ADFI, G:F, and tissue accretion in growing pigs. Further, there was no evidence that selection for enhanced FE based on RFI index affects response to disease.

Short-term heat stress altered metabolism and insulin signaling in skeletal muscle

Heat-related complications continue to be a major health concern for humans and animals and lead to potentially life-threatening conditions. Heat stress (HS) alters metabolic parameters and may alter glucose metabolism and insulin signaling. Therefore, the purpose of this investigation was to determine the extent to which 12 h of HS-altered energetic metabolism in oxidative skeletal muscle. To address this, crossbred gilts (n = 8/group) were assigned to one of three environmental treatments for 12 h: thermoneutral (TN; 21 °C), HS (37 °C), or pair-fed to HS counterparts but housed in TN conditions (PFTN). Following treatment, animals were euthanized and the semitendinosus red (STR) was recovered. Despite increased relative protein abundance of the insulin receptor, insulin receptor substrate (IRS1) phosphorylation was increased (P = 0.0005) at S307, an inhibitory site, and phosphorylated protein kinase B (AKT) (S473) was decreased (P = 0.03) likely serving to impair insulin signaling following 12 h of HS. Further, HS increased phosphorylated protein kinase C (PKC) ζ/λ (P = 0.02) and phosphorylated PKCδ/θ protein abundance (P = 0.02), which are known to regulate inhibitory serine phosphorylation of IRS1 (S307). Sarcolemmal glucose transporter 4 (Glut4) was decreased (P = 0.04) in the membrane fraction of HS skeletal muscle suggesting diminished glucose uptake capacity. HS-mediated increases (P = 0.04) in mechanistic target of rapamycin (mTOR) were not accompanied by phosphorylation of eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1). HS decreased (P = 0.0006) glycogen synthase (GS) and increased (P = 0.02) phosphorylated GS suggesting impaired glycogen synthesis. In addition, HS altered fatty acid metabolic signaling by increasing (P = 0.02) Acetyl-CoA carboxylase (ACC), decreasing (P = 0.005) phosphorylated ATP-citrate lyase (pATPCL) and fatty acid synthase (P = 0.01) (FAS). These data suggest that 12 h of HS blunted insulin signaling, decreased protein synthesis, and altered glycogen and fatty acid metabolism.

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.

Short-term heat stress results in increased apoptotic signaling and autophagy in oxidative skeletal muscle in Sus scrofa

Prolonged environment-induced hyperthermia causes morbidities and mortality in humans and animals and appears to cause organ-specific injury and dysfunction. We have previously determined autophagic dysfunction and apoptotic signaling in oxidative skeletal muscle following prolonged hyperthermia. The aim of this investigation was to extend our knowledge regarding the early chronology of heat stress-mediated apoptotic and autophagic signaling in oxidative skeletal muscle. We hypothesized that 2, 4, and 6 h of hyperthermia would increase apoptosis and autophagy in oxidative skeletal muscle compared to thermoneutral (TN) conditions. Pigs were assigned to four groups (n = 8/group) and exposed to environmental heat stress (37 °C) for 0, 2, 4, or 6 h. Immediately following environmental exposure animals were euthanized and the red portion of the semitendinosus was collected. Markers of apoptotic signaling were increased following 2 h of heating but returned to baseline thereafter, while caspase 3 activity remained elevated 2-3 fold (p < .05) throughout the hyperthermic period. Heat stress increased (p < .05) markers of autophagic activation, and nucleation as well as autophagosome formation and degradation linearly throughout the heating intervention. In addition, 6 h of hyperthermia increased (p < .05) markers of mitophagy. These data suggest that apoptotic signaling precedes increased autophagy during acute heat stress in oxidative skeletal muscle.

