Impact of Lawsonia intracellularis and Mycoplasma hyopneumoniae on pig performance and metabolism

Disease from endemic respiratory and enteric pathogen agents such as Mycoplasma hyopneumoniae (Mh) and Lawsonia intracellularis (LI) is common in swine herds worldwide and reduces profits at all production stages. However, the metabolic mechanisms behind these reductions in growth performance and tissue accretion have not been fully explained. Additionally, to minimize feed costs, producers place heavy emphasis on selection for production traits such as enhanced feed efficiency (FE), but genetic selection for higher FE has been touted to have negative consequences on a pig’s ability to respond to disease. Therefore, the overall objective of this thesis was to characterize how a Mycoplasma hyopneumoniae and Lawsonia intracellularis dual challenge (MhLI) alters pig performance and metabolism, using pigs divergently selected for residual feed intake (RFI) as a model for divergence in feed efficiency. Pigs selected for low RFI (LRFI, high feed efficiency) pigs are considered more FE compared to their high RFI (HRFI, low feed efficiency) selected counterparts. To address the overall thesis objective, two research chapters were conducted using grow-finish pigs (Chapter 2 and 3). In Chapter 2, the longitudinal impact of MhLI on growth performance, feed efficiency, and tissue accretion of pigs divergent in RFI was assessed in a 42 day challenge study. We initially hypothesized that MhLI dual challenge would reduce growth performance, protein accretion, and feed efficiency. In Chapter 3, a subset of pigs was randomly selected from the larger cohort used in Chapter 2 for necropsy and tissue collection at 21 days post inoculation (dpi). This subset of pigs was utilized to examine effects of MhLI, RFI line, and their interaction on markers of oxidative stress, skeletal muscle metabolism and proteolysis, and liver gluconeogenesis. We hypothesized that MhLI would alter metabolism to reallocate nutrients toward the immune system, which would be evident by increased skeletal muscle proteolysis and increased liver gluconeogenesis. The challenge model utilized resulted in sub-clinical disease in the lungs and intestinal tract of infected pigs. Overall, the results of this work suggest that genetic selection for enhanced FE (i.e. low RFI) does not alter the ability of pigs to respond to and resolve pathogen challenges due to the hypothesized inability to allocate energy and nutrients to the immune response. This was evident as there were no MhLI x line interactions for any performance (Chapter 2) or post-absorptive metabolism (Chapter 3) parameters assessed. However, this thesis indicates that MhLI dual challenge reduces average daily gain, feed intake, feed efficiency, and lean tissue accretion in growing pigs (Chapter 2). Additionally, MhLI dual challenge alters the post-absorptive skeletal muscle and liver metabolism of grow-finish pigs. The challenged pigs had increased reactive oxygen species (ROS) production in the Longissimus dorsi (LM) and liver, and greater hexokinase to citrate synthase activity ratios, but did not have increased skeletal muscle protein carbonyls or enhanced skeletal muscle proteolysis (Chapter 3). Additionally, gluconeogenesis was not upregulated in the liver due to MhLI dual challenge (Chapter 3). Collectively, this line of investigation demonstrated that a dual respiratory and enteric pathogen challenge in grow-finish pigs resulted in reduced growth performance (17%) and feed efficiency (7%) compared to the non-challenged control pigs, regardless of RFI line. These performance reductions are comparable to the previous body of literature utilizing these two pathogens. The MhLI dual challenge also results in increased mitochondrial ROS production and causes pigs to favor glycolytic energy generation. However, contrary to the initial hypothesis, skeletal muscle proteolysis and liver gluconeogenesis are not upregulated during MhLI challenge. These data suggest that during mild disease stress such as what was observed under this MhLI dual challenge, the pig can meet energy demands without reliance on nutrient mobilization and gluconeogenesis

Quantification of chronic fibrosing interstitial pneumonia on computed tomography

The chronic fibrosing interstitial pneumonias (CFIPs) are diseases which cause progressive and often fatal progressive scarring of the lungs. The recent discovery of the first effective pharmacological therapies for this condition have increased interest in the monitoring of this disease. Due to the complex appearance of the CFIPs on computed tomography, visual quantification of disease severity and extent is limited. The purpose of this thesis was to develop and test a computer algorithm for the automated quantification of pulmonary fibrosis on CT using textural measures known as Minkowski functionals. A computer algorithm was successfully developed and this thesis presents initial results of testing the algorithm on a series of normal scans and on 24 prospectively recruited patients who also underwent a series of other tests including pulmonary function tests and a patient reported symptom questionnaire. The computer output was also compared with the visual assessment of two radiologists. Significant correlations were found between computer calculated lung volume and total lung capacity as measured on pulmonary function tests. We also found a significant correlation between computer calculated fibrosis volume and both gas transfer and forced vital capacity. The radiologists’ visual assessment of fibrosis and the computer estimated fibrosis volume were highly correlated. The novel computer algorithm represents a promising method for quantifying pulmonary fibrosis on CT with potential roles in monitoring disease progression and effects of therapeutic interventions

