Functional Amino Acids in Pigs and Chickens: Implication for Gut Health

In pigs and broiler chickens, the gastrointestinal tract or gut is subjected to many challenges which alter performance, animal health, welfare and livability. Preventive strategies are needed to mitigate the impacts of these challenges on gut health while reducing the need to use antimicrobials. In the first part of the review, we propose a common definition of gut health for pig and chickens relying on four pillars, which correspond to the main functions of the digestive tract: (i) epithelial barrier and digestion, (ii) immune fitness, (iii) microbiota balance and (iv) oxidative stress homeostasis. For each pillar, we describe the most commonly associated indicators. In the second part of the review, we present the potential of functional amino acid supplementation to preserve and improve gut health in piglets and chickens. We highlight that amino acid supplementation strategies, based on their roles as precursors of energy and functional molecules, as signaling molecules and as microbiota modulators can positively contribute to gut health by supporting or restoring its four intertwined pillars. Additional work is still needed in order to determine the effective dose of supplementation and mode of administration that ensure the full benefits of amino acids. For this purpose, synergy between amino acids, effects of amino acid-derived metabolites and differences in the metabolic fate between free and protein-bound amino acids are research topics that need to be furtherly investigated

Effect of eicosapentaenoic acid, protein and amino acids on protein synthesis and degradation in skeletal muscle of cachectic mice

Atrophy of skeletal muscle reduces both the quality and quantity of life of patients with cancer cachexia. Loss of muscle mass is thought to arise from a reduction in protein synthesis combined with an enhanced rate of protein degradation, and few treatments are available to counteract this process. Eicosapentaenoic acid (EPA) has been shown to attenuate the enhanced protein degradation, but to have no effect on protein synthesis. This study examines the effect of EPA combined with a protein and amino-acid supplementation on protein synthesis and degradation in gastrocnemius muscle of mice bearing the cachexia-inducing MAC16 tumour. Muscles from cachectic mice showed an 80% reduction in protein synthesis and about a 50-fold increase in protein degradation compared with muscles from nontumour-bearing mice of the same age and weight. Treatment with EPA (1 g kg-1) daily reduced protein degradation by 88%, but had no effect on protein synthesis. Combination of EPA with casein (5.35 g kg-1) also had no effect on protein synthesis, but when combined with the amino acids leucine, arginine and methionine there was almost a doubling of protein synthesis. The addition of carbohydrate (10.7 g kg-1) to stimulate insulin release had no additional effect. The combination involving the amino acids produced almost a doubling of the ratio of protein synthesis to protein degradation in gastrocnemius muscle over that of EPA alone. No treatment had a significant effect on tumour growth rate, but the inclusion of amino acids had a more significant effect on weight loss induced by the MAC16 tumour than that of EPA alone. The results suggest that combination therapy of cancer cachexia involving both inhibition of the enhanced protein degradation and stimulation of the reduced protein synthesis may be more effective than either treatment alone. © 2004 Cancer Research UK

The Influence of Coastal Access on Isotope Variation in Icelandic Arctic Foxes

To quantify the ecological effects of predator populations, it is important to evaluate how population-level specializations are dictated by intra- versus inter-individual dietary variation. Coastal habitats contain prey from the terrestrial biome, the marine biome and prey confined to the coastal region. Such habitats have therefore been suggested to better support predator populations compared to habitats without coastal access. We used stable isotope data on a small generalist predator, the arctic fox, to infer dietary strategies between adult and juvenile individuals with and without coastal access on Iceland. Our results suggest that foxes in coastal habitats exhibited a broader isotope niche breadth compared to foxes in inland habitats. This broader niche was related to a greater diversity of individual strategies rather than to a uniform increase in individual niche breadth or by individuals retaining their specialization but increasing their niche differentiation. Juveniles in coastal habitats exhibited a narrower isotope niche breadth compared to both adults and juveniles in inland habitats, and juveniles in inland habitats inhabited a lower proportion of their total isotope niche compared to adults and juveniles from coastal habitats. Juveniles in both habitats exhibited lower intra-individual variation compared to adults. Based on these results, we suggest that foxes in both habitats were highly selective with respect to the resources they used to feed offspring, but that foxes in coastal habitats preferentially utilized marine resources for this purpose. We stress that coastal habitats should be regarded as high priority areas for conservation of generalist predators as they appear to offer a wide variety of dietary options that allow for greater flexibility in dietary strategies

Modifications métaboliques chez le poulet de chair en climat chaud : conséquences nutritionnelles