The composition of dietary fat alters the transcriptional profile of pathways associated with lipid metabolism in the liver and adipose tissue in the pig

The objective was to investigate the of effect chemical composition of dietary fat on transcription of genes involved in lipid metabolism in adipose tissue and the liver via transcriptional profiling in growing pigs. A total of 48 Genetiporc 6.0 × Genetiporc F25 (PIC, Inc., Hendersonville, TN) barrows (initial BW of 44.1 ± 1.2 kg) were randomly allotted to 1 of 6 dietary treatments. Each experimental diet included 95% of a corn-soybean meal basal diet and 5% cornstarch (control; CNTR), animal-vegetable blend (AV), coconut oil (COCO), corn oil (COIL), fish oil (FO), or tallow (TAL). Pigs were sacrificed on d 10 (final BW of 51.2 ± 1.7 kg) to collect tissues. Expression normalization across samples was performed by calculating a delta cycle threshold (ΔCt) value using . Delta delta cycle threshold (ΔΔCt) values were expressed relative to the CNTR treatment. In adipose tissue, adding dietary fat, regardless of the source, decreased the mRNA abundance of compared with the CNTR ( = 0.014). Pigs fed a COIL-based diet tended to have greater adipose tissue expression of ( = 0.071) than pigs fed the other dietary fat sources tested. Abundance of mRNA was greater in adipose tissue of barrows a fed COIL-based diet than barrows fed CNTR or FO-based diets ( = 0.047). In the liver, adding dietary fat, regardless of source, increased the mRNA abundance of , , , , , and ( ≤ 0.020) and tended to increase the abundance of ( = 0.071) and ( = 0.086) compared with the CNTR. Pigs fed a TAL-based diet had greater hepatic transcription of than pigs fed CNTR-, COCO-, or FO-based diets ( = 0.013). Hepatic transcription of tended to be greater in pigs fed COCO than in pigs fed other dietary fat sources ( = 0.074). Dietary omega-3 fatty acid content tended to negatively correlate with mRNA abundance of ( = 0.065) in adipose tissue and ( = 0.063) in the liver. Dietary fat SFA content was negatively correlated with in the liver ( ≤ 0.039). Dietary fat MUFA content tended to be positively correlated with , , and mRNA abundance in the liver ( ≤ 0.100). To conclude, the intake of omega-3 fatty acids suppressed the mRNA abundance of genes involved in lipolysis in both adipose tissue and the liver. Dietary SFA are greater inhibitors of lipogenesis in adipose tissue than omega-6 fatty acids. Intake of medium-chain fatty acids alters hepatic lipid metabolism differently than intake of long-chain fatty acids.

Short-term heat stress causes altered intracellular signaling in oxidative skeletal muscle

Heat stress (HS) causes morbidities and mortalities, in part by inducing organ-specific injury and dysfunction. Further, HS markedly reduces farm animal productivity, and this is especially true for lean tissue accretion. The purpose of this investigation was to determine the extent to which short-term HS caused muscle dysfunction in skeletal muscle. We have previously found increased free radical injury in skeletal muscle following 24 h of HS. Thus, we hypothesized that HS would lead to apoptosis, autophagy, and decreased mitochondrial content in skeletal muscle. To test this hypothesis, crossbred gilts were divided into 3 groups ( = 8/group): thermal neutral (TN: 21°C), HS (37°C), and pair-fed thermal neutral (PFTN: feed intake matched with heat-stressed animals). Following 12 h of treatment, animals were euthanized and red (STR) and white (STW) portions of the semitendinosus were recovered. Heat stress did not alter intracellular signaling in STW. In STR, the oxidative stress marker malondialdehyde protein and concentration were increased in HS ( = 0.007) compared to TN and PFTN, which was matched by an inadequate antioxidant response, including an increase in superoxide dismutase (SOD) I ( = 0.03) and II relative protein abundance ( = 0.008) and total SOD activity ( = 0.02) but a reduction ( = 0.006) in catalase activity in HS compared to TN. Further, B-cell lymphoma 2-associated X protein ( = 0.02) and apoptotic protease activating factor 1 ( = 0.01) proteins were increased by HS compared to TN and PFTN. However, caspase 3 activity was similar between groups, indicating a lack of apoptotic execution. Despite increased initiation, autophagy appeared to be inhibited by HS as the microtubule-associated protein A/B light chain 3 II/I ratio and mitofusin-2 proteins were decreased ( < 0.03) and sequestosome 1(p62) protein abundance was increased ( = 0.001) in HS compared to TN and PFTN. Markers of mitochondrial content cytochrome c, cytochrome c oxidase IV, voltage-dependent anion channel, pyruvate dehydrogenase, and prohibitins 1 were increased ( < 0.05) in HS compared to TN, whereas mitochondrial biogenesis and mitophagy markers were similar between groups. These data demonstrate that HS caused aberrant intracellular signaling, which may contribute to HS-mediated muscle dysfunction.

