Effect of increasing the dietary tryptophan to lysine ratio on plasma levels of tryptophan, kynurenine and urea and on production traits in weaner pigs experimentally infected with an enterotoxigenic strain of Escherichia coli.

This experiment examined if immune system stimulation of weaner pigs, initiated by inoculation an enterotoxigenic strain of Escherichia coli (ETEC), increased the requirement for dietary tryptophan (Trp), modulated the inflammatory response, altered plasma levels of Trp and its metabolite kynurenine (Kyn) and effected post-weaning diarrhoea. Individually housed pigs (n = 72) weaned at 21 d of age were allocated to one of six treatments (n = 12) according to a two by three factorial arrangement of (1) with or without ETEC infection and (2) three dietary ratios of standardised ileal digestible (SID) Trp to lysine (Lys) (SID Trp:Lys) of 0.16, 0.20 or 0.24, in a completely randomised block design. Pigs had ad libitum access to diets (per kg 14.13 MJ ME, 12.4 g SID Lys, 195 g crude protein) for 3 weeks after weaning. Pigs were infected with ETEC (O149:K98:K88) at 72, 96 and 120 h after weaning and then bled on day 3, 11 and 19. An increased dietary Trp:Lys ratio increased plasma Trp and Kyn (p < 0.001) without effect of infection. On day 3, pigs fed 0.24 SID Trp:Lys had lower levels of plasma urea than at 0.20 Trp:Lys (p = 0.047) and on day 11, plasma urea was lower at 0.20 than at 0.16 SID Trp:Lys (p = 0.007). Infection increased (p = 0.039) the diarrhoea index and deteriorated faecal consistency from day 4-10 (p < 0.05). Treatments did not affect haptoglobin and acid soluble glycoprotein levels or daily gain and feed intake. However, 0.24 SID Trp:Lys improved (p = 0.021) feed efficiency without an effect of infection. In conclusion, in the absence of dietary antibiotic growth promotants, increasing the dietary SID Trp:Lys ratio to 0.24 improved feed conversion ratio after weaning and increased plasma levels of Trp and Kyn regardless of infection with E. coli.

An epidemiological investigation into the association between biomarkers and growth performance in nursery pigs.

BACKGROUND: Biomarkers are useful tools in research and clinical practice where they are often used to detect and monitor differences in the physiological state of an animal. The proteins IGF-1, IGFBP-3, GHR, CRP, SAA, Hp, IFN-α, IFN-γ, TNF-α, IL-1ß, IL-6, IL-10, and IL-18 have been proposed as potential biomarkers for monitoring growth in livestock. The objective of this study was to determine whether hepatic gene expression of these proposed biomarkers is associated with growth performance in nursery pigs. Herd information and growth parameters were collected for 168 piglets from 8 commercial farms in southern Ontario. From these pigs, a subset of liver tissue samples (n = 74) was used for gene expression analysis of the proposed biomarkers. Multivariable linear regression methods were used to determine whether genetic expression of the proposed biomarkers was associated with growth performance in the nursery. RESULTS: Modelling the herd information and individual piglet traits in relation to growth performance revealed that the weight at weaning and the age at weaning are significantly associated with nursery performance. Average daily gain (ADG) was significantly associated with hepatic IGFBP-3 and GHR expression in the liver (P < 0.05), and tended to be associated with hepatic IGF-1 expression (P = 0.071). Similarly, 9-week body weight was significantly associated with hepatic expression of IGFBP-3 and GHR expression (P < 0.05), and tended to be associated with hepatic expression of IGF-1 (P = 0.055). CONCLUSION: The age and weight at which pigs are weaned is an important determinant for nursery performance. Hepatic gene expression of IGF-1, IGFBP-3, and GHR can be useful biomarkers for monitoring growth performance in nursery pigs.

Immune system stimulation induced by porcine reproductive and respiratory syndrome virus alters plasma free amino acid flux and dietary nitrogen utilization in starter pigs1.

Changes in plasma free amino acid (AA) flux reflect the modification of AA metabolism in different metabolic states. Infectious diseases repartition AA away from protein retention toward processes involved in immune defense, thus impacting AA utilization in pigs. The current study sought to evaluate the effects of disease induced by a live pathogen on plasma free AA flux and whole-body nitrogen (N) utilization. Twenty gilts (BW 9.4 ± 0.9 kg) were surgically catheterized into the jugular vein, individually housed in metabolism crates, and feed-restricted (550 g/d). Intramuscular inoculation of a live field strain of porcine reproductive and respiratory syndrome virus (PRRSV) was used to induce disease. Whole-body N-balance was conducted across 3 d both before PRRSV inoculation (PRRSV-) and also after PRRSV inoculation (PRRSV+). At the end of each N-balance period, a bolus dose of a labeled [U-13C, U-15N]-AA mixture (Ile, Leu, Lys, Met, Phe, Thr, Trp, Val, and Gln) was infused intravenously, followed by serial blood collection for measurement of isotopic enrichment. A double exponential model was fitted with plasma enrichment data for each pig and each AA, and equation parameters were used to estimate plasma free AA flux and pool size. Apparent ileal digestibility (AID) of dietary N was determined using the slaughter technique and an indigestible marker. Blood chemistry, hematology, body temperature, and serum viremia indicated that PRRSV induced effective immune response in pigs (P < 0.05). Challenge with PRRSV reduced the AID of N (P < 0.05), but had no effect on apparent total tract digestibility of dietary energy (P = 0.12). Plasma flux (µmol/kg BW/h) for Met and Thr was increased by PRRSV infection (P < 0.05). A strong tendency of increased Val flux was observed in PRRSV+ pigs (P = 0.06). Infection with PRRSV increased the pool size for Lys, Met, Thr, Trp, Leu, Val, and Gln (P < 0.05). Collectively, these results suggest that PRRSV alters the utilization of dietary N and AA flux, as well as pool size, in growing pigs. The increase in Thr and Met flux in PRRSV+ pigs may be associated with enhanced utilization of these AA for the synthesis of immune system metabolites and increased catabolism of these AA. Thus, dietary Met, Thr, and Val requirements may increase in pigs infected with PRRSV, relative to the requirements for other AA.