Active shape model unleashed with multi-scale local appearance

We focus on optimising the Active Shape Model (ASM) with several extensions. The modification is threefold. First, we tackle the over-constraint problem and obtain an optimal shape with minimum energy considering both the shape prior and the salience of local features, based on statistical theory: a compact closed form solution to the optimal shape is deduced. Second, we enhance the ASM searching method by modelling and removing the variations of local appearance presented in the training data. Third, we speed up the convergence of shape fitting by integrating information from multi-scale local features simultaneously. Experiments show significant improvement brought by these modifications, i.e., optimal shape against standard relaxation methods dealing with inadequate training samples; enhanced searching method against standard gradient descent methods in searching accuracy; multi-scale local features against popular coarse-to-fine strategies in convergence speed

Measurement of Antioxidant Activity toward Superoxide in Natural Waters

Antioxidants are a class of molecules that provide a protective function against reactive oxygen species (ROS) in biological systems by out competing physiologically important molecules for ROS oxidation. In natural waters, the reactivity of antioxidants gives an estimate of oxidative stress and may determine the reactivity and distribution of reactive oxidants. We present an analytical method to measure antioxidant activity in natural waters through the competition between ascorbic acid, an antioxidant, and MCLA, a chemiluminescent probe for superoxide. A numerical kinetic model of the analytical method has been developed to optimize analytical performance. Measurements of antioxidant concentrations in pure and seawater are possible with detection limits below 0.1 nM. Surface seawater samples collected at solar noon contained over 0.4 nM of antioxidants and exhibited first-order decay with a half-life of 3-7 minutes, consistent with a reactive species capable of scavenging photochemically produced superoxide

Wavelet appearance pyramids for landmark detection and pathology classification : application to lumbar spinal stenosis

Appearance representation and feature extraction of anatomy or anatomical features is a key step for segmentation and classification tasks. We focus on an advanced appearance model in which an object is decomposed into pyramidal complementary channels, and each channel is represented by a part-based model. We apply it to landmark detection and pathology classification on the problem of lumbar spinal stenosis. The performance is evaluated on 200 routine clinical data with varied pathologies. Experimental results show an improvement on both tasks in comparison with other appearance models. We achieve a robust landmark detection performance with average point to boundary distances lower than 2 pixels, and image-level anatomical classification with accuracies around 85%

Acute infection with Brachyspira hyodysenteriae affects mucin expression, glycosylation, and fecal MUC5AC

IntroductionInfection with strongly β-hemolytic strains of Brachyspira hyodysenteriae leads to swine dysentery (SD), a production-limiting disease that causes mucohemorrhagic diarrhea and typhlocolitis in pigs. This pathogen has strong chemotactic activity toward mucin, and infected pigs often have a disorganized mucus layer and marked de novo expression of MUC5AC, which is not constitutively expressed in the colon. It has been shown that fucose is chemoattractant for B. hyodysenteriae, and a highly fermentable fiber diet can mitigate and delay the onset of SD.MethodsWe used lectins targeting sialic acids in α-2,6 or α-2,3 linkages, N-acetylglucosamine (GlcNAc), α-linked L-fucose, and an immunohistochemical stain targeting N-glycolylneuraminic acid (NeuGc) to investigate the local expression of these mucin glycans in colonic tissues of pigs with acute SD. We used a commercial enzyme-linked immunosorbent assay (ELISA) to quantify fecal MUC5AC in infected pigs and assess its potential as a diagnostic monitoring tool and RNA in situ hybridization to detect IL-17A in the colonic mucosa.ResultsColonic mucin glycosylation during SD has an overall increase in fucose, a spatially different distribution of GlcNAc with more expression within the crypt lumens of the upper colonic mucosa, and decreased expression or a decreased trend of sialic acids in α-2,6 or α-2,3 linkages, and NeuGc compared to the controls. The degree of increased fucosylation was less in the colonic mucosa of pigs with SD and fed the highly fermentable fiber diet. There was a significant increase in MUC5AC in fecal and colonic samples of pigs with SD at the endpoint compared to the controls, but the predictive value for disease progression was limited.DiscussionFucosylation and the impact of dietary fiber may play important roles in the pathogenesis of SD. The lack of predictive value for fecal MUC5AC quantification by ELISA is possibly due to the presence of other non-colonic sources of MUC5AC in the feces. The moderate correlation between IL-17A, neutrophils and MUC5AC confirms its immunoregulatory and mucin stimulatory role. Our study characterizes local alteration of mucin glycosylation in the colonic mucosa of pigs with SD after B. hyodysenteriae infection and may provide insight into host-pathogen interaction

