Optimal nutritional management of growing pigs is constrained by lack of quantitative information on the response of animals between 30 and 110 kg live weight to dietary energy content. Under 'ideal' conditions modern genotypes appear to adjust feed intake to maintain a constant DE intake over a much wider range of dietary energy concentrations than previously thought (Mullan et al, 1998). However, under commercial pen conditions, voluntary feed intake is lower, pigs respond in terms of both growth rate and feed conversion to dietary DE density considerably above the levels currently thought to maximise biological and economic responses. The present study was designed to provide information on the response of growing pigs to dietary energy content under ideal and commercial housing conditions for two growth periods 30-60kg liveweight and 60-100kg liveweight. The results of the pigs kept under individual (ideal) housed conditions were consistent with the literature in that they adjusted their voluntary feed intake with digestible energy density to maintain a constant energy intake. The results of the pigs kept in groups (commercial) housing conditions tended to increase their daily energy intake as the energy density of the feed increased. This increase in energy intake improved the growth rate of the pigs and increased the fat deposition of those pigs. Economic analysis of the experiments involving pigs in groups indicates that formulating diets to a least cost per megajoule of digestible energy is not the most profitable point to set the digestible energy density. Modelling programs need to be used to determine where the least cost per unit of growth of the pig occurs. This is the most economical digestible energy density to formulate too. This will have major impact on the cost of production of piggery operations as the cost of energy is the single most important parameter in the cost of producing a pig.

Optimal nutritional management of growing pigs is constrained by lack of quantitative information on the response of animals between 30 and 110 kg live weight to dietary energy content. Under 'ideal' conditions modern genotypes appear to adjust feed intake to maintain a constant DE intake over a much wider range of dietary energy concentrations than previously thought (Mullan et al, 1998). However, under commercial pen conditions, voluntary feed intake is lower, pigs respond in terms of both growth rate and feed conversion to dietary DE density considerably above the levels currently thought to maximise biological and economic responses. The present study was designed to provide information on the response of growing pigs to dietary energy content under ideal and commercial housing conditions for two growth periods 30-60kg liveweight and 60-100kg liveweight. The results of the pigs kept under individual (ideal) housed conditions were consistent with the literature in that they adjusted their voluntary feed intake with digestible energy density to maintain a constant energy intake. The results of the pigs kept in groups (commercial) housing conditions tended to increase their daily energy intake as the energy density of the feed increased. This increase in energy intake improved the growth rate of the pigs and increased the fat deposition of those pigs. Economic analysis of the experiments involving pigs in groups indicates that formulating diets to a least cost per megajoule of digestible energy is not the most profitable point to set the digestible energy density. Modelling programs need to be used to determine where the least cost per unit of growth of the pig occurs. This is the most economical digestible energy density to formulate too. This will have major impact on the cost of production of piggery operations as the cost of energy is the single most important parameter in the cost of producing a pig.

Chronic subclinical levels of disease occur frequently in intensive swine production and compromise nutrient utilization efficiency. Sulfur amino acids (methionine plus cysteine; M+C) have been implicated in improving the animal’s response to immune system stimulation (ISS). Research objectives were to determine the effects of ISS on the optimal dietary methionine to methionine plus cysteine ratio (M:M+C) and on the fractional synthesis rate (FSR) of albumin, fibrinogen and total protein in plasma, liver, and small intestine (SI) of growing pigs. A nitrogen balance study showed that the optimal M:M+C was increased during ISS and greater than 0.62. In a flooding dose infusion study it was determined that total plasma protein FSR was increased during ISS and tended to decrease with reduced M+C intake. Plasma albumin FSR decreased with reduced M+C intake. The data implicates M+C as important nutrients involved in the immune response and careful dietary supplementation during ISS is necessary. / Funding sponsored by Evonik Degussa, Ontario Pork, the Ontario Ministry of Agriculture, Food and Rural Affairs and the Natural Sciences and Engineering Research Council of Canada.

