Search

Magnetic resonance imaging and spectroscopy (MRI and MRS) are non-invasive methods that have the potential to estimate in vivo the quantity and the quality of abdominal adipose tissues (AT). The scientific and clinical context of this thesis is based on an overfeeding study entitled "Poly-Nut". One of the main objectives of this study is to analyze changes in adipose tissues in a rapid phase of weight gain. The originality and complexity of this thesis rely in the development, adaptation and comparison of several quantitative methods of MRI and MRS, for the study of lipid signal, in a clinical context, at 3T. The reliability and the validation of the measurements obtained in vivo using these techniques are the main subject of this PhD thesis. For the quantitative analysis of the spectroscopy signal, different existing methods have been compared to those developed specifically for our clinical study. According to the model function used, the nonlinear-least-squares parametric estimation applied to the lipid spectra can lead to an ill-posed nonlinear problem. We demonstrated that the use of a simplified model based on the structure of a triglyceride chain, as recently used in quantitative imaging, was a valid solution regarding the state of the art. Then different methods (MRI, MRS, Dual Energy X-ray absorptiometry, gas chromatography) were used to characterize the subcutaneous and visceral AT. We demonstrated the feasibility of MRI to follow the lipid content in the liver as well as the volume and the fatty acid composition of AT using a single multiple gradient-echo acquisition. Finally, experimental developments were carried out in parallel with the clinical study, on a 4.7T preclinical system, first, to compare different strategies for encoding the chemical shift using imaging and, secondly, to characterize MRS methods for in vivo estimation of the relative proportion of omega-3 among all fatty acids.; L’imagerie et la spectroscopie par résonance magnétique nucléaire (IRM et SRM) sont des méthodes non-invasives qui ont le potentiel d’estimer in vivo la quantité et la qualité des adiposités abdominales. Le contexte scientifique et clinique de ce manuscrit s’articule autour de l’étude de surnutrition « Poly-Nut » dont l’un des objectifs est d’analyser les évolutions des tissus adipeux (TA) dans une phase rapide de prise de poids. L’originalité et la complexité de cette thèse résident dans le développement, l’adaptation et la comparaison de plusieurs méthodes quantitatives d’IRM et de SRM, pour l’étude du signal lipidique dans un contexte clinique à 3T. La fiabilité et la validation des mesures obtenues in vivo par ces techniques font ici l’objet d’une étude approfondie. Pour l’analyse quantitative du signal de spectroscopie, différentes méthodes existantes ont été comparées à celle développée spécifiquement pour notre étude clinique. L’estimation paramétrique par moindres carrés non linéaires appliquée aux spectres RMN des lipides peut conduire, selon la fonction modèle utilisée, à un problème non linéaire mal posé. Nous montrons alors que l’utilisation d’un modèle simplifié se fondant sur la structure d’une chaine de triglycéride, comme utilisé récemment en imagerie quantitative, constitue une solution valide au regard de l’état de l’art. Ensuite différentes méthodes (IRM, SRM, Dual Energy X-ray absorptiometry, chromatographie en phase gazeuse) ont été utilisées pour caractériser les TA sous-cutanés et viscéraux. Le suivi par IRM du contenu lipidique du foie ainsi que du volume et de la composition en acide gras des TA à partir d’une unique acquisition en multi-écho de gradient est démontré. Enfin des développements expérimentaux menés parallèlement à l’étude clinique sur un imageur préclinique à 4,7T, comparent différentes stratégies d’encodage du déplacement chimique par imagerie et caractérisent des méthodes SRM pour estimer in vivo la proportion d’omégas-3 dans les chaînes d’acides gras.

