Studies were conducted to investigate the interactive effects of exogenous enzymes andorganic acids on in vitro and in vivo nutrient digestion and growth performance of broiler chicks.In Study 1, five exogenous enzyme products including ??-glucanase, xylanase, amylase, ??-galactosidase and protease, were assayed in triplicate at their optimum pH levels and at pH levelsof 3.0, 6.0, 6.5, 7.0 and 7.5, which were used to simulate pH levels found in the gizzard, the diet,the crop, and the proximal and distal parts of small intestine, respectively. The pH gradient wasobtained by dissolving the enzymes in different buffers. Results suggested that the pH levelscommonly found in the avian digestive tract were either too high or too low for maximumactivity of the exogenous enzymes, such as ??-galactosidase and protease.In Study 2, broiler chicks were fed corn basal, barley basal or wheat basal diets withdifferent levels or different sources of organic acids. Dietary inclusion of graded levels oforganic acids linearly reduced the pH of the diet and crop content, but not the pH of the digestasampled in the gizzard and small intestine. The inclusion of 2% organic acids (citric acid orfumaric acid) in broiler diets had either no effect or negative effects on chick growthperformance.In Study 3, an in vitro model was used to simulate the chicken's digestive process in thecrop, the gizzard and the small intestine. Soybean meal and raw whole soybeanwere used as substrates. Graded levels of either ??-galactosidase (0 to 13,792 units/kg) or protease(0 to 888 units/kg) and 0 or 2% citric acid were added to the substrates in a factorialarrangement. Reducing sugars, ??-amino nitrogen and trypsin inhibitor content were measured.The data indicated that increasing levels of ??-galactosidase linearly increased the release of thereducing sugars from the soybean meal. Addition of citric acid further increased the activity of ??-galactosidase, resulting in more reducing sugars were released. Increasing the supplementarylevels of protease linearly increased the ??-amino nitrogen release from the soybean meal and rawwhole soybean. Trypsin inhibitor content in the raw whole soybean was not influenced by theapplication of the protease.In Study 4, broilers were fed low energy or normal energy basal diets with ??-galactosidase,amylase and acidification of diet and water. Growth performance, AMEn and digestibility ofDM, CP and NDF were observed. Alpha-galactosidase improved the AMEn of the diets andincreased the weight gain and feed intake of broiler chicks. Citric acid decreased the crop pH andenhanced the activity of ??-galactosidase in the crop. Citric acid decreased the AMEn of the dietsand chick growth performance. These effects were corrected by supplementing ??-galactosidase.The activity of ??-galactosidase was enhanced by simultaneously using organic acid. Thenegative effects on chick growth performance by dietary inclusion of organic acids werecorrected by simultaneously using ??-galactosidase.

The focus here is on the log-normal version of the spatial interaction model. In this context, we consider spatial econometric specifications that can be used to accommodate two types of dependence scenarios, one involving endogenous interaction and the other exogenous interaction. These model specifications replace the conventional assumption of independence between origin-destination-flows with formal approaches that allow for two different types of spatial dependence in flow magnitudes. Endogenous interaction reflects situations where there is reaction to feedback regarding flow magnitudes from regions neighboring origin and destination regions. This type of interaction can be modeled using specifications proposed by LeSage and Pace (2008) who use spatial lags of the dependent variable to quantify the magnitude and extent of feedback effects, hence the term endogenous interaction. Exogenous interaction represents a situation where spillover arise from nearby (or perhaps even distant) regions, and these need to be taken into account when modeling observed variation in flows across the network of regions. In contrast to endogenous interaction, these contextual effects do not generate reaction to the spillovers, leading to a model specification that can be interpreted without considering changes in the long-run equilibrium state of the system of flows. We discuss issues pertaining to interpretation of estimates from these two types of model specification, and provide an empirical illustration. (authors' abstract)

In the well known SIR endemic model, the infection-free steady state is globally stable for R0 < 1 and unstable for R0 > 1. Hence, we have a forward bifurcation when R0 = 1. When R0 > 1, an asymptotically stable endemic steady state exists. The basic reproduction number R0 is the main threshold bifurcation parameter used to determine the stability of steady states of SIR endemic models. In this thesis we study extensions of the SIR endemic model for which a backward bifurcation may occur at R0 = 1. We investigate the biologically reasonable conditions for the change of stability. We also analyse the impact of di erent factors that lead to a backward bifurcation both numerically and analytically. A backward bifurcation leads to sub-critical endemic steady states and hysteresis. We also provide a general classi cation of such models, using a small amplitude expansion near the bifurcation. Additionally, we present a procedure for projecting three dimensional models onto two dimensional models by applying some linear algebraic techniques. The four extensions examined are: the SIR model with a susceptible recovered class; nonlinear transmission; exogenous infection; and with a carrier class. Numerous writers have mentioned that a nonlinear transmission function in relation to the infective class, can only lead to a system with an unstable endemic steady state. In spite of this we show that in a nonlinear transmission model, we have a function depending on the infectives and satisfying certain biological conditions, and leading to a sub-critical endemic equilibriums.

