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

The amino acid composition of tissue protein is affected by the total sulfur amino acid supply in growing pigs

The factorial approach to assess the amino acid (AA) requirements of pigs is based on the assumption that the AA composition of body protein is constant. However, there are indications that this assumption may not be valid because the AA composition of body protein can be affected by the AA supply. The extent to which different tissues are affected by an AA deficiency is unknown. The objective of this study was to investigate the effect of feeding pig diets with a deficient or sufficient total sulfur AA supply (TSAA; Met+Cys) from 6 to 23 weeks of age on tissue composition and meat quality. The deficient diet (TSAA–) provided 24% Met : Lys and 51% TSAA : Lys on a standardized ileal digestible basis, which are 19% and 16% below the recommended requirements, respectively. The sufficient diet (TSAA+) provided 33% Met : Lys and 60% TSAA : Lys. Diets were offered slightly below the ad libitum feed intake capacity of the pigs. Pigs offered diet TSAA– had a lower average daily gain, lower weights of the longissimus dorsi (LM) and rhomboideus muscles (RM), and of selected skin sections (P<0.05). The weight of different sections of the small intestine and the liver was not affected by the diet. The protein content of the LM and RM decreased in pigs offered diet TSAA– (P<0.05), whereas the protein content of other tissues was not affected. The TSAA supply affected the AA composition (g/16 g N) of protein in all tissues, but the Met content was changed only in the liver (P<0.05). Pigs receiving diet TSAA– had a lower Cys content in the RM and in the distal jejunum and ileum (P<0.01). The deficient TSAA supply resulted in a lower carcass weight and higher muscle glycogen stores (P<0.05), but did not affect other meat quality traits. The results of this study indicate that the muscles, jejunum and ileum respond more to a prolonged AA deficiency than the liver. In addition, the observed changes in AA composition of tissue protein question the use of a constant AA profile of retained protein to assess AA requirements

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

Redução do nível de proteína bruta em rações para frangos de corte em ambiente de estresse por calor

Este estudo foi realizado para avaliar os efeitos da redução do nível de proteína bruta (PB) da ração com suplementação de aminoácidos sintéticos sobre o desempenho e o rendimento de carcaça de frangos de corte de 22 a 42 dias de idade mantidos sob estresse por calor. Utilizaram-se 280 frangos de corte machos da linhagem Cobb 500 com peso inicial de 856 ± 7,41 g, distribuídos em delineamentointeiramente casualizado, com cinco níveis de PB (21,6; 20,6; 19,6; 18,6 ou 17,6%), oito repetições e sete aves por unidade experimental. A temperatura no interior da sala foi mantida em 32,2 ± 0,6ºC, com umidade relativa de 66 ± 3,2% e temperatura de globo negro de 33,0 ± 0,7ºC. O índice de temperatura de globo e umidade (ITGU) calculado no período foi de 83 ± 0,9. Não houve efeito dos níveis de PB da ração sobre o ganho de peso, o consumo de ração e a conversão alimentar das aves. A redução dos níveis de PB da ração influenciou os pesos absolutos da carcaça e do peito, que foram maiores no nível de 19,6% de PB em relação ao de 21,6%. Entretanto, não houve efeito da redução dos níveis de PB sobre os pesos absolutos de coxa e de sobrecoxa nem sobre os rendimentos de peito, coxa e sobrecoxa. O nível de proteína bruta da ração, formulada utilizando-se o conceito de proteína ideal, pode ser reduzido de 21,6 até 17,6%, pois essa redução não prejudica as características de desempenho, nem o peso absoluto e o rendimento de cortes nobres de frangos de corte submetidos a estresse por calor.This study was performed to evaluate the effects of reduction of dietary crude protein level with supplementation of industrial amino acids on the performance and carcass yield of broilers between 22 to 42 days of age, under heat stress. It was used 280 Cobb broilers with initial weight of 856 ± 7.41 g, distributed in a complete randomized experimental design, with five crude protein levels (21.6; 20.6; 19.6; 18.6 and 17.6%), eight repetitions and seven broilers per experimental unit. The temperature inside the rooms was kept at 32.2 ± 0.6ºC, the relative humidity at 66 ± 3.2% and black globe temperature at 33.0 ± 0.7°C. The black globe-humidity index calculated for the period was 83 ± 0.9. There was no effect of crude protein levels on weight gain, feed intake and feed conversion of the birds. The reduction of dietary crude protein levels influenced the absolute weight of carcass and breast, and the level of 19.6% proportioned higher carcass and breast weights of the broilers compared to the level of 21.6% of crude protein. However, there was no effect of the reduction of levels of crude protein on absolute values of thigh and drumstick and also on breast, thigh and drumstick yields. The dietary crude protein level, formulated by using the ideal protein concept, can be reduced from 21.6 to 17.6% not negatively affecting the performance, absolute weight and noble cut yield of broilers under heat stress

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