1 página.--Trabajo presentado al Proceedings of the Fifth Dairycare Conference 2018, p. 21 (#9). Thessalonika (Grecia),19-20 de marzo de 2018., Requirements of high producing ruminants can only be covered by diets of high nutritive value that can induce subacute rumen acidosis (SARA), but not for all animals at the same time and with the same intensity. A challenge is to find noninvasive biomarkers to detect animals suffering from SARA. Milk fatty acids composition is a good candidate as it is partly linked to rumen metabolism. The aim of this work was to compare two methods of measure of milk fatty acids composition: gas chromatography (GC) considered as a “standard”, but a time-consuming and expensive method and medium infrared analysis (MIR), a rapid and cheap method which can be applied on field. Eight rumen cannulated dairy goats adapted to a low concentrate diet (20 %) were abruptly switched to a high concentrate diet (50 %). Samples of milk were taken individually on the morning for 2 days before the change, the 4 days following the change and once weekly for 3 weeks. 91 fatty acids were detected by GC and 58 were estimated by MIR. Rumen fluid was sampled simultaneously before the morning feed (T0) and 1, 2, 4 and 6 hours after. Rumen samples were analysed for pH and volatile fatty acid (VFA) composition. A principal component analysis (PCA) was used to examine the relationships among milk fatty acids percentages measured by GC. The projection of the saturated fatty acids on the first two components showed an opposition between the short and medium fatty acids (SMFA) up to 13C and the long (L) chain fatty acids (LFA). An index was calculated as the ratio of SMFA/LFA. It was positively linked to the pH values and negatively to [VFA] ones. A similar ratio was calculated from the MIR estimation. Even if both ratios were correlated (r = 0.60, n = 72), the MIR ratio was higher (0.72 ± 0.06) than the GC ratio (0.50 ± 0.05) and was not correlated with pH and only poorly with VFA. MIR overestimated SMFA and underestimated LFA. In conclusion, GC is a useful tool to detect SARA in dairy goats from milk composition, but MIR is not a relevant method due to the inaccuracy in the prediction of FA.

International audience; Ruminant diets usually contain low levels (2-3%) of lipids and fatty acids (FA). Before absorption, dietary lipids undergo extensive modifications by ruminal micro-organisms. These processes and FA absorption are described in detail in Chapter 11. In the present chapter, the origins of muscle FA are summarised in Figure 12.1. Muscle medium chain FA are synthesised de novo from plasma acetate and β-hydroxybutyrate to generate C12:0, C14:0 and C16:0. Long chain muscle FA arise from modified dietary lipids via plasma lipoproteins (C16:0, C18:0, C18:1, C18:2 and C18:3) and are taken up through the action of the lipoprotein lipase (LPL). All saturated FA (SFA, mainly C14:0, C16:0, C18:0) and C18:1 t11 can be desaturated by the stearoyl-coenzyme A desaturase (Δ9 desaturase, SCD) to produce C14:1 c9, C16:1 c9, C18:1 c9 and C18:2 c9t11. Both C18:2 n-6 and C18:3 n-3 are elongated and desaturated to longer n-6 and n-3 polyunsaturated fatty acids (PUFA): C20:4 and C22:4 for the n-6 PUFA and C20:5, C22:5 and C22:6 for the n-3 PUFA.

Despite the recent advances in transcriptomics, gene expression studies addressing cattle´s skeletal muscle adaptations in response to compensatory growth are warranted, particularly regarding lipid metabolism due to its impact in meat sensory and nutritional traits. In the present study, in comparison to ad libitum feeding, a period of feed restriction was used in order to understand the changes in bull´s lipid metabolism and gene expression of the adipogenic and lipogenic pathways after re-alimentation. Thus, 40 young Alentejana bulls were either fed ad libitum (CG group) from 9 to 18 months of age or subjected to food restriction from 9 to 15 months of age, and fed ad libitum until 24 months of age (DG group). The intramuscular fat (IMF) and total fatty acids (FA) contents were similar between groups. The major FA (>2%) contents were similar (16:0, 16:1c9, 18:1c9 and 18:2n-6) between treatments with the exception of 18:0 content that was 15% lower in DG than in CG and 20:4n-6 that tended to be greater on DG bulls. Regarding minor FA (

International audience; on diet, physiology, and feeding behaviour of fish within lakes. Overall, we found a low impact of parasitism on the physiological condition and trophic status of juvenile perch at the end of their first summer. We find instead that juvenile perch growth and fat storage, both factors tied to their winter survival, are under strong nutritional constraints. However, the coinciding nutritional constraints and parasite prevalence of perch juveniles in these three lakes may result from the indirect effect of lake nutrient concentrations, which, as a major control of zooplankton communities, simultaneously regulate both the dietary quality of fish prey and the host-parasite encounter rates.