Immune system stimulation induced by Escherichia coli lipopolysaccharide alters plasma free amino acid flux and dietary nitrogen utilization in growing pigs.

Changes in plasma free AA flux reflect the modification of AA metabolism in different metabolic states. Immune system stimulation (ISS) in growing pigs may redistribute AA from protein retention towards processes involved in the immune response, thus impacting AA utilization. The aim of the current study was to evaluate the effect of ISS on whole-body nitrogen (N) utilization and the kinetics of plasma free AA. Ten gilts (BW 9.4 ± 1.1 kg) were surgically fitted with jugular vein catheters, individually housed in metabolism crates, and feed-restricted (550 g/d). Repeated intramuscular injections of increasing amounts of Escherichia coli lipopolysaccharide (LPS) were used to induce ISS (30 and 36 µg/kg BW, given 48 h apart). Whole-body N-balance was determined for 3-d before ISS (ISS-) and 3-d during ISS (ISS+). At the end of each N-balance period, a bolus dose of labeled [U-13C, U-15N]-AA mixture (Ile, Leu, Lys, Met, Phe, Thr, Trp, Val, and Gln) was infused intravenously, followed by serial blood collection for determination of isotopic enrichment. A double exponential model was fitted with plasma enrichment data for each pig and each AA, and equation parameters were used to estimate plasma-free AA flux and pool size. Apparent ileal digestibility (AID) of N was determined using the slaughter technique and an indigestible marker. Blood samples were collected before and 76-h after the initiation of ISS and assayed for hematology and blood chemistry. Body temperature (BT) was monitored during the course of study. Blood chemistry, hematology, and BT results indicated that LPS induced effective ISS in pigs (P < 0.05). ISS tended to reduce N retention (P = 0.09) and the N retention-to-N intake ratio (P = 0.08). Apparent total tract digestibility of dietary energy and AID of N were reduced by ISS (P < 0.05). Plasma flux (µmol/kg BW/h) for Ile and Phe was reduced by ISS (P < 0.05). Strong tendencies for decreased Lys flux and N retention were observed in ISS pigs (P < 0.10). ISS increased the pool size for Leu but reduced the pool size for Ile (P < 0.05). Collectively, these results suggest that ISS alters the utilization of dietary N and AA flux, as well as pool size in growing pigs. The decrease in Lys, Phe, and Ile flux during ISS may be attributed to a reduction in whole-body protein synthesis or decreased catabolism of these AA. Relative to other AA, dietary Lys, Phe, and Ile requirements may decrease in ISS pigs.

Growth performance, gastrointestinal and digestibility responses in growing pigs when fed corn-soybean meal-based diets with corn DDGS treated with fiber degrading enzymes with or without liquid fermentation.

Fermenting high fiber ingredients such as distillers dried grains with solubles (DDGS) with feed enzymes may improve their feeding value. We investigated the effects of fermenting corn DDGS with a blend of ß-glucanase and xylanases (XB) on growth performance, gut parameters, and apparent total tract digestibility (ATTD) of nutrients and energy in growing pigs. Dietary treatments were: (1) corn soybean meal-based diet + 30% DDGS (control), (2) control + XB without fermentation (XBNS), and (3) control + DDGS fermented with XB (16% DM) for 3 to 10 d at 40 °C (XBS). Target activities in XB were 1,050 and 5,500 U/g of DDGS for XB, respectively. Diets contained phytase at 750 FTU/kg. Feed samples were taken during fermentation and at feeding for analysis of pH and organic acids. A total of 144 pigs (25 ± 1.0 kg BW) were assigned to pens (three barrows and three gilts) and allocated to the three diets in a two-phase feeding program (3 wk/phase). Diets were fed on ad libitum and were delivered by a computer-controlled liquid feeding system at a feed to water ratio of 1:4, four times per day. Pigs had free access to water. Fecal samples were taken in the final 3 d of phase 2 to determine ATTD using TiO2 marker method and one pig per pen was euthanized for gastrointestinal (GIT) measurements. The pH of diets at feeding time was lower (P < 0.01) for XBS (4.72) compared with control (5.45) and XBNS (5.45). Pigs fed XBNS had higher (P = 0.04) ADG than control in phase 1. In phase 2 and the overall (weeks 0 to 6), ADG and final BW were higher (P = 0.01) for XBNS than XBS but were not different (P > 0.05) from control. There were no diet effects (P > 0.05) on ADFI. Feed to gain (FCR) for XBNS (1.68) and XBS pigs (1.69) was better (P < 0.01) than for control pigs (1.78) in phase 1. There were no diet effects (P > 0.05) on FCR in phase 2 or in the overall. Pigs fed XBNS had lower (P < 0.01) ATTD of CP than control and XBS-fed pigs. Although not different (P > 0.05) from control, pigs fed XBNS had lower (P < 0.05) jejunal crypt depth and ATTD of gross energy than pigs fed XBS. In conclusion, treating corn DDGS with XB with or without liquid fermentation improved feed efficiency in phase 1, suggesting degradation of dietary fibrous components that may limit nutrient utilization in younger pigs. However, these benefits were not observed in phase 2.

