L’aulacode (Thryonomys swinderianus) est un rongeur herbivore récemment domestiqué en Afrique pour la production de viande. Quelques études antérieures ont portés sur l’alimentation de cet animal, dans le but d’améliorer la productivité des élevages. A ce jour, nos connaissances sur la digestion et les besoins nutritionnels de cet animal sont encore très parcellaires. Le premier objectif de notre étude était d’améliorer nos connaissances sur la physiologie digestive de l’aulacode en croissance, en particulier en relation avec les apports de fibres alimentaires, avec pour finalité de proposer des recommandations nutritionnelles en fibres pour optimiser la croissance et la santé digestive de cet animal. Notre second objectif était d’analyser les effets d’une diminution du ratio protéines digestibles / énergie digestible parallèlement à une hausse des apports d’amidon, sur la digestion et les performances. La finalité était d’analyser les possibilités de formuler un aliment complet moins onéreux pour les éleveurs et qui respecte les besoins de l’aulacode en croissance. Notre étude a permis de savoir que le caecum est le compartiment digestif le plus important du jeune aulacode entre 1 et 3 mois d’âge, avec plus de 40% du contenu digestif total. L’activité microbienne caecale (100 mM d’acides gras volatils totaux (AGVt) par gramme de contenu frais) est élevée, et similaire à celle des ruminants ou d’autres herbivores monogastriques. Le profil fermentaire est caractérisé par une prédominance de l’acétate (75 % des AGVt) et un ratio propionate / butyrate supérieur à 1. Le pyroséquençage 454 de l’ADN16S bactérien a permis de caractériser le microbiote caecal. Au sevrage, nous observons une prédominance du phylum des Bacteroidetes, avec 51 % d’abondance relative, alors que le phylum des Firmicutes devient majoritaire (50%) à 3 mois d’âge. Le microbiote caecal est caractérisé par la présence de genres souvent identifiés dans d’autres écosystèmes digestifs d’herbivores, tels que : RC9 (2 à 8%), Parabacteroides (1 à 8%), Prevotella (3 à 6%) et Xylanibacter (1%), Erysipelotrichaceae Turicibacter (1 à 7%), Lachnospiraceae Incertae_Sedis (4 à 5%), Ruminococcaceae Incertae_Sedis (1 à 2%) et Ruminococcus (1 à 3%). D’autres genres, absents chez des espèces voisines comme le lapin et le cobaye, semblent plus spécifiques de l’aulacode, tels que Termite_Treponema_cluster (1.7 à 2.2%) et Treponema (7 à 13%), du phylum des Spirochaetes. L’analyse des performances zootechniques indique qu’un taux de fibres compris entre 17 et 21 % d’ADF représenterait un bon compromis entre santé digestive et croissance de l’aulacode après son sevrage. Descendre au dessous de 6 g de protéines digestibles par MJ d’énergie digestible, via une hausse importante des apports d’amidon et une baisse importante du taux de protéines brutes (en dessous de 11 %) et de fibres, est préjudiciable à la croissance des animaux. / The cane rat or grasscutter (Thryonomys swinderianus) is a rodent herbivore recently domesticated in Africa for meat production. Some previous studies focused on the feeding of this animal, in order to improve the productivity of farms. To date, our knowledge of digestion and nutritional requirements of this animal are still very scarce. Our first objective was to improve our knowledge of digestive physiology of the young grasscutter, particularly in relation to dietary fibre supply, in order to improve the recommendations for dietary fibre content of diets to optimize growth and digestive health. Our second objective was to analyze the effects of a decreased digestible protein / digestible energy ratio, along with an increased intake of starch, on digestion and performances. The final aim was to analyze the possibilities to formulate a complete feed, cheaper for farmers and that meets the requirements of the young grasscutter. Our study found that the caecum is the most important digestive compartment of the young grasscutter between 1 and 3 months of age, with more than 40% of the total gut contents. The caecal microbial activity (100 mM of total volatile fatty acids (VFA) per gram of fresh content) is high and similar to that of ruminants or other herbivorous monogastric animals. The fermentation profile is characterized by a predominance of acetate (75% of total VFA) and a propionate / butyrate ratio greater than 1. A pyrosequencing of bacterial 16S-DNA was used to characterize the caecal microbiota. At weaning (one month), we observe a predominance of the Bacteroidetes phylum, with 51% of relative abundance, whereas the Firmicutes phylum becomes predominant (50%) at 3 months of age. Caecal microbiota is characterized by the presence of genera often identified in other digestive ecosystems of herbivores, such as: RC9 (2-8%), Parabacteroides (1-8%), Prevotella (3.6%) and Xylanibacter (1%), Erysipelotrichaceae Turicibacter (1-7%), Lachnospiraceae Incertae_Sedis (4-5%), Ruminococcaceae Incertae_Sedis (1-2%) and Ruminococcus (1-3%). Other genera, absent in related species such as rabbits and guinea pigs, seemed more specific of the grasscutter, such as Termite_Treponema_cluster (1.7-2.2%) and Treponema (7-13%) of the Spirochaetes phylum. The analysis of growth performances indicated that a dietary fibre content between 17% and 21% of ADF represents a good compromise between digestive health and growth of the grasscutter after weaning. Decreasing below 6g of digestible protein / MJ of digestible energy, via a high increase in starch intake and a significant decline in crude protein content (below 11%) and fibre, is detrimental to the growth of animals.