Two experiments were conducted to determine the effects of phosphorus (P) in growing pigs. In experiment 1, fifty-four pigs were randomly allotted to three diets with available phosphorus (aP) concentrations of 0.23%, 0.17% and 0.11%. In experiment 2, twenty-eight pigs were assigned to four treatments including T1 (diet with 0.23% aP for three wks), T2 (diet with 0.11% aP for wk1 replaced by diet with 0.23% aP for wk2 and wk3), T3 (diet with 0.11% aP for wk1 and wk2 replaced by diet with 0.23% aP for wk3) and T4 (diet with 0.11% aP for all three wks). The 0.11% aP diet proved to be very low with negative effects on performance and bone quality. Reduced dietary P resulted in reduced P intake and reduced P excretion. In conclusion, growing pigs are sensitive to P and environmental pollution because of dietary P can be reduced by dietary manipulation of P.

The objectives of this project were to investigate the effects of dietary lysine restriction on (1) the plasma concentrations of selected metabolites, free AAs, and three growth-related hormones, (2) the gene expression profile in longissimus dorsi muscle growing pigs. Twelve individually penned young barrows (Yorkshire × Landrace; 22.6 ± 2.04 kg) were randomly assigned to two dietary treatments (a lysine-deficient, LDD, and a lysineequate, LAD) diets, respectively. Pigs had ad libitum access to water and their respective diets for 8 weeks, and the ADG, ADFI, and G:F were determined. At the end of the trial, jugular vein blood was collected, and plasma was separated for the analysis of plasma parameters. Also, the longissimus dorsi muscle samples were collected from each pig for gene expression profile analysis. The ADG of LDD pigs was lower than that of LAD pigs, and so was the G:F since there was no difference in the ADFI between the two groups of pigs. The plasma concentrations of lysine, methionine, leucine, and tyrosine were lower, while that of β-alanine was higher, in the LDD pigs. The total plasma protein concentration was lower in the LDD pigs, whereas no differences were observed for the other metabolites, and the plasma concentrations of GF, insulin, and IGF-1 between the two groups. While gene expression profile results showed that sixty-nine genes were found differentially expressed (Benjamin-Hochberg corrected P-value < 0.05) in Diet I vs. Diet II pigs, of which 29 genes were down-regulated (Log₂ fold change (FC) < - 0.58) and 40 genes were up-regulated (Log₂ FC > 0.58). Furthermore, bioinformatic analyses revealed that the upregulation and downregulation of the DEGs may negatively affect the muscle protein turnover, structural development, and lipid metabolism of skeletal muscle. In conclusion, these results indicate that the lack of lysine including other two EAA as protein building block must be the primary reason for the compromised G:F ratio and ADG. The changes in the performance might be associated with some cell signaling and metabolic pathways suggested from the Bioinformatic results; however, may not involve the GH/IGF-1 axis.

The objective of these studies was to determine the optimum standardized ileal digestible tryptophan to lysine (SID Trp:Lys) ratio for growing pigs fed both U.S.–type (corn–soybean meal) and non–U.S.–type (wheat–barley) diets. When feeding U.S.–type diets, average daily gain (ADG) and plasma urea nitrogen (PUN) concentrations improved as SID Trp:Lys ratios increased, yielding optimum ratios of 15.32% (P<0.001) and 15.25% (P<0.001), respectively. Averaging these resulted in an optimum SID Trp:Lys ratio of 15.29%. In non–U.S.–type diets, feeding increasing SID Trp:Lys ratios improved ADG and PUN, displaying optima of 15.99% (P=0.048) and 15.29% (P=0.054), respectively. This produced an average optimum SID Trp:Lys ratio of 15.64%. The final study included the other dietary essential amino acids (EAA) at a higher level, and ADG and PUN improved as SID Trp:Lys ratios increased, yielding optima of 17.93% (P<0.001) and 16.17% (P=0.009). This averaged to an optimum SID Trp:Lys ratio of 17.05%. Overall, diet composition did not affect the Trp:Lys requirement of growing pigs, however, feeding the other EAA at higher levels resulted in a higher estimated optimum SID Trp:Lys ratio. The optimum SID Trp:Lys ratio is estimated to lie between 15.29% and 17.05%.