Magnetic resonance imaging and spectroscopy (MRI and MRS) are non-invasive methods that have the potential to estimate in vivo the quantity and the quality of abdominal adipose tissues (AT). The scientific and clinical context of this thesis is based on an overfeeding study entitled "Poly-Nut". One of the main objectives of this study is to analyze changes in adipose tissues in a rapid phase of weight gain. The originality and complexity of this thesis rely in the development, adaptation and comparison of several quantitative methods of MRI and MRS, for the study of lipid signal, in a clinical context, at 3T. The reliability and the validation of the measurements obtained in vivo using these techniques are the main subject of this PhD thesis. For the quantitative analysis of the spectroscopy signal, different existing methods have been compared to those developed specifically for our clinical study. According to the model function used, the nonlinear-least-squares parametric estimation applied to the lipid spectra can lead to an ill-posed nonlinear problem. We demonstrated that the use of a simplified model based on the structure of a triglyceride chain, as recently used in quantitative imaging, was a valid solution regarding the state of the art. Then different methods (MRI, MRS, Dual Energy X-ray absorptiometry, gas chromatography) were used to characterize the subcutaneous and visceral AT. We demonstrated the feasibility of MRI to follow the lipid content in the liver as well as the volume and the fatty acid composition of AT using a single multiple gradient-echo acquisition. Finally, experimental developments were carried out in parallel with the clinical study, on a 4.7T preclinical system, first, to compare different strategies for encoding the chemical shift using imaging and, secondly, to characterize MRS methods for in vivo estimation of the relative proportion of omega-3 among all fatty acids., L’imagerie et la spectroscopie par résonance magnétique nucléaire (IRM et SRM) sont des méthodes non-invasives qui ont le potentiel d’estimer in vivo la quantité et la qualité des adiposités abdominales. Le contexte scientifique et clinique de ce manuscrit s’articule autour de l’étude de surnutrition « Poly-Nut » dont l’un des objectifs est d’analyser les évolutions des tissus adipeux (TA) dans une phase rapide de prise de poids. L’originalité et la complexité de cette thèse résident dans le développement, l’adaptation et la comparaison de plusieurs méthodes quantitatives d’IRM et de SRM, pour l’étude du signal lipidique dans un contexte clinique à 3T. La fiabilité et la validation des mesures obtenues in vivo par ces techniques font ici l’objet d’une étude approfondie. Pour l’analyse quantitative du signal de spectroscopie, différentes méthodes existantes ont été comparées à celle développée spécifiquement pour notre étude clinique. L’estimation paramétrique par moindres carrés non linéaires appliquée aux spectres RMN des lipides peut conduire, selon la fonction modèle utilisée, à un problème non linéaire mal posé. Nous montrons alors que l’utilisation d’un modèle simplifié se fondant sur la structure d’une chaine de triglycéride, comme utilisé récemment en imagerie quantitative, constitue une solution valide au regard de l’état de l’art. Ensuite différentes méthodes (IRM, SRM, Dual Energy X-ray absorptiometry, chromatographie en phase gazeuse) ont été utilisées pour caractériser les TA sous-cutanés et viscéraux. Le suivi par IRM du contenu lipidique du foie ainsi que du volume et de la composition en acide gras des TA à partir d’une unique acquisition en multi-écho de gradient est démontré. Enfin des développements expérimentaux menés parallèlement à l’étude clinique sur un imageur préclinique à 4,7T, comparent différentes stratégies d’encodage du déplacement chimique par imagerie et caractérisent des méthodes SRM pour estimer in vivo la proportion d’omégas-3 dans les chaînes d’acides gras.

Impaired quality due to a high content of free fatty acids (FFA) and off-flavors has caused challenges in the development of Norwegian goat milk products. The present study aimed to examine the effect of lipid-supplemented concentrates on milk fat content, fatty acid composition, FFA, lipoprotein lipase activity, sensory properties, and size of milk fat globules of goat milk. Thirty goats assigned to 3 experimental groups were fed different concentrates from 60 d in milk (DIM) until late lactation (230 DIM). The diets were (1) control concentrate (no added fat); (2) control concentrate with 8% (added on air-dry basis) hydrogenated palm oil enriched with palmitic acid (POFA); and (3) control concentrate with 8% (added on air-dry basis) rapeseed oil (RSO). The POFA group produced milk with the highest fat content, and fat content was positively correlated with the mean size of milk fat globules. Goats in the RSO group had a higher content of long-chain and unsaturated fatty acids, whereas milk from goats in the POFA group had a higher content of palmitic and palmitoleic acids (C16:0 and C16:1 cis). The control group produced milk with a higher content of short-, medium-, odd-, and branched-chain fatty acids compared with the 2 other groups. The content of FFA in milk was low in early and late lactation and peaked in mid lactation (90 DIM). A high content of FFA was correlated with poor sensory properties (tart/rancid flavor). The RSO group produced milk with lower content of FFA and off-flavors in mid lactation and a higher proportion of unsaturated fatty acids. Therefore, replacement of palm oil with rapeseed oil as a lipid source in dairy goat feed would be favorable.