La dégradation des fibres alimentaires est une fonction essentielle des écosystèmes digestifs microbiens. Chez le ruminant, elle est assurée par des bactéries, champignons et protozoaires capables de produire de nombreuses enzymes nécessaires à l’hydrolyse des polysaccharides de paroi végétale. Parmi les facteurs susceptibles d’influencer l’efficacité de dégradation des fibres, qui est une composante importante de la productivité et de la santé animales, des additifs tels que des levures probiotiques apparaissent comme un levier intéressant. Afin d’approfondir les connaissances sur les facteurs de modulation de l’activité fibrolytique, une biopuce ADN fonctionnelle, outil moléculaire haut-débit, ciblant les gènes codant les enzymes clés de la dégradation de la cellulose et des xylanes dans les écosystèmes digestifs a été développée. Aussi, une méthode efficace dédiée à des échantillons ruminaux pour la soustraction des ARNr à partir des ARN totaux a été mise au point afin d’accroitre la sensibilité de l’outil. La biopuce fonctionnelle a été validée sur échantillons de complexité croissante et démontre d’excellents caractères de spécificité et de sensibilité tout en étant exploratoire et quantitative. Des régulations différentielles de l’arsenal des gènes de la fibrolyse de la bactérie du rumen Fibrobacter succinogenes ont pu être montrées. De même, les résultats sur échantillons de rumen suggèrent un rôle des microorganismes eucaryotes dans la fibrolyse pouvant être plus important qu’initialement envisagé. Cette approche métatranscriptomique dirigée pourra in fine continuer d’être appliquée dans l’étude de l’impact de facteurs biotiques et abiotiques sur la fonction fibrolytique microbienne chez les animaux d’élevage. / Dietary fibre degradation is an essential function of microbial digestive ecosystems. In ruminants, this function is ensured by bacteria, fungi and protozoa, producing a large array of enzymes able to degrade plant cell wall polysaccharides. Among factors likely to influence the efficiency of fibre degradation, which is an important component in animal productivity and health, dietary additives such as probiotic yeasts appear as an interesting tool. To provide more insight on factors modulating fibrolytic activity, we designed a functional DNA microarray targeting genes coding for key enzymes involved in cellulose and xylan degradation by digestive microbiota. Also, an efficient method dedicated to rumen samples for removing microorganisms’ rRNA from total RNA samples was developed to increase the sensitivity of the tool. The DNA microarray was validated using targets of increasing complexity and demonstrated sensitivity and specificity as well as explorative and quantitative potential. Differential expression of genes involved in fibrolysis was evidenced in the rumen bacterium Fibrobacter succinogenes. Moreover, results on rumen samples suggest a more important role of eucaryotes in fibre degradation than previously thought. This targeted metatranscriptomic approach will be further applied to the study of the impact of biotic and abiotic factors on the microbial mechanisms of fibre degradation in livestock.

ABSTRACT Influence of fenugreek gum on bread and in vitro physiological effects Keisha T. Roberts Advisors: University of Guelph Dr. S.W. Cui Professor T.E. Graham This thesis examined the effect of fenugreek gum, from Canadian grown fenugreek on bread quality, when substituted for wheat flour at 5 % and 10 %, and the in vitro physiological effects of these breads, based on models of acute and long - term feeding. Study I determined bread could be produced with 10 % fenugreek gum, while maintaining quality parameters of volume and texture, comparable to a control. This was accomplished through the development of a novel bread production method, using the lamination procedure for puff pastry production. The behavior of fenugreek gum and starch (wheat flour) was determined by rapid visco analysis (RVA), farinograph and dynamic rheological measurement, while scanning electron microscopy of bread found fenugreek gum could be identified within the bread matrix. Study 2 in vitro starch digestion found fenugreek gum at 5 % and 10 % reduced glucose liberated from bread, with 10 % fenugreek gum causing a reduction of over 30 %. RVA of fenugreek breads highlighted differences in viscosity between breads and wheat flour substituted with the gum. This was substantial as viscosity measurements by RVA are conducted on raw ingredients and not the food as consumed, which reflects the possible reduction in viscosity with food processing. This study also determined extruding fenugreek gum may have caused morphological changes to the gum, which may possibly contribute to attenuation of glucose liberated in vitro. Study 3 evaluated the accumulation of short chain fatty acids (SCFA) from the fermentation of three substrates: Extruded fenugreek gum, bread with 10 % extruded gum and control bread, based on fecal microbiota from three donors. SCFA profiles varied with substrates and donors, with fenugreek gum having the highest accumulation of SCFA after 12 hours. Donors were a caucuasian Canadian, a black Jamaican and a black Trinidadian who was the only donor culturally exposed to fenugreek. This Trinidadian’s SCFA profiles were consistently higher for fenugreek gum than the other donors. These studies collectively showed fenugreek gum, though viscous could be successfully incorporated into bread and have potential as a functional food and nutraceutical.