Porcine Reproductive and Respiratory Syndrome virus reduces feed efficiency, digestibility, and lean tissue accretion in grow-finish pigs

Porcine reproductive and respiratory syndrome (PRRS) virus is a major swine virus that causes reproductive impairment in sows, as well as respiratory disease, reduction in growth rates, and mortalities in all ages of pigs. The objective of this study was to quantify the impact PRRS has on grower-finisher pig feed efficiency and tissue accretion rates. Thirty PRRS naïve, littermate pairs of maternal line Choice Genetics gilts (33.6 ± 0.58 kg BW) were selected and pairs split across 2 barns consisting of 5 pens (n = 6 pigs/pen per barn). Pigs in both barns were fed corn-soybean-DDGS diets ad libitum. All pigs in one barn were inoculated (CHAL) via an i.m. injection of a live PRRS strain isolated from the region (0 d post inoculation, dpi), while pigs in the other barn were given a saline control injection (CONT). Pig performance (ADG, ADFI, G:F) was assessed from 35 kg BW until each group reached market BW (128 kg). Additionally, longitudinal apparent total tract digestibility (ATTD) and body composition was assessed using Dual-energy X-ray absorptiometry (DXA) post inoculation (dpi) to estimate lean, protein, fat and bone accretion rates. Serological data from CHAL pigs showed that PRRS titers peaked 7 dpi and these pigs seroconverted by 35 dpi. According to both genomic and protein PRRS titers, CONT pigs were naïve to CHAL throughout the study. The PRRS infection reduced (P < 0.001) ATTD of dry matter, energy and nitrogen by 3 to 5% at 21 dpi and the reduction in ATTD persisted after 65 dpi. Compared to the CONT, CHAL pigs had decreased ADG (0.89 vs. 0.80 kg/d, P < 0.001), ADFI (2.05 vs. 1.93 kg/d, P < 0.001), and G:F (0.44 vs. 0.41 kg/d, P < 0.001) over the entire test period. The CHAL pigs also had attenuated DXA predicted whole body accretion of lean (547 vs. 633 g/d, P = 0.001), protein (109 vs. 126 g/d, P = 0.001) and fat (169 vs. 205 g/d, P = 0.001) compared to their CONT counterparts from dpi 0 to 80. Based on carcass data at slaughter (and consistent with the DXA data), CHAL pigs had leaner carcasses and reduced yields. These data clearly demonstrate that PRRS infection reduces digestibility, feed efficiency and protein accretion rates in grower-finisher pigs.

Effects of Diet and Genetics on Growth Performance of Pigs in Response to Repeated Exposure to Heat Stress