In Press; The milking of Salers cows requires the presence of the calf. The removal of the calf would simplify the milking routine, but it could also modify the milk yield and the milk and cheese composition. Therefore, the aim of this experiment was to evaluate the effect of calf presence during milking during sampling period (winter or grazing periods), on dairy performance, milk fatty acid (FA) composition, lipolysis and cheese yield and composition. Nine and 8 Salers lactating cows were milked in the presence (CP) or absence (CA) of their calves respectively. During winter, the cows were fed a hay-based diet and then they only grazed a grassland pasture. Calf presence during milking increased milk yield and milk 16:0 concentration and decreased milk fat content and milk total odd- and branched-chain FA (OBCFA) concentrations. Calf presence only increased initial lipolysis in milk collected during the winter season. Milk from CP cows compared to CA cows resulted in a lower cheese yield and ripened cheeses with lower fat content. Milk from the grazing season had lower saturated medium-chain FA and OBCFA concentrations and higher 18:0, cis-9-18:1, trans-11-18:1 and cis-9, trans-11-CLA concentrations than that from the winter season. Initial milk lipolysis was higher in the winter than in the grazing season. These variations could be due to seasonal changes in the basal diet. Furthermore, the effect of calf presence during milking on milk fat composition was lower than that on dairy performance, cheese yield and composition. Removing the calf during the milking of Salers cows seems feasible without a decrease in milked milk, and with a positive effect on cheese yield and fat content, under the condition that we are able to select cows having the capacity to be milked easily without the calf.

The aim of the study was to test the prediction performance of the fatty acid (FA) composition of beef (Rectusabdominis, RA) with a NIRS (near infrared spectroscopy) equipment. In order to have a representative database ofFrench beef FA composition, 364 RA were sampled on carcasses from different rearing systems (dairy or beef ; youngbulls, cows, steers or heifers ; pasture, hay or corn silage with or without extruded linseed concentrates). FAcomposition was assessed using gas chromatography and spectra were measured at wavelengths between 400 and2500nm. The results show that NIRS accurately predicts several individual FA (16:0, 18:1d9cis) and FA groups (totalsaturated, monounsaturated FA) (RPD>2.0). For other FA and especially polyunsaturated fatty acids (PUFA) n-6 or n-3, the performances should still be improved for quantitative purposes.

A meta-analysis on the influence of dietary lipid or fatty acid (FA) contents on beef FA composition was conductedusing the “ω3Meat” database. This database contains bibliographic data posterior to year 2000 related to the impact ofcattle farming system parameters on beef FA composition. The results of the meta-analysis pointed that 1) Theproportion of C18:3 n-3 present in cattle muscle is directly proportional to its percentage in the diet and to the fatcontent of the diet, 2) Diet lipid content seems to be the most important factor of variation of n-6 PUFA and trans FApresent in cattle muscle. Thus, meta-analysis is a useful tool to assess and summarize the knowledge to accuratelypredict FA composition of ruminant meat even in rearing conditions.

Effect of fat composition on the development of bacterial communities in Cantal-type cheeses. IDF Cheese Science and Technology 2016

Regarding beef meat, consumers have specific expectations especially concerning meat quality traits (tenderness and tasteespecially) but also nutritional value of meat (fatty acid composition in particular). Thus, the aim of the present work was todetermine to what extent the choice of animal breed and type will meet the consumer’s expectations.The study concerned 75 young bulls from three different breeds (Blond d’Aquitaine, Limousin, Angus) and 13 Charolaisheifers.Overall, the oxidative metabolism appears associated with higher tenderness but lower nutritional value of meat (lesspolyunsaturated fatty acids, more saturated ones). However, for a given breed / a given type of animal, it is difficult toassociate clearly a kind of fatty acid composition and a level of tenderness, letting us suppose that a trade-off has to beestablished, in order to satisfy the various consumers’ expectations.