Cardiovascular diseases are the leading cause of death in most industrialised countries and in developing countries the trend in cardiovascular-related deaths is increasing. World-wide, type 2 diabetes mellitus (T2DM) is an emerging cause of disability and premature death. Both these conditions are closely associated with the consumption of energy-dense foods and food products that are poor in nutrients, as well as with a sedentary lifestyle. Pharmacological and surgical interventions can improve the outcome and delay the progression of the disease, but in terms of population-level prevention there is no substitute for the adoption of a healthy lifestyle. SETTING The underlying studies were conducted in Västerbotten (the VIP study), and in Norrbotten and Västerbotten combined (the MONICA Project). Norrbotten andVästerbotten are the two northernmost counties in Sweden. Since the mid-1980sthe prevalence of cardiovascular disease has decreased and diabetes rates haveremained stable in this region, despite of an unbroken trend of increasing body weight. OBJECTIVE The aim of this thesis is to describe changes in reported dietary habits, estimatetheir relative importance as risk factors for diabetes and cardiovascular disease, and finally to identify lifestyle components as potential targets for intervention. RESULTS The first paper describes changes in self-reported food consumption between 1986 and 1999. During this period, the population in question switched from products with high saturated fatty acid content (e.g. milk containing 3% fat, butter) to foods containing less saturated fat (e.g. milk containing 1.5% fat, vegetable oil, low-fat margarine); pasta and rice were consumed more often, and potatoes were consumed less. Convenience foods (e.g. hamburgers, snacks, sweets) became more popular, whilst traditional dishes (e.g. potato dumplings, black pudding, blöta) decreased in popularity. Fruit and vegetable intake remained low. In paper two we study the effects of these changes in food intake on the risk of developing T2DM using body fat distribution as an early indicator. Increased consumption of convenience foods was associated with unfavourable changes (smaller hip circumference and larger waist circumference), whereas the increased consumption of vegetable oil and pasta was associated with low-risk fat distribution. In the third paper we report studies on the association between fat consumption and T2DM. We used the pattern of fatty acids in the membranes of red blood cells as a marker of fat intake. In addition to confirming earlier findings (markers of the intake of saturated fat are associated with increased risk of T2DM and markers of unsaturated fat are associated with reduced T2DM risk), we also identified associations between two markers of milk-derived saturated fat intake and enterolactone, a biomarker of dietary fibre intake, and the risk of developing myocardial infarction. Our results indicate that moderately high levels of enterolactone intake in men are associated with lower risk of experiencing myocardial infarction. Manuscript 5 ranks education level, physical activity, smoking status, and self-reported intake of dietary fibre and fatty acids according to their effects on body fat distribution. Increased levels of physical activity, a higher education level and a reduced intake of saturated fat from meat were ranked as the most strongly associated factors in both men and women. Increased intake of dietary fibre from grains in women, and increased intake of dietary fibre from fruits and vegetables in men, was also inversely associated with average waist circumference. CONCLUSION Both questionnaire-based and biological markers of the risk of developing diabetes or cardiovascular disease have been identified. Based on available population level measurements, reduced consumption of convenience foods, increased consumption of whole-grain products, fruits and vegetables, vegetable oil and pasta as well as increased physical activity are potential goals for interventions in northern Sweden.

The ability of the soluble fibre (1->3)(1->4)-β-D-glucan to attenuate postprandial glycemic responses depends on its viscosity which, in turn, depends on molecular weight (MW) and dose. However, the effect of altering viscosity by changing solution volume is unknown. Furthermore, β-glucan solutions may form hard gels when left to age, but the effect of these gels on glycemic responses is unknown. Therefore, the effects of varying the MW and volume of β-glucan solutions and hard gels, on glycemic responses were determined. The results showed that glycemic responses were reduced by increasing viscosity by increasing MW but not by reducing solution volume. Although β-glucan gels reduced the rate of glucose diffusion in vitro, they had no effect on glycemic responses in vivo. Thus, changing solution viscosity through changes in volume does not alter the effect of β-glucan on glycemic response, and β-glucan gels are ineffective at attenuating in vivo glycemic responses.

The ability of the soluble fibre (1->3)(1->4)-β-D-glucan to attenuate postprandial glycemic responses depends on its viscosity which, in turn, depends on molecular weight (MW) and dose. However, the effect of altering viscosity by changing solution volume is unknown. Furthermore, β-glucan solutions may form hard gels when left to age, but the effect of these gels on glycemic responses is unknown. Therefore, the effects of varying the MW and volume of β-glucan solutions and hard gels, on glycemic responses were determined. The results showed that glycemic responses were reduced by increasing viscosity by increasing MW but not by reducing solution volume. Although β-glucan gels reduced the rate of glucose diffusion in vitro, they had no effect on glycemic responses in vivo. Thus, changing solution viscosity through changes in volume does not alter the effect of β-glucan on glycemic response, and β-glucan gels are ineffective at attenuating in vivo glycemic responses.

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