Heat stress (HS) is one of the costliest issues in the U.S. pork industry. Aims of the present study were to determine the consequences of repeated exposure to HS on growth performance, and the effects of a high fiber diet, the genetic potential for high lean tissue accretion, and the genetic potential for residual feed intake (RFI) on resilience to HS. Barrows (n = 97) from three genetic lines (commercial, high RFI, low RFI) where subjected three times to a 4-day HS treatment (HS1, HS2, and HS3) which was preceded by a 9-day neutral (TN) adaptation period (TN1) and alternated by 7-day periods of neutral temperatures (TN2, TN3, and TN4). Body weight gain (BWG), feed intake (FI), feed conversion efficiency (FCE), RFI, and the drop in BWG and FI between TN and HS were estimated for each period, and slaughter traits were measured at the end of TN4. Commercial pigs had lower FI when fed a high fiber diet compared to a regular diet (2.70 ± 0.08 vs. 2.96 ± 0.08 kg/d; P < 0.05), while no differences were found for BWG, RFI or FCE. HS reduced FI, BWG, and FCE, increased RFI, and resulted in leaner pigs that generate smaller carcasses at slaughter. In TN, commercial pigs grew faster than the low and high RFI pigs (1.22 ± 0.06 vs. 0.720 ± 0.05 and 0.657 ± 0.07; P < 0.001) but growth rates were not significantly different between the lines during HS. Growth rates for the low RFI and high RFI pigs were similar both during TN and during HS. Pigs of interest for genetic improvement are those that are able to maintain growth rates during HS. Our results show that response in growth to HS was repeatable over subsequent 4-d HS cycles, which suggests the potential for including this response in the breeding index. The best performing animals during HS are likely those that are not highly superior for growth in TN.

Temporal proteomic response to acute heat stress in the porcine muscle sarcoplasm

Heat stress (HS) is an important topic in the swine industry, costing hundreds of millions of dollars in economic losses annually, figures that could easily rise in light of global climate change. Muscle biology during HS is particularly important given skeletal muscle's large proportion to the body and its ultimate conversion to meat. Here we report the proteomic changes that occur during acute HS (37°C and 40% relative humidity) lasting 2, 4, or 6 h in the muscle sarcoplasm of growing pigs in comparison with 6 h of thermal neutral (TN; 21°C and 70% relative humidity) conditions ( = 8 per treatment). The red and white areas of the semitendinosus muscle were used to compare the differential effects of HS on oxidative or glycolytic muscles. The results support the hypothesis of proteomic profile differences between the acute HS and TN groups. Altered abundance ( < 0.05) of several proteins occurred in as little as 2 h of HS, affecting metabolism, cell structure, and chaperone, antioxidant, and proteolytic activity. We determined that the muscle HS response is both fiber type and time specific. Overall, more differences were observed in the red semitendinosus than in the white semitendinosus, although the time point at which differences were observed varied. These data show that as little as 2 h of HS has measurable effects on muscle proteins, indicating that acute HS has the potential to impair muscle function and growth.

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.

Infection with Porcine Reproductive and Respiratory Syndrome virus (PRRSv) impacts immune cell metabolism without evidence of cell-mediated immune response

Specific metabolic pathways affect immune cell differentiation and function, and the metabolic state of leukocytes may provide a signature associated with a particular condition or treatment. Health challenge in food production animals may warrant dietary changes to meet metabolic demand of the immune system. Porcine reproductive and respiratory syndrome virus (PRRSV) infection negatively impacts pig performance, and the PRRSV-specific immune response is inefficient at providing protection. Given the poor cell-mediated response induced by infection, we hypothesized that the metabolic profile of peripheral blood mononuclear cells (PBMC) from PRRSV-infected pigs would not show a shift to glycolysis, which is a hallmark of T effector cells. Using an Extracellular Flux Analyzer (Seahorse Biosciences) we interrogated the glycolytic and mitochondrial function of PBMC following infection of pigs with PRRSV, and PRRSV-specific cell-mediated immunity. Basal glycolysis of PBMC was not significantly impacted by PRRSV infection, but contrary to our hypothesis, glycolytic capacity and reserve were significantly increased in PBMC from PRRSV-infected pigs over non-infected pigs. The effect of PRRSV infection on PBMC mitochondrial respiration was minimal, with a slight increase in spare respiratory capacity detected. Despite the increased glycolytic capacity of PBMC, there was not a detectable PRRSV-specific cell-mediated immune response. Thus, while there was metabolic signature of lymphocyte activation, it was not associated with a functional response.