In the well known SIR endemic model, the infection-free steady state is globally stable for R0 < 1 and unstable for R0 > 1. Hence, we have a forward bifurcation when R0 = 1. When R0 > 1, an asymptotically stable endemic steady state exists. The basic reproduction number R0 is the main threshold bifurcation parameter used to determine the stability of steady states of SIR endemic models. In this thesis we study extensions of the SIR endemic model for which a backward bifurcation may occur at R0 = 1. We investigate the biologically reasonable conditions for the change of stability. We also analyse the impact of di erent factors that lead to a backward bifurcation both numerically and analytically. A backward bifurcation leads to sub-critical endemic steady states and hysteresis. We also provide a general classi cation of such models, using a small amplitude expansion near the bifurcation. Additionally, we present a procedure for projecting three dimensional models onto two dimensional models by applying some linear algebraic techniques. The four extensions examined are: the SIR model with a susceptible recovered class; nonlinear transmission; exogenous infection; and with a carrier class. Numerous writers have mentioned that a nonlinear transmission function in relation to the infective class, can only lead to a system with an unstable endemic steady state. In spite of this we show that in a nonlinear transmission model, we have a function depending on the infectives and satisfying certain biological conditions, and leading to a sub-critical endemic equilibriums.

The experiments reported in this thesis investigate whether the current understanding of crossmodal spatial attention can be applied to rear space, and how sound parameters can modulate crossmodal spatial cuing effects. It is generally accepted that the presentation of a brief auditory cue can exogenously orient spatial attention to the cued region of space so that reaction times (RTs) to visual targets presented there are faster than those presented elsewhere. Unlike the conventional belief in such crossmodal spatial cuing effects, RTs to visual targets were equally facilitated from the presentation of an auditory cue in the front or in the rear, as long as the stimuli were presented ipsilaterally. Moreover, when an auditory cue and a visual target were presented from one of two lateral positions on each side in front, the spatial co-location of the two stimuli did not always lead to the fastest target RTs. Although contrasting with the traditional view on the importance of cue-target spatial co-location in exogenous crossmodal cuing effects, such findings are consistent with the evidence concerning multisensory integration in the superior colliculus (SC). Further investigation revealed that the presentation of an auditory cue with an exponential intensity change might be able to exogenously orient crossmodal spatial attention narrowly to the cued region of space. Taken together, the findings reported in this thesis suggest that not only the location but also sound parameters (e.g., intensity change) of auditory cues can modulate the crossmodal exogenous orienting of spatial attention.