Olive oil flavour represents the most important factor that influences customer’s perception for quality. In thisstudy, an innovative aromatisation approach that enhanced quality and shelf life of olive oil is tested by means of in situ ultrasound-assisted extraction of [i]Carum carvi[/i] L. seeds in olive oil. After the flavouring process, carvone and limonene, representing 99 % of caraway essential oil, were identified in virgin olive oil as revealed by headspace solid-phase microextraction gas chromatograph coupled to mass spectrometer (HS-SPME gas chromatograph (GC)/mass spectrometer (MS)) analyses. Furthermore, kinetic studies indicate that flavouring rate in ultrasound-assisted system is faster than conventional aromatisation producing very stable aromatisedoil with no changes in quality. This fact is attributed to ultrasound contribution to mass transfer intensification of essential oil components from seeds to the bulk medium, confirmed by scanning electron micrograph (SEM) micrographs in which cell damage and exudation of its main content are illustrated. However, it is important to note that ultrasound-treated samples produce higher degrees of conjugated dienes and conjugated trienes compared to conventional maceration. Nevertheless, this increase is not alarming and remains within permitted values of the European Community and the International Olive Oil Council (IOOC). Ultrasoundflavouring system stands as a fast alternative aromatisation method, which allows on top shelf life enhancement and olive oil quality preservation.

Beef quality

Terrestrial plant resources are increasingly used as substitutes for fish meal and fish oil in fish feed in order to reduce the reliance of aquaculture on marine fishery resources. Although many studies have been conducted to assess the effects of such nutritional transition, no whole breeding cycles of fish fed diets free from marine resources has been reported to date. We therefore studied the reproductive performance of trout after a complete cycle of breeding while consuming a diet totally devoid of marine ingredients and thus of n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFAs) that play a major role in the formation of ova. Two groups of female rainbow trout were fed from first feeding either a commercial diet (C, marine and plant ingredients), or a 100% plant-based diet (V, blend of plant proteins and vegetable oils). Livers, viscera, carcasses and ova were sampled at spawning and analyzed for lipids and fatty acids. Although the V-diet was devoid of n-3 LC-PUFAs, significant amounts of EPA and DHA were found in livers and ova, demonstrating efficient bioconversion of linolenic acid and selective orientation towards the ova. Some ova were fertilized to assess the reproductive performance and offspring survival. We observed for the first time that trout fed a 100% plant-based diet over a 3-year breeding cycle were able to produce ova and viable alevins, although the ova were smaller. The survival of offspring from V-fed females was lower (-22%) at first spawning, but not at the second. Our study showed that, in addition to being able to grow on a plant-based diet, rainbow trout reared entirely on such a diet can successfully produce ova in which neo-synthesized n-3 LC-PUFAs are accumulated, leading to viable offspring. However, further adjustment of the feed formula is still needed to optimize reproductive performance.

Prédiction de la composition en acides gras des lipides de la viande bovine par spectroscopie proche infrarouge (SPIR). 11. Journées Francophones de Nutrition, JFN 2013

absent

Dans le but de sélectionner de nouveaux produits végétaux ayant des propriétés thérapeutiques, la présente étude porte sur l’évaluation de l’effet hypolipémiant de l’huile d’oléastre, poussant dans la région de Tlemcen. Les indices de qualité (densité relative, indice de réfraction, indice d’acide et indice de saponification) ainsi que le dosage des polyphénols de cette huile étudiée sont conforment aux normes commerciales. La composition en acides gras de l’huile issue des fruits d’oléastre a révélé une richesse en acides gras polyinsaturés (AGPI) notamment les acides gras monoinsaturés (AGMI), l’élément responsable de l’amélioration des lipides sériques. L’expérimentation a été menée sur des rats de souche « Wistar » recevant des régimes riche en cholestérol et sans cholestérol. Nos résultats démontrent que le régime à base de l’huile d’oléastre augmente les taux du cholestérol total et des lipoprotéines de haute densité et diminue celui des lipoprotéines de basse densité comparés au régime à base de l’huile de tournesol, et ce dans les deux régimes. En outre, le cholestérol supplémenté aux régimes provoque une augmentation du taux des lipides totaux du foie, cependant une nette diminution a été observée chez les rats nourris à l’huile d’oléastre par rapport à ceux nourris à l’huile de tournesol. En conclusion, l'étude a révélé que l’oléastre est intéressant, car son huile produite fournit des composés de bonne qualité en termes d’AGMI, d’AGPI et des phénols. En outre, cette huile affecte positivement le profil lipidique au niveau du plasma. Par conséquent, elle peut être utilisée dans la thérapie humaine.