The impact of epidermal growth factor supernatant on pig performance and ileal microbiota.

Weaning of pigs can lead to low-feed intake resulting in a lag in growth performance, reduced gut health, and diarrheal diseases. Epidermal growth factor (EGF), the most abundant growth factor in milk, increased weaned pig BW gain and feed efficiency in our previous work. It is believed that intestinal microbiota plays an important role in gut health and pig growth, but limited data are available on the impact of feed additives, such as EGF, on the microbial communities of the intestines. The objective of the study was to investigate if the positive influence of EGF supplementation on weight gain and gut health was related to differences in intestinal microbiota. To examine the efficacy of EGF, a 21-d animal trial was performed using 72 pigs (two equal blocks of 36 pigs with three barrows and three gilts/pen). Pigs were assigned to one of two dietary treatments at weaning (20 ± 2 d of age; n = 6 pens/treatment) balancing across treatment for litter, gender, and initial BW. Recombinant yeast supernatant containing EGF at 120 µg/kg BW/d and without EGF (control) was added to the feed for 21 d, followed by a common diet for 7 d. Pig performance was measured weekly and ileal digesta was collected at day 21 from six pigs/treatment for microbiome analysis. Pigs fed diets containing EGF fermentation supernatant had greater (P = 0.01) daily gain in week 3 and overall resulting in heavier (P = 0.029) BW at day 28, which was consistent to our previous finding. No difference in alpha-diversity (Chao1, Shanon, and Simpson indices) and beta-diversity (weighted and unweighted UniFrac distances) of ileal digesta microbiota between EGF supplemented and control pigs were observed. The relative abundances of bacterial taxa did not differ among treatment groups at the phylum level. The relative abundances of Corynebacterium (0.0 vs. 0.9%), Blautia (0.003 vs. 0.26%), and Coprococcus (0.0 vs. 0.05%) genera, and Rumminococcaceae family (0.001 vs. 0.08%) were decreased (P < 0.05) in EGF group compared to control and were negatively correlated (P < 0.05, r > 0.60) with growth performance. Pathways related to detoxification and carbohydrate metabolism were differentially represented in the luminal bacterial populations. The improved growth of pigs supplemented with EGF supernatant produced by Pichia pastoris may be related to changes in functional capacity of the gut microbial populations. However, the impact on mucosa-associated or large intestinal communities is still unknown.

Evaluation of a porcine model of early aortic valve sclerosis.

BACKGROUND: Calcific aortic valve disease (CAVD) is associated with significant cardiovascular morbidity. While late-stage CAVD is well-described, early pathobiological processes are poorly understood due to the lack of animal models that faithfully replicate early human disease. Here we evaluated a hypercholesterolemic porcine model of early diet-induced aortic valve sclerosis. METHODS: Yorkshire swine were fed either a standard or high-fat/high-cholesterol diet for 2 or 5 months. Right coronary aortic valve leaflets were excised and analyzed (immuno)histochemically. RESULTS: Early human-like proteoglycan-rich onlays formed between the endothelial layer and elastic lamina in the fibrosa layer of valve leaflets, with accelerated formation associated with hypercholesterolemia (P<.05). Lipid deposition was more abundant in hypercholesterolemic swine (P<.001), but was present in a minority (28%) of onlays. No myofibroblasts, MAC387-positive macrophages, or fascin-positive dendritic cells were detected in 2-month onlays, with only scarce myofibroblasts present at 5 months. Cells that expressed osteochondral markers Sox9 and Msx2 were preferentially found in dense proteoglycan-rich onlays (P<.05) and with hypercholesterolemia (P<.05). Features of more advanced human CAVD, including calcification, were not observed in this necessarily short study. CONCLUSIONS: Early aortic valve sclerosis in hypercholesterolemic swine is characterized by the formation of proteoglycan-rich onlays in the fibrosa, which can occur prior to significant lipid accumulation, inflammatory cell infiltration, or myofibroblast activation. These characteristics mimic those of early human aortic valve disease, and thus the porcine model has utility for the study of early valve sclerosis.