National audienceIn broiler chickens, chronic heat exposure significantly decreased basal metabolism but increased diet-induced thermogenesis when expressed as a ratio over metabolisable energy intake. The proportion of energy retention as fat was higher and as protein was lower at 32 degrees C than at 22 degrees C. This may result from modifications in glucose utilisation, as suspected by altered insulin secretion and/or lower tissue sensitivity to this hormone. High ambient temperature increased fatness, particularly for subcutaneous fat. The proportion of saturated fatty acids in fat tissues was higher. The increased fatness in hot conditions was not subsequent to an enhanced hepatic lipogenesis. The secretion flux of the lipoproteins VLDL or total triglycerides, which represent the capacities of lipid output from the liver to the other tissues, were not increased. Finally, the peripheralral uptake of plasma triglycerides by the lipoprotein lipase in fat tissues in fat tissues seemed even reduced. In contrast, the mobilisation of lipids may have been lower. The reduction in protein deposition in hot conditions was mainly due to a decrease in muscle protein synthesis. It is possible that heat exposure changes the requirements of amino acids, some of them may thus be limiting factors to protein synthesis. The lower protein synthesis might also originate from a failure in the energy supply to the muscle or from changes in hormonal control. In hot conditions, although lipid supplementation was not efficient, increasing dietary protein content improved growth performance and protein retention. This effect was favourable but relatively low.Chez le poulet de chair, l’exposition chronique à la chaleur réduit significativement le métabolisme basal, mais accroît l’extrachaleur rapportée à l’énergie métabolisable ingérée. La proportion d’énergie retenue sous forme de lipides est plus élevée et celle retenue sous forme de protéines moindre à 32°C comparés à 22°C. Ceci pourrait provenir de modifications de l’utilisation du glucose, en relation avec une altération de la sécrétion d’insuline et de la sensibilité des tissus à cette hormone. La chaleur accroît l’engraissement, particulièrement au niveau sous-cutané. La proportion d’acides gras saturés dans les tissus adipeux est alors plus élevée. Le fort engraissement au chaud ne paraît pas s’expliquer par une lipogenèse hépatique accrue. Les flux de sécrétion de lipoprotéines de type VLDL ou de triglycérides totaux, qui représentent les capacités d’exportation des lipides du foie vers les autres tissus, ne sont pas non plus augmentés. Enfin, la captation périphérique des triglycérides circulants par la lipoprotéine lipase dans les tissus adipeux apparaît même réduite. En revanche, l’utilisation des acides gras déposés serait plus faible. La réduction du dépôt protéique au chaud provient essentiellement d’une baisse de la synthèse des protéines musculaires. Il est possible que la chaleur modifie les besoins en acides aminés, certains d’entre eux deviendraient alors limitants pour la synthèse protéique. La protéosynthèse pourrait aussi être limitée par un apport énergétique insuffisant au muscle ou en raison de modifications du contexte hormonal. En ambiance chaude, si une supplémentation lipidique n’a que peu d’effet, augmenter le taux protéique de l’aliment améliore les performances et la rétention protéique des animaux. Cet effet, bien que bénéfique, reste pourtant relativement modéré

Effects of age and divergent selection for body weight on muscle protein turnover in chickens

International audienc

Manipulating tissue metabolism by amino acids

Protein metabolism is considered to be regulated by amino acids, with major consequences on tissue development. There is evidence that lysine greatly affects carcass composition and muscle growth. In particular, a drastic effect of dietary provision of lysine has been observed on breast muscle development in chickens. Other essential amino acids, such as threonine and valine, do not have as pronounced an effect as lysine on body composition. Increasing lysine can also improve chicken breast muscle quality by increasing its ultimate pH and water holding capacity, but the underlying mechanisms are still unknown. Studies conducted over the last ten years indicate that, in addition to being substrates for protein synthesis, amino acids act as modulators of signal transduction pathways that control metabolism and cell functions. For instance, certain amino acids can modulate the activity of the intracellular protein kinases involved in the control of mRNA translation. Interestingly, enhanced responses to amino acids have been reported during the neonatal period, suggesting that early protein nutrition impacts on the development of broiler chicks. Methionine and cysteine have a very significant place among amino acids because they have several additional roles: they are precursors of essential molecules, for example cysteine is used for the synthesis of the antioxidant glutathione, and thus participates in the control of oxidative status, methionine is a source of the methyl groups needed for all biological methylation reactions, including methylation of DNA and histones, etc. These findings together indicate the importance of optimizing amino acid nutrition and providing a rationale for nutritional advice. © Copyright World's Poultry Science Association 2011