In vivo characterization of connective tissue remodeling using infrared photoacoustic spectra

Premature cervical remodeling is a critical precursor of spontaneous preterm birth, and the remodeling process is characterized by an increase in tissue hydration. Nevertheless, current clinical measurements of cervical remodeling are subjective and detect only late events, such as cervical effacement and dilation. Here, we present a photoacoustic endoscope that can quantify tissue hydration by measuring near-infrared cervical spectra. We quantify the water contents of tissue-mimicking hydrogel phantoms as an analog of cervical connective tissue. Applying this method to pregnant women in vivo, we observed an increase in the water content of the cervix throughout pregnancy. The application of this technique in maternal healthcare may advance our understanding of cervical remodeling and provide a sensitive method for predicting preterm birth

Nutritional approaches to slow late finishing pig growth: implications on carcass composition and pork quality

Although pork producers typically aim to optimize growth rates, occasionally it is necessary to slow growth, such as when harvest facility capacity is limited. In finishing pigs, numerous dietary strategies can be used to slow growth so pigs are at optimal slaughter body weights when harvest facility capacity and/or access is restored. However, the impact of these diets on pork carcass quality is largely unknown. Thus, this study aimed to evaluate the efficacy of dietary strategies to slow growth in late finishing pigs and evaluate their effects on carcass composition and pork quality. Mixed-sex pigs (n = 897; 125 ± 2 kg BW) were randomly allotted across 48 pens and assigned to 1 of 6 dietary treatments (n = 8 pens/treatment): (1) Control diet representative of a typical finisher diet (CON); (2) diet containing 3% calcium chloride (CaCl2); (3) diet containing 97% corn and no soybean meal (Corn); (4) diet deficient in isoleucine (LowIle); (5) diet containing 15% neutral detergent fiber (NDF) from soybean hulls (15% NDF); and (6) diet containing 20% NDF from soybean hulls (20% NDF). Over 42 d, pen body weights and feed disappearance were collected. Pigs were harvested in 3 groups (14, 28, and 42 d on feed) and carcass data collected. From the harvest group, 1 loin was collected from 120 randomly selected carcasses (20 loins/treatment) to evaluate pork quality traits. Overall, ADG was reduced in CaCl2, Corn, and 20% NDF pigs compared with CON pigs (P \u3c 0.001). However, ADFI was only reduced in CaCl2 and 20% NDF pigs compared with CON (P \u3c 0.001). Feed efficiency was reduced in CaCl2 and Corn pigs compared with CON (P \u3c 0.001). Hot carcass weights were reduced in CaCl2 pigs at all harvest dates (P \u3c 0.001) and were reduced in Corn and 20% NDF pigs at days 28 and 42 compared with CON pigs (P \u3c 0.001). In general, CaCl2 and 20% NDF diets resulted in leaner carcasses, whereas the Corn diet increased backfat by 42 d on test (P \u3c 0.05). Loin pH was reduced and star probe increased in CaCl2 pigs compared with CON pigs (P \u3c 0.05); no treatments differed from CON pigs regarding drip loss, cook loss, color, firmness, or marbling (P ≥ 0.117). Overall, these data indicate that several dietary strategies can slow finishing pig growth without evidence of behavioral vices. However, changes to carcass composition and quality were also observed, indicating quality should be taken into consideration when choosing diets to slow growth

Recent Improvements in the SLC Positron System Performance

The positron system is very specific to the SLC in that the positrons are accelerated in the same linac as the electrons that produce them and the electrons with which they collide. Some of the difficulties in tuning this system to peak performance are thus unlikely to be encountered in future linear colliders, but many of the lessons learned in beam matching are useful for future machines. The design and commissioning of this system has been previously reported so we only briefly describe the major subsystems before detailing the tuning and diagnostics involved in optimizing the performance of the overall system

Recent Improvements in the SLC Positron System Performance

The positron system is very specific to the SLC in that the positrons are accelerated in the same linac as the electrons that produce them and the electrons with which they collide. Some of the difficulties in tuning this system to peak performance are thus unlikely to be encountered in future linear colliders, but many of the lessons learned in beam matching are useful for future machines. The design and commissioning of this system has been previously reported so we only briefly describe the major subsystems before detailing the tuning and diagnostics involved in optimizing the performance of the overall system