An improved understanding of nitrogen metabolism in the gastrointestinal tract of the pig is required in order to provide accurate estimates of nitrogen and amino acid (AA) bioavailability in feed ingredients and for adequate diet formulation. Research objectives were to estimate the extent of fermentative AA catabolism (FAAC) in the upper gut of pigs. Further objectives were to determine the impact of lower gut nitrogen absorption on measures of apparent ileal digestibility of AA and nitrogen, whole-body nitrogen balance, and urea kinetics in pigs fed a valine-limiting diet. It was determined that simple isotope dilution calculations are inappropriate for determining ileal ammonia flux and FAAC from a continuous infusion of labelled ammonia and urea. A static model with two-pools (blood urea and digesta ammonia) was then developed to determine possible value ranges for FAAC in the upper gut of pigs. Maximum estimated FAAC based on this model was lower when dietary protein content was decreased (P < 0.001). The model presented is limited to minimum and maximum estimates of FAAC due to the sampling and isotope infusion protocol used. Refinements to the model and experimental protocol could allow for more accurate estimates of FAAC. Infusion of casein or urea into the lower gut of pigs did not affect measures of apparent ileal digestibility of AA or nitrogen. These results further validate the methodology available for determination of ileal digestibility and the use of ileal digestibility to estimate bioavailability of AA and nitrogen. Infusion of casein or urea into the lower gut resulted in an increase in nitrogen balance and urea flux in growing pigs fed a valine-limiting diet. Nitrogen absorbed from the lower gut of pigs is likely in the form of ammonia which is converted to urea. Lower gut nitrogen can contribute to whole-body protein deposition via urea recycling and microbial AA production in the upper gut. Lower gut nitrogen absorption should be accounted for when estimating bioavailability of nitrogen in feeds and foods. / Ontario Ministry of Agriculture, Food, and Rural Affairs (OMAFRA); Ontario Pork; Canadian Swine Research and Development Cluster; Natural Sciences and Engineering Research Council of Canada (NSERC); Evonik Industries AG

Made available in DSpace on 2017-07-10T17:47:55Z (GMT). No. of bitstreams: 1 Carolina_Natali_Langer.pdf: 3347830 bytes, checksum: e0c654ce879cbbab0be9d34b37c74f3d (MD5) Previous issue date: 2013-07-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The proposed objectives in this study were the metabolizable energy (ME) prediction of corn, sorghum and wheat bran from the chemical and energy composition of these foods in national and international literature data; the stepwise procedure validation of regressive selection by bootstrap simulation; the ME determination of these foods for growing pigs and subsequent validation of equations estimated in ME values observed in the experiment, using the bootstrap resampling procedure. For the ME prediction in chemical composition function, we used data from trials of pig metabolism and chemical composition of corn, sorghum and wheat bran, available in national and international scientific literature. Five models of multiple linear regression were adjusted to estimate the ME. In the stepwise procedure validation of regressive selection, it was used the non-parametric bootstrap resampling method, with each sample replacement, from the database formed via meta-analysis. It was observed the significance percentage by regressive (SPR) and the joint occurrence percentage of the model regressive (JOPMR). In the complete model and in the model without the digestible energy inclusion (DE), the DE and the gross energy (GE) were the regressive which presented the highest SPR (DE = 100% and GE = 95.7%), respectively, suggesting the importance of such regressive to explain the ME of energetic foods for pigs. However, the JOPMR were low, with values among 2.6 and 23.4%, indicating a low reliability of the predicted models to estimate the ME of corn, sorghum and wheat bran for pigs. Based on the SPR, the regressive of the models ME4 = 3824.440 - 105.294Ash + 45.008EE - 37.257DA1*CP (R2 = 0.90); ME5 = 3982.994 - 79.970Ash - 44.778DA1*CP - 43.416DA2*Ash (R2 = 0.92) are