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Branched chain amino acids requirements and metabolism in pigs

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

Dokumenter

  • Elham Assadi Soumeh
There is an interest to reduce the dietary crude protein (CP) level to promote the gut health of piglets, eliminate the environmental nitrogen load from intensive pig farming, and to reduce diet costs. This is possible by estimating individual amino acid (AA) requirements and by optimizing the diet according to the ideal protein profile that is compatible with the animal AA demand for normal body function. During the past decades, it has been tried to understand and characterize branched chain amino acids (BCAA) requirements, biological importance, and mode of actions. This is interesting for two reasons: first, BCAA share the same enzymes in their catabolic pathways, and there is an interaction among them in a way that excess Leu for example increases the catabolism of them all and changes the requirements. Second, BCAA are not only building blocks of protein biosynthesis, but are also involved in important regulatory mechanisms and biological functions, e.g. muscle protein synthesis, chronic diseases, neurotransmitter biosynthesis, and so on. Identifying biomarkers of the BCAA status may help to understand their biological effects. The objectives of the current study were first to estimate Ile, Val, and Leu requirements in ratio to Lys for pigs after weaning and second, to study the metabolic profile in blood and urine of pigs fed with different BCAA in the diet, and finally, to identify the biomarkers of BCAA, when pigs were fed with the optimum dietary BCAA level to support the best growth performance.
Three dose-response studies were carried out to estimate the required standardized ileal digestible (SID) isoleucine (Ile), valine (Val), and Leu in ratio to lysine (Lys) for the highest growth performance as well as to collect blood and urine samples from pigs for further investigation. A non-targeted metabolomics study was thereafter conducted in order to screen the bio-fluids of pigs for discriminating metabolites and identify biomarkers of BCAA, when the pigs were fed the optimum level of BCAA for the highest growth performance. The results of the Ile dose-response study showed that the maximum animal performance was obtained from 0.51 to 0.53 SID Ile:Lys depending on the chosen performance trait and/or statistical model, and 0.52 SID Ile:Lys was concluded as the requirement. The increasing SID Val:Lys increased average daily feed intake (ADFI) and average daily gain (ADG), and the highest growth performance was obtained in pigs fed the 0.78 SID Val:Lys diet; it was not different from the results of pigs fed the 0.70 SID Val:Lys diet. The highest feed efficiency was obtained in pigs fed 0.70 SID Val:Lys, and the Val requirement was therefore defined at 0.70 SID Val:Lys for pigs after weaning. In the Leu study, the ADFI and ADG of pigs increased from 0.70 to 0.90 and remained constant thereafter. Pigs had the highest feed efficiency, when SID Leu:Lys was 0.80. The fitted curvilinear plateau model to animal growth performance traits estimated the minimum Leu requirements at 0.93.
Metabolomics, one of the last “-omics”, is a global analysis and interpretation of metabolome in specific health or nutritional status. Non-targeted metabolomics is used for screening the metabolic profile, and the metabolic signature could be used for hypothesis generation. The results of a non-targeted LC-MS metabolomics approach in the current study provided novel knowledge of the metabolic response of pigs to increasing dietary BCAA and enabled us to identify the biomarkers of BCAA in plasma and urine of pigs when fed the optimum dietary Ile, Val, and Leu for the highest growth performance.
Plasma 3-methyl-2-oxovaleric acid, Tyr, hypoxanthine, Trp, indoxylsulfuric acid, glycocholic acid, tauroursodeoxycholic acid, taurocholic acid, LysoPC and urinary phenylacetylglycine, hippuric acid, itaconic acid, Ile 3-hydroxy-3-methyl-glutaric acid, and 2-methylbutyrylglycine were discriminating the pigs fed the increasing dietary SID Ile:Lys level. The most important discriminating metabolites to increasing SID Val:Lys in the diet were plasma hippuric acid, Trp, arachidonic acid ethyl ester, docosahexaenoic acid ethyl ester and urinary 2-pyrrolidinone, glutamate, creatinine, and acetyl-DL-leucine. The metabolites altered by increasing SID Leu:Lys in the diet were plasma Phe, α-ketoisovaleric acid, creatine, Ile, 3-methyl-oxovaleric acid, Trp and urinary Ile, glutamate, choline, cytosine, 3-hydroxy-2-methyl-[S-(R,R)]-butanoic acid, acetyl-DL-valine, L-2-aminoadipic acid, 2-methylbutyrylglycine, Tyr, and L-ascorbic acid. Among the identified metabolites, those that could be linked to the animal growth performance were plasma glycocholic acid and taurocholic acid which were concluded as biomarkers of the optimum dietary Ile level. Plasma creatine, urinary 2-aminoadipic acid, ascorbic acid, and choline were identified as biomarkers of the optimum dietary Leu level. The optimum dietary Val had a less pronounced metabolic signature in plasma and urine of the pigs. The identified biomarkers are important intermediate metabolites involved in different metabolic pathways. The biomarkers could potentially be used as response criteria in dose-response studies and should be assessed in further details to see if they can replace or complement traditional methods.  
OriginalsprogEngelsk
Antal sider123
StatusUdgivet - 2015

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