Short-term heat stress alters redox balance in porcine skeletal muscle

Heat stress contributes to higher morbidity and mortality in humans and animals and is an agricultural economic challenge because it reduces livestock productivity. Redox balance and associated mitochondrial responses appear to play a central role in heat stress-induced skeletal muscle pathology. We have previously reported increased oxidative stress and mitochondrial content in oxidative muscle following 12 h of heat stress. The purposes of this investigation were to characterize heat stress-induced oxidative stress and changes in mitochondrial content and biogenic signaling in oxidative skeletal muscle. Crossbred gilts were randomly assigned to either thermal neutral (21°C; n = 8, control group) or heat stress (37°C) conditions for 2 h (n = 8), 4 h (n = 8), or 6 h (n = 8). At the end, their respective environmental exposure, the red portion of the semitendinosus muscle (STR) was harvested. Heat stress increased concentration of malondialdehyde (MDA) following 2 and 4 h compared to thermal neutral and 6 h, which was similar to thermal neutral, and decreased linearly with time. Protein carbonyl content was not influenced by environment. Catalase activity was increased following 4 h of heat stress and superoxide dismutase activity was decreased following 6 h of heat stress compared to thermal neutral conditions. Heat stress-mediated changes in antioxidant activity were independent of altered protein abundance or transcript expression. Mitochondrial content and mitochondrial biogenic signaling were similar between groups. These data demonstrate that heat stress caused a transient increase in oxidative stress that was countered by a compensatory change in catalase activity. These findings contribute to our growing understanding of the chronology of heat stress-induced intracellular dysfunctions in skeletal muscle.

The effect of porcine reproductive and respiratory syndrome virus and porcine epidemic diarrhea virus challenge on growing pigs II: Intestinal integrity and function

The objective of this study was to determine if intestinal function and integrity is altered due to porcine reproductive and respiratory syndrome (PRRS) virus and porcine epidemic diarrhea (PED) virus infection in growing pigs. Forty-two gilts (16.8 ± 0.6 kg BW), naïve for PRRS and PED, were selected and randomly assigned to 1 of 4 treatments: 1) a control (CON; = 6), 2) PRRS virus challenge only (PRRS; = 12), 3) PED virus challenge only (; = 12), or 4) coinfection of PRRS + PED viruses (PRP; = 12). Treatments 2 and 4 were inoculated with a live field strain of PRRS virus on d 0 after inoculation. Treatments 3 and 4 were inoculated with PED virus on 14 d after inoculation (dpi) and all pigs were euthanized 7 d later (21 dpi). Infection with PRRS virus was determined by viremia and seroconversion. Fecal quantitative PCR was used to confirm PED virus infection. Control pigs remained PRRS and PED virus negative throughout the study. Compared with the CON, intestinal morphology was unaffected by PRRS. As expected, PED and PRP treatments resulted in duodenum, jejunum, and ileum villus atrophy compared with the CON treatment ( < 0.01). Ex vivo transepithelial electrical resistance (TER) did not differ between CON and PRRS pigs (P < 0.05) but was reduced by 40% in PED alone ( < 0.01). Interestingly, TER was increased ( < 0.01) in the PRP pigs. Active transport of glucose was increased in PRRS pigs over CON pigs ( < 0.01), whereas PED had pigs increased ( < 0.01) active glutamine transport over the CON pigs. Jejunum GLUT2 mRNA abundance and sucrase, maltase, and Na+/K+ adenosine triphosphatase activities tended to be increased in PRRS pigs compared with CON pigs ( < 0.06). The jejunum AA transporter, SLC6A14, and mucin 2 mRNA abundance tended to be increased in PED-only pigs ( < 0.10). These data suggest that PRRS infection supports a higher affinity for glucose uptake, whereas PED favors glutamine uptake. Interestingly, digestive machinery during PED challenge remained intact. Altogether, PED but not PRRS challenges alter intestinal morphology and integrity in growing pigs.