valid to estimate the ME of energetic food for pigs. In the field trial, we used 44 crossbred pigs, male and castrated, with an average initial weight of 24.3 ± 1.12 kg, in a randomized block experimental design, with ten treatments and a reference ratio. The ten treatments consisted of six corn and two sorghum cultivars, which replaced in 30% the RR, and two wheat brans, which replaced 20% of the RR. The method of total collection of feces and urine was used for determining the ME of food by using ferric oxide as a fecal marker to define the beginning and end of the collection period. The ME values of corn, sorghum and wheat bran for pigs vary from 3.161 to 3.275, from 3.317 to 3.457 and from 2.767 to 2.842 kcal kg-1 of natural matter, respectively. The validation of the ME prediction models was performed through adjusting the linear regression models of 1st degree from the observed values experimentally determined in function of ME predicted values, calculated by replacement of chemical and energetic composition values of foods, determined in laboratory, in the estimated models via meta-analysis, using the ordinary minimum squares method. The validation of 1st degree models and prediction models of ME was verified by testing the joint null hypothesis for the linear regression parameters (H0: β0 = 0 and β1 = 1). The crossvalidation percentage of each estimated model was evaluated by the same validation tests described in the single test validation. The model ME1 generated similar predicted EM values (p>0.05) to the experimentally observed ME values for national corn and sorghum cultivars in single test validation and had the highest percentage of validation (68%) in 200 bootstrap samples. The other models had a low percentage of cross-validation (0 to 29.5%), and the validated model by both procedures, and that can be used for national corn and sorghum is the ME1 = 2.547 + 0.969DE / Os objetivos propostos neste trabalho foram a predição da energia metabolizável (EM) do milho, sorgo e farelo de trigo a partir da composição química e energética desses alimentos em dados de literatura nacional e internacional; a validação do procedimento stepwise de seleção de regressoras por simulação bootstrap; a determinação da EM desses alimentos para suínos em crescimento e a subsequente validação das equações estimadas nos valores de EM observados no experimento, com utilização do método de reamostragem bootstrap. Para a predição da EM em função de composição química, foram utilizados dados de ensaios de metabolismo de suínos e de composição química do milho, sorgo e farelo de trigo, disponibilizados na literatura científica nacional e internacional. Foram ajustados cinco modelos de regressão linear múltipla para estimar a EM. Na validação do procedimento stepwise de seleção de regressoras, utilizou-se o método de reamostragem bootstrap não paramétrico, com reposição de cada amostra, a partir do banco de dados formado via metaanálise. Foi observado o percentual de significância por regressora (PSR) e o percentual de ocorrência conjunta de regressoras do modelo (POCRM). No modelo completo e no modelo sem inclusão de energia digestível (ED), a ED e a energia bruta (EB) foram as regressoras que apresentaram os maiores PSR (ED = 100% e EB = 95,7%), respectivamente, sugerindo a importância de tais regressoras para explicar a EM de alimentos energéticos para suínos. Entretanto, os POCRM apresentaram-se baixos, com valores entre 2,6 e 23,4%, indicando uma baixa confiabilidade dos modelos preditos para estimar a EM do milho, sorgo e farelo de trigo para suínos. Com base no PSR, as regressoras dos modelos EM4 = 3824,44 - 105,29MM + 45,01EE - 37,26DA1*PB (R2 = 0,90) e EM5 = 3982,99 - 79,97MM - 44,78DA1*PB - 43,42DA2*MM (R2 = 0,92) são válidas para estimar a EM de alimentos energéticos para suínos. No experimento de campo, foram utilizados 44 suínos mestiços, machos e castrados, com peso médio inicial de 24,3 ± 1,12 kg, em delineamento experimental de blocos ao acaso, com dez tratamentos e uma ração referência (RR). Os dez tratamentos consistiram em seis cultivares de milho e dois de sorgo, que substituíram em 30% a RR, e dois farelos de trigo, que substituíram em 20% a RR. O método da coleta total de fezes e urina foi utilizado para determinação da EM dos