A busca pelo crescimento econÃmico exacerbado gera consequÃncias que comprometem a qualidade de vida das pessoas no Planeta. Nas Ãltimas dÃcadas, o agronegÃcio tem se destacado como mais um elemento que acentuou os desequilÃbrios nas esferas ambiental e social. Nesse cenÃrio, os latifundiÃrios tradicionais expandiram as suas fronteiras agrÃcolas para regiÃes antes nÃo exploradas nessa dimensÃo: o Cerrado Piauiense, que teve como carro chefe de exploraÃÃo o cultivo da soja em grande escala. Assim, a pesquisa teve como objetivo estudar determinados impactos sociais e econÃmicos da cadeia primaria de produÃÃo da soja em uma amostra representativa de Unidades Produtoras do Distrito Nova Santa Rosa do municÃpio de UruÃuÃ-PI. A metodologia do estudo deu-se atravÃs de pesquisas bibliogrÃficas especializadas na temÃtica, associadas à coleta de dados e informaÃÃes de natureza primÃria obtidos junto a 55 Unidades representativas Produtoras de Soja do Distrito Nova Santa Rosa, em UruÃuÃ-PI. Essas foram divididas em dois estratos de dimensÃo. Os dados coletados foram submetidos inicialmente à anÃlise estatÃstica descritiva, por meio do cÃlculo de medidas de valor central e de dispersÃo para as variÃveis quantitativas e foi identificado o espectro dominante das variÃveis qualitativas separadamente para cada substrato de dimensÃo. Em seguida, realizou-se a AnÃlise de Componentes Principais para conhecer a importÃncia de cada variÃvel estudada sobre a variÃncia total disponÃvel atravÃs da definiÃÃo dos fatores. Verificou-se que hà uma grande heterogeneidade entre as Unidades Produtoras, a qual concentrou 78,71% da variaÃÃo total, com destaque para a SuperfÃcie AgrÃria Ãtil, e a proporÃÃo de cereais cultivados, acarretando em uma variaÃÃo dos gastos variÃveis. Genericamente, pode-se constatar que hà uma variedade de diferenciaÃÃo entre os LatifundiÃrios e MesofundiÃrios, centrando-se, sobretudo, nas vantagens com as quais aqueles operam, relativamente a estes. A pesquisa caracterizou-se por indicativos de crescimento econÃmico exÃgeno. Identificou-se a atuaÃÃo de uma empresa multinacional, que monopoliza a comercializaÃÃo de grÃos no Distrito. / The search for the exacerbated economic growth generates consequences that compromise the quality of life on the planet. In recent decades, agribusiness has emerged as one more element which accentuated the imbalances in the environmental and social spheres. In this scenario, traditional landowners expanded their agricultural frontiers to areas not previously explored in this dimension: Piauiense Cerrado, which had the flagship exploration soy cultivation on a large scale. Thus, the research aimed to study certain social and economic impacts of the primary chain of soybean production in a representative sample service units in New District of the city of Santa Rosa UruÃuÃ-IP. The study methodology was given through specialized bibliographic research on the issue, associated with data collection and primary nature of information obtained from 55 Units District Soybean Producers New Santa Rosa, in UruÃuÃ-IP. The study methodology was given through specialized bibliographic research on the issue, associated with data collection and primary nature of information obtained from representative 55 Units District Soybean Producers New Santa Rosa, in UruÃuÃ-PI. These dimensions were divided into two strata. The data collected were subjected to descriptive statistics, through the central measures of value calculation and dispersion for quantitative variables was identified and the dominant spectrum of qualitative variables separately for each dimension of the substrate. Then took place the Principal Component Analysis to know the importance of each variable studied on the total variance available by defining factors. It was found that there is great heterogeneity among the service units, which concentrated 78,71% of the total variation, especially for Land Surface Net, and the proportion of cultivated cereals, resulting in a variation of the variable expenses. Generally, it can be seen that there are a variety of differentiation between Lend Lords and Meium owners, focusing mainly on the advantages with which those operating in respect of these. The research was characterized by indicative of exogenous economic growth. Identified the role of a multinational company that monopolizes the marketing of grain in the District.

Three investigations were conducted to assess the effects of selected bio-active feed additives on tilapia (Oreochromis niloticus) growth performance, feed utilisation, haemato-immunological status, intestinal morphology and microbiology. The first experiment was conducted to evaluate the effects of feeding tilapia semi-practical diets supplemented with exogenous enzymes (phytase, protease or carbohydrase). After six weeks of the dietary supplementation, tilapia fed diets supplemented with exogenous enzymes (phytase and carbohydrase) showed enhanced growth performance and higher microvilli density when compared to the control group. Additionally, the intestinal bacterial community profile of tilapia fed the carbohydrase supplemented diet was significantly altered in contrast to those fed the control diet. In the second experiment, tilapia were fed with practical diets supplemented with exogenous enzymes (phytase, protease or xylanase) for eight weeks. Tilapia fed the xylanase supplemented diet demonstrated significantly higher final body weight (FBW), improved feed conversion ratio (FCR) and better protein efficiency ratio (PER) when compared to the control group. Apparent digestibility coefficients of protein, ash, energy, phosphorus, calcium and sodium were highest in tilapia fed a diet supplemented with phytase. The third experiment was carried out to assess the combined effects of dietary exogenous enzymes (phytase, protease and xylanase) and probiotics (Bacillus subtilis, B. licheniformis and B. pumilus) on tilapia growth performance and health. After seven weeks of feeding, tilapia fed the diet supplemented with both exogenous enzymes and probiotics showed significantly higher FBW, specific growth rate, improved FCR and better PER. The serum lysozyme activity was observed to be significantly higher in tilapia fed the probiotic supplemented diet when compared to the control group. The dietary supplementation with combined exogenous enzymes and probiotics increased intestinal perimeter ratio, microvilli count (density), diameter and subsequently resulted in higher enterocyte absorptive area in tilapia. This study demonstrates that feeding tilapia with dietary exogenous enzymes can enhance growth performance and modulate microbial community profile. In addition, supplementation with both exogenous enzymes and probiotics is capable of improving tilapia growth performance, immune parameters and intestinal morphology.