alimentos. Os valores de EM dos milhos, sorgos e farelos de trigo para suínos variam de 3.161 a 3.275, de 3.317 a 3.457 e de 2.767 a 2.842 kcal kg-1 de matéria natural, respectivamente. A validação dos modelos de predição da EM foi realizada por meio do ajuste de modelos de regressão linear de 1º grau dos valores observados determinados em ensaio sobre os valores preditos de EM, calculados por substituição dos valores de composição química e energética dos alimentos, determinados em laboratório, nos modelos estimados via meta-análise, utilizando-se do método dos mínimos quadrados ordinários. A validação dos modelos de 1º grau e dos modelos de predição da EM foi verificada por meio de teste da hipótese de nulidade conjunta para os parâmetros da regressão linear (H0: β0 = 0 e β1 = 1). O percentual de validação cruzada de cada modelo estimado foi avaliado por meio dos mesmos testes de validação descritos no teste único de validação. O modelo EM1 gerou valores de EM predita semelhantes (p>0,05) aos valores de EM observados em experimento para milhos e sorgos nacionais em teste único de validação e apresentou o maior percentual de validação (68%) em 200 amostras bootstrap. Os demais modelos tiveram baixo percentual de validação cruzada (0 a 29,5%) e o modelo validado por ambos os procedimentos, e que pode ser utilizado para o milho e sorgo nacionais é o EM1a = 2,547 + 0,969ED

Dans les régions tropicales. Il existe une multitude de systèmes alternatifs avec une grande diversité de pratiques. Ces systèmes sont souvent basés sur une utilisation optimale des ressources animales et végétales locales présentes sur l'exploitation. L'objectif de ce travail est de mieux connaître certaines de ces ressources tropicales disponibles et pouvant potentiellement être intéressantes à utiliser en alimentation porcine dans le cadre de ces systèmes alternatifs de type polyculture - élevage. Les résultats montrent que la capacité d'Ingestion des feuilles de manioc et de patate douce est la même quel que soit la forme de présentation (feuilles fraîches ou en farine). La capacité d'ingestion des feuilles de madère est plus élevée lorsqu'elles sont distribuées en farine (95 vs.40SgIj), inversement, les feuilles fraîches d'érythrine sont mieux ingérées (246 vs. 488 g/j). Les résultats sur la valeur nutritionnelle des feuillages tropicaux montrent qu'ils ont une faible densité énergétique comprise entre 6.5 et 8.2 MJ/kg de MS. La détermination du profil en acides aminés des feuilles montrent que les acides aminés des feuilles de madère et de patate douce sont plus digestibles que ceux des feuilles d'érythrine et de manioc.Au final les teneurs en lysine digestible sont de 5,3 g/kg MS pour la patate et 6,3 g/kg MS pour le madère. En conclusion, l'ingestion, ainsi que la teneur énergétique et protéique des feuilles d'une feuille à l'autre varie en fonction de sa teneur en fibres mais également en fonction de leur concentration en tanins. En pratique, les feuilles de patate douce et de madère sont les plus intéressantes pour la réalisation de ration. / In the troples, there are a multitude of alternative systems with wide variety of practices. These systems are often based on an optimal use of local plantand animal on the farm. The objective of this work is to better understand some of these tropical resources avaibable and can potentially be interesting to use in pig feed in the context of these mixed farming system.The results show that the feed intake capacity of cassava and sweet potato leaves is the same whatever the processing form (fresh leaves or meal).The intake capacity of cocoyam leaves18 higher when distributed Into meal (95 vs.408g1d). In opposite the Erythrina fresh leaves are best Ingested (246 va, 488 g 1dl. Results on the nutrltlonal value of tropical foliage show they have low energy density between 6.5 and 8.2 MJ1kg DM. The determlnation of amino acid profile show that the amina acids of cocoyam and sweet potato leaves are more dlgestible than the erythrina and cassava leaves. Ultlmately digestible lysine contents were 5.3 g/kg DM for potato and 6.3 g / kg DM for the cocoyam. ln conclusion, ingestion, and energy and protein content of leaves from one sheet to another depends on its fiber content but aIso according to their tannin. In practice,the leaves of sweet potato and cocoyam are the most Interesting for the realization of diet