Chronic wounds represent an under-acknowledged socioeconomic epidemic, affecting 1.8 million new patients per year and costing the US health care system upwards of $25 billion annually. This substantial cost is rapidly growing due to a disproportionate occurrence in the ever-aging population. Key features associated with age-related impairment of wound healing include limited energy and nutrient exchange, unremitting inflammations, increased reactive oxygen species (ROS), and diminished blood flow. Most chronic wound therapies target specific molecular mechanisms; however, there are often multiple mitigating factors that prevent normal wound closure. This is likely one reason most wound therapies are minimally effective. In the standard American diet, carbohydrates are broken down for fuel (glucose). While fasting, starvation, and calorie or carbohydrate restriction, beta-oxidation of stored fats in the liver produces ketone bodies (primarily acetoacetate (AcAc) and β-hydroxybutyrate (βHB) to serve as energy metabolites for extra-hepatic tissues. In addition to enhancing metabolic physiology, ketone bodies have recently been discovered to have signaling properties that are independent of their function as energy metabolites. Here we present the evidence for a novel method of inducing therapeutic ketosis via exogenous ketone supplementation to promote enhanced ischemic wound healing in young and aged Fischer 344 rats. Preliminary mechanistic studies demonstrated that exogenous ketone supplementation enhanced wound healing via increasing proliferation and migration, decreasing lactate production, and decreasing ROS production as well as affecting inflammatory cytokines and growth factors. We conclude that exogenous ketone supplementation will be an effective, cost efficient, low toxicity therapy to promote enhancement of wound healing in an aged population.

This study was conducted with the aim to investigate the efficacy of exogenous enzyme supplementation in releasing metabolisable energy in broiler feeds. Two performance trials were conducted during this study. Effects were measured in terms of the body weight gain, feed intake, feed conversion ratio, mortality and production efficiency factor in broilers. Correct interpretation and practical application of the positive effects of exogenous enzyme supplementation to commercial broiler feeds can aid nutritionists to develop nutritionally balanced broiler feeds at lower costs. The negative effects of anti-nutritional factors in broilers feeds can be greatly reduced with the strategic use of exogenous enzyme addition to the feed. In the first performance trial, four treatment feeds were fed to broilers. The Positive control feed was a balanced diet, formulated according to standard nutrient specifications used by Daybreak Farms, with only the metabolisable energy marginally lower than the standard to ensure that energy was the first limiting nutrient. Nutrient specification met or exceeded recommendations by the NRC (1994). A Negative control feed, similar to the Positive control, was formulated with 0.35 MJ ME / kg feed less than the Positive control. An Avizyme treatment and a Hemicell treatment were formulated similar to the Negative control, with the addition of 0.05% Avizyme and 0.0125% Hemicell to the respective treatments. The addition of Avizyme and Hemicell to the respective treatments was hypothesised to release an additional 0.35 MJ ME / kg feed. Four thousand three hundred and twenty day-old Ross 788 chicks were randomly divided into four treatment groups, each with eight replicates and 135 birds per replicate for the first seven days. After seven days birds were reduced to 126 birds per replicate. In the second performance trial, five treatment feeds were fed to broilers. The Positive control feed was a balanced diet, formulated according to standard nutrient specifications used by Daybreak Farms, with only the metabolisable energy marginally lower than the standard to ensure that energy was the first limiting nutrient. Nutrient specification met or exceeded recommendations by the NRC (1994). Results of the first performance trial indicated that more than the hypothesised 0.35 MJ ME / kg feed was being released from the feed with exogenous enzyme addition. Subsequently, the difference in metabolisable energy between the Negative control and Positive control treatments were increased for the second trial. A Negative control feed, similar to the Positive control, was formulated with 0.45 MJ ME / kg feed less than the Positive control. An Avizyme treatment and a Hemicell treatment were formulated similar to the Negative control, with the addition of 0.05% Avizyme and 0.0125% Hemicell to the respective treatments. A Combination treatment was formulated similar to the Negative control, with the addition of both 0.05% Avizyme and 0.0125% Hemicell to the feed. Seven thousand five hundred and sixty day-old Ross 788 chicks were randomly divided into five treatment groups, each with 12 replicates and 126 birds per replicate. For both trials, birds were housed in environmentally controlled houses with a similar lighting schedule and ad libitum access to feed and water. Body weights, feed intake and mortality were recorded weekly for the duration of the five week performance trials. The data was statistically analysed, using the general linear model function in SAS (Statistical Analysis Systems, 1989; Statistical Analysis Systems, 1994). Fischer’s protected test was used for the post hoc multiple comparison test. Repeated tests were included in the model. The confidence interval was set at 95%. Initial body weight was tested as a covariate in all the analyses. Incorrect dosing of the trial feeds during the first performance trial prevented the evaluation of the treatments for the entire 35 day period. The difference between the Positive control and the Negative control treatments were not large enough to enable the exact determination of the amount of metabolisable energy that the Avizyme released in the feed. It could, however, be concluded that Avizyme addition to a broiler feed increased broiler production efficacy. The Avizyme treatment was contributed at least 0.35 MJ ME / kg feed during the trial released more than 0.35 MJ ME / kg feed during the extended starter phase of the trial. The above mentioned conclusions served as a motivation to increase the metabolisable energy difference between the Positive control and the Negative control treatments for the next performance trial. Addition of Hemicell to the feed contributed 0.35 MJ ME / kg feed over a five week growing period. With the second performance trial, the Avizyme and Hemicell treatments released an additional 0.45 MJ ME / kg feed, supported by broiler production variables similar to the Positive treatment. The Combination treatment was shown to release more than 0.45 MJ ME / kg feed and significantly increased broiler performance. It was concluded that the combination of Hemicell and Avizyme in a broiler ration had a positive synergistic effect on each other in the young broiler, indicating that exogenous enzymes could be more effective in younger broilers. Although exogenous enzymes resulted in the release of a significant amount of additional metabolisable energy in the feed, the addition of these enzymes should undergo economical evaluation to ensure that the addition of these enzymes is viable under commercial circumstances. Addition of Avizyme with a calculated energy contribution of 0.35 MJ ME / kg and 0.45 MJ ME / kg to the feed realised an income over feed cost (IOFC) of 25 c / kg live weight and 4 c / kg live weight, respectively, during the five week period. The Hemicell treatment showed a negative IOFC (suggesting that Hemicell inclusion will decrease profit) of 24 c / kg live weight during the first four weeks of the first production trial and an IOFC of 2 c / kg live weight during the five week period of the second trial. The combination of both enzymes in the feed returned an IOFC of 16 c / kg live weight. In general the income over feed cost was the highest during the starter phase because of a higher efficacy of exogenous enzyme addition in younger broilers. / Dissertation (MSc(Agric))--University of Pretoria, 2012. / Animal and Wildlife Sciences / unrestricted