The objectives of the research were to examine the effects of high dietary levels of fibrous feeds, and of supplementation with Roxazyme® G2 (RX), on the digestive metabolic and physiological responses of growing pigs fed maize-soybean diets. The nutrient and dietary fibre (DF) composition, the swelling and water-binding capacities of maize (MM), its hominy chop (HC) and cobs (MC), dehulled soybean (dSBM) and the hulls (SH), brewer’s grains (BG), lucerne hay (LH) and wheat bran (WB) were evaluated using standard procedures. Feed fibre fractions were isolated by simulating upper tract digestion in an Ankom® DaisyII Incubator, whereby each feed was digested in pepsin (porcine, 200 FIP-U/g, Merck No, 7190), followed by pancreatin (porcine, grade IV, Sigma No P-1750), with recovery of the fibrous residues. In a third step to complete the simulated pig gastro-intestinal digestion, the pepsin-pancreatin fibre extracts were digested by RX or Viscozyme L ® V2010 (VZ). Enzyme activity was measured as the coefficients of partial degradability (solubilisation) of the washed fibre extracts. The kinetics and products of fermentation of the DF were evaluated in an AnkomRF gas production system, using buffered faecal inoculum. Among the feed ingredients, dissimilar, fibre source-dependent activities between RX (0.02 to 0.12) and VZ (0.04-0.33) were observed. The lowest RX activities were observed on the maize and soybean derived fibres, with similarly low VZ activity on MC fibre. Variation in the activity of faecal microbial enzymes was similarly indicated by the variable production of fermentation gas (51.8-299.4 mL g-1 DM) and short chain fatty acids (SCFA) (2.3-6.0 mMol g-1 DM). Soy hull, dSBH, MM and HC fibres were highly fermentable, with low fermentability of BG, MC and WB fibres. The fibres differed in the composition of fermentation SCFA, whereby SH, LH and MC shifted fermentation to Ace, and BG, dSBM, WB, MM, HC favoured Pro, while MM and HC favoured But production. The same nutritional properties were similarly evaluated in complete diets which were formulated from the ingredients for growth, and metabolic trials. For the growth trial, a standard (STD) (control), 141 g total dietary fibre (TDF) kg-1 dry matter (DM) maize-soybean growing pig diet, and five iso-nutritive, 246 g TDF kg-1 DM nutritionally balanced diets were formulated. The high DF was achieved by partial replacement of the MM and dSBM in the STD diet with MC, SH, BG, LH or WB. The differences in RX and VZ activities and in the fermentation characteristics which were observed on the fibre extracts from the high fibre ingredients were reflected in the DF from the respective complete diets in which they were included. However, the fibre from the basal dietary ingredients reduced the absolute values and the variation in the activities of RX (0.03-0.06) and VZ (0.16-0.22), and similarly reduced the variation in gas (126.6-187.6 mL g-1 DM) and SCFA (4.1-5.4 mMol g-1 DM) production of the DF from the fibrous diets. Enzyme activities on the STD DF were low for RX (0.03) and high for VZ (0.25). The STD DF produced 205.3 mL gas g-1 DM, which was similar to SH DF, and higher than all the other diets. The STD DF produced 5.0-mMol SCFA g-1 DM, which was quantitatively, and not statistically higher than the other fibres. The composition of SCFA was similar across all diets, except for the high percent Ace, with low Pro by the SH DF. Compared to the STD, the high DF diets increased percent Ace, with reduced Pro and But. The STD, MC, SH, BG, LH and WB diets were each prepared in duplicate mixes, one of which was fortified with 200 mg RX kg-1 feed (as fed). Seventy-two intact Large White X Landrace, male, 32.0 ± 5.6 kg live weight (LW) pigs were allocated to the diets in two completely randomised weight blocks in a 2 (fibre source) X 2 (enzyme) factorial arrangement. The pigs were fed ad libitum for 10 weeks. Cumulative LW gain and feed intake were measured at different stages of growth, and at slaughter. Apparent total tract digestibility (ATTD) of nutrients was estimated at 65-70 kg LW, using 0.2% (as fed) chromium oxide as the indigestible marker. Ileal tissue was sampled 50 cm above the ileo-caecal valve, on which villi height and area, and crypt depth were evaluated by computerised image analysis. Blood was sampled at slaughter from the severed vena jugularis, 16 hours after feeding. Serum urea, creatinine, triglycerides, glucose, and total cholesterol were analysed chemically. The serum metabolome was further explored using Proton Nuclear Magnetic Resonance Spectroscopy (1H -NMRS). There was fibre X RX interaction for villi height, whereby the enzyme reduced the villi height in pigs on the SH, STD and WB diets, with an opposite effect on pigs on the MC, BG, LH diets. The soluble fibre content was negatively correlated with crypt depth. Chemical analysis did not detect differences in metabolite concentration between the STD and the high fibre diets. However, more serum cholesterol was observed in pigs fed the WB compared to the LH and MC diets. 1H-NMRS indicated that feeding pigs the WB diet increased serum Cys and His, while supplementation of RX increased serum formate, glucose, and urea. There was diet X enzyme interaction for fructose, glucose, Arg, Cys, Ser, and Trp, whereby RX increased the levels in pigs on MC and WB, with an opposite effect in pigs on the other diets. There was large DF source-dependent variation among diets in ATTD of DM (0.80-0.85), organic matter (OM) (0.81-0.87), gross energy (GE) (079-0.85) and CP (0.81-0.85), whereby, relative to the STD diet, high DF reduced the ATTD of DM (all diets except SH), organic matter (OM) and energy and CP (all diets except the MC). Positive correlation was observed between fermentability and the ATTD digestibility of DM, OM, energy, ADF, NDF, and fat. Negative correlation was observed between the swelling capacity and the ATTD of DM, OM, energy and protein, between DF solubility and DM, OM, protein, ADF and NDF, and between water binding capacity and ATTD of DM and OM, energy and NDF. At slaughter, there was similarly large, and DF source-dependent variation among the high fibre diets in feed intake (2.31-2.71 kg as fed day-1), live weight gain (0.75-0.86 kg day-1), and feed: gain ratio (2.73-3.00). Corresponding values for the STD diet were 2.44 kg day-1, 0.83 kg day-1and 2.86 kg day-1, respectively. Relative to the STD, LH reduced feed intake and live weight gain, and MC increased the feed: gain ratio. Predictions based on the in vitro fermentability of DF and feed intake suggested that due to poor fermentability, and or restriction of feed intake, relative to a standard fibre diet, high dietary levels of MC, WB and BG may reduce fermentation in the lower gut, while similar dietary levels of SH and LH may result in substantial increases in fermentation. At 50 kg LW, the fermentability of DF was positively correlated with feed intake and with weight gain, while water binding capacity and solubility of DF were negatively correlated with feed intake. At slaughter, the solubility of DF was negatively correlated with feed intake and feed: gain ratio. Large variation among the high fibre diets was also observed in the slaughter weight (89.2-96.8 kg), dressing % (68.6-76.4), meat colour (80.4-82.3), lean % (69.5-71.2), and fat % (10.1-12.6). In comparison, pigs on the STD diet scored 94.7 kg slaughter weight, 75.1% dressing, 81.6 cm carcass length, 82.5 meat colour, 68.4% lean, and 15.0% fat. Relative to the STD, LH reduced dressing and fat %. Lucerne hay and WB increased the lean%. For the metabolic trial, two iso-nutritive, mixed high fibre (319 g TDF kg-1 DM), nutritionally balanced diets were formulated to contain DF of high (HF) versus low (LF) fermentability. The diets had similar content of soluble DF and similar swelling and water binding capacities. Viscozyme was more active than RX on both the HF (0.20 versus 0.04) and the LF (0.17 versus 0.07) DF. The combination of RX and VZ statistically increased the enzyme activity on the HF (0.25) and quantitatively increased enzyme activity on the LF (0.18) DF, suggesting additive or synergistic effects. More gas was produced by the HF (159.5 mL g-1 DM) compared to the LF DF (96.6 mL g-1 DM). More SCFA were produced by HF (5.0 mMol g-1 DM), compared to the LF DF (3.6 mMol g-1 DM). Compared to the STD, HF DF increased percent Ace, with reduced Pro and But. The LF DF increased percent Ace, with quantitative, and not statistical reduction of