A series of experiments were conducted to investigate the effects of adding an exogenous proteolytic enzyme (EPE) on the growth performance of beef steers fed growing and finishing diets containing 30% dried distillers grains with solubles (DDGS; Exp. 1), and results corroborated by in vitro ruminal fermentation in continuous cultures (Exp. 2). In Exp. 1, 48 group-penned Angus crossbred steers were randomly assigned to 2 treatments (n = 6) in a completely randomized design: DDGS TMR (DT) without and with EPE (27 mg of azocasein hydrolyzed/min/kg DM TMR). The addition of EPE during the growing phase increased DMI (P = 0.02), but had no effects on final BW, BW change, ADG, and G:F. Adding EPE during the growing phase decreased NDF digestibility, whereas the digestibility of DM, CP, and ADF were not affected. There was a tendency for both ADG (P = 0.09) and final BW (P = 0.11) to increase during the finishing phase without affecting BW change and G:F. As opposed to the growing phase, EPE increased digestibility (P < 0.04) of DM, CP, NDF, and ADF. In Exp. 2, 4 dietary treatments were assessed in continuous cultures; non-DDGS TMR (NDT) or DT finishing beef steer diet was combined without or with EPE in a 2 × 2 factorial design. The DT was the same diet used as the finishing diet in Exp. 1, and dose rate of EPE was the same as Exp. 1. Feeding the DT increased total VFA concentration (P = 0.01) which corresponded with a decreased (P < 0.01) pH compared with the NDT diet (5.8 vs. 6.0) regardless of EPE supplementation. Supplementing EPE tended to increase (P = 0.07) the total VFA concentration in both diets, but only increased digestibility of DM, OM, and NDF when added to the DT diet (P < 0.05), leading to tendencies on TMR × enzyme interaction (P < 0.10). Addition of the EPE product assessed in this study resulted in positive responses in Exp. 1 and 2 when added to finishing beef steer diets, and thus it is clear that use of protease enzyme products may be more effective in high concentrate diets such as finishing beef steer diets containing DDGS.