Pro and But. In a metabolic trial, the HF and LF diets, and their duplicates containing 0.270 g RX kg-1 DM of feed (as fed) were fed ad libitum to eight ileum T-cannulised, intact Large White X Landrace male pigs weighing 65.0 ± 5.1 kg. The diets were allocated to the pigs in a duplicate 4 x 4 Latin Square design, in a 2 (enzyme) x 2 (fermentability) factorial arrangement. Each period consisted of two weeks of adaptation followed by five days of sampling. The ileal digesta was collected in each period and was similarly subjected to the fermentation test. Apparent ileal digestibility (AID) and ATTD were determined using 0.2% (as fed) chromium oxide as the indigestible marker. N excretion in faeces and urine were measured, and N retention was calculated. Blood was sampled by vena jugularis puncture on the last day of each period. Two blood samples were collected, the first 15 hours after removal from feed (15-hour serum), and the second 3 hours after re-introduction to feed (3-hour serum). Serum metabolites were evaluated by both chemical analyses and by 1H-NMRS, as described for the growth trial. Roxazyme did not affect the fermentation characteristics of the ileal digesta. In similar proportion to the fermentability of the PP digesta, the HF ileal digesta was more fermentable (65.4 mL gas g-1 DM and 6.1 mMol SCFA g-1 DM) than the LF ileal digesta (46.7 mL gas g-1 DM and 4.4 mMol SCFA g-1 DM SCFA). Prediction based on the in vitro fermentability of DF and feed intake suggested the HF diet could support one half times more fermentation in the lower gut compared to the LF diet. The HF diet had higher AID of DM (62.5 vs. 58.6), OM (65.6 vs. 62.1), energy (64.4 vs. 61.0), fat (85.8 vs. 81.7) and ash (41.8 vs. 32.7). The AID of HO-Pro, Met and Val were higher for the LF diet. There was diet X enzyme interaction on the AID of Met, whereby the RX reduced the AID of met in the LF diet, and not that of the HF diet. The ATTD was higher for the HF diet for DM (74.2 vs. 68.4), NDF (64.7 vs. 57.4), and ADF (35.1 vs. 21.0). There was positive correlation between the fermentability of DF and the AID DM, OM, ash, ash, fat and energy. The solubility of DF was negatively correlated with the AID of DM, OM, ash, fat, ADF and energy, and with the ATTD of DM, OM, ash, fat, energy, NDF, and ADF. Negative correlation was also observed between the swelling capacity of DF and the AID of protein, Trp and Lys. The solubility of DF was positively correlated with Ser, Ala, Val, Iso-Leu and His. There was diet X enzyme interaction for urea in the 15- hour serum, whereby RX tended to reduce the urea in the LF diet, while it increased that of the HF diet. Fermentability negatively correlated with urea in the 15- hour serum, and positively correlated with serum glucose in the 3-hour serum. In the 3-hour sample, 1H-NMRS indicated higher fucose, Pro and cholesterol in the LF diet. 1H-NMRS also indicated fermentability x RX interaction for Ser, Tyr, Lys, creatine, and possibly, glucose or fructose, glycerol or Gly and His or Arg, whereby RX increased the levels in the LF diets, with opposite effect in the HF diet. In conclusion, enzyme activities and fermentability were higly variable among different DF sources, and the effects were evident in the fibrous complete diets. The results of the in vitro studies supported the application of the methods to formulate fermentable insoluble fibre-rich, maize-soybean-mixed co-product diets. Correlation analyses suggested that DF fermentability, and solubility, swelling and water binding capacities explained significant proportions of the variances of the metabolic and physiological responses of the pigs to different feeds. Predictions based on the in vitro fermentability of DF and feed intake suggested that a strategy whereby pig diets are enriched in DF after the feedstuffs are screened on DF fermentability could substantially increase fermentation in the lower gut. Overall, the results suggested that productivity can be maintained in growing pigs fed diets containing up to twice the standard levels of DF, provided producers target co-product feeds that contain highly fermentable DF. The use of RX to improve nutrient digestion and to stimulate gut fermentation was not justified. / Environmental Sciences / Ph.D. (Environmental Sciences)