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生長豬日糧中亮氨酸過量會降低其生長性能、蛋白質的生物學價值和存留率、以及血清素的合成
發布單位:天津瑞孚農牧科技集團有限公司
查看次數：10141
時間：2019-10-16Kyler R Gilbreath，Gayan I Nawaratna，Tryon A Wickersham，M Carey Satterfield，Fuller W Bazer，Guoyao Wu
翻譯&校對：上海亙泰實業集團
通過實驗驗證了飼糧中過量的亮氨酸（Leu）對生長豬支鏈氨基酸 （BCAA）代謝的影響。試驗選用40頭生長豬只（初始體重（BW）：30.0±2.7 kg），單獨放置在代謝箱中，采用隨機的完全區組設計，分配到5個日糧處理組（每組8個重復）；5種日糧均以相同數量的玉米、豆粕、小麥和大麥為基礎，分別含有100、150、200、250或300%的豬只所需標準化回腸可消化Leu；記錄豬只起始、結束（15d）時的BW和每日采食量。日糧適應5～7d時采集豬只尿液和糞便樣品，試驗結束時采集豬只血液和組織樣本，檢測分析血漿尿素氮（N）、血漿和下丘腦血清素、組織BCAA、血清和組織支鏈α-酮酸，以及BCAA代謝相關的基因mRNA豐度。
結果表明，隨著日糧Leu的增加，豬只ADG、ADFI、G：F呈線性下降（P < 0.05）；飼糧中N的保留率有線性下降的趨勢（P = 0.082），蛋白質的生物學價值呈線性下降 （P < 0.05）；血漿尿素N呈線性升高（P < 0.05）；血漿中血清素呈現二次方程式關系減少（P < 0.05），以及下丘腦中血清素呈現線性下降（P < 0.05）；肝臟中BCAA濃度呈線性增加（P < 0.001），然而，骨骼肌中的BCAA水平呈線性下降（P < 0.05）；α-酮異戊酸的濃度在肝臟、骨骼肌以及血清中出現下降現象（線性或二次方程式關系，P < 0.001），骨骼肌（P < 0.001）和血清（P < 0.001）中的α-酮基-β-甲基戊酸分別呈線性和二次方程式關系減少；相反地，肝臟、骨骼肌和血清中的α-酮異己酸分別呈現線性、線性和二次方程式關系增加（P < 0.05、P < 0.001和P < 0.001）；骨骼肌中的線粒體BCAA轉氨酶和支鏈α-酮酸E1α單元脫氫酶的表達量也是線性升高了（P < 0.05）
綜上所述，日糧中過量的Leu影響了豬只生長性能、N存留率，這可能是因為增加了異亮氨酸（Ile）和纈氨酸（Val）的分解代謝，反而降低了這些氨基酸的可利用性，導致了蛋白質存留率的降低；而且，日糧中超量的Leu也減少了下丘腦血清素的合成。
Excess dietary leucine in diets for growing pigs reduces growth performance, biological value of protein, protein retention, and serotonin synthesis
An experiment was conducted to test the hypothesis that excess dietary Leu affects metabolism of branched-chain amino acids (BCAA) in growing pigs. Forty barrows (initial body weight [BW]: 30.0 ± 2.7 kg) were housed individually in metabolism crates and allotted to 5 dietary treatments (8 replicates per treatment) in a randomized complete block design. The 5 diets were based on identical quantities of corn, soybean meal, wheat, and barley and designed to contain 100%, 150%, 200%, 250%, or 300% of the requirement for standardized ileal digestible Leu. Initial and final (day 15) BW of pigs were recorded. Daily feed consumption was also recorded. Urine and fecal samples were collected for 5 d following 7 d of adaptation to the diets. At the end of the experiment, blood and tissue samples were collected to analyze plasma urea N (PUN), plasma and hypothalamic serotonin, tissue BCAA, serum and tissue branched-chain α-keto acids, and messenger ribonucleic acid abundance of genes involved in BCAA metabolism. Results indicated that acid detergent fiber, average daily feed intake, and gain-to-feed ratio decreased (linear, P < 0.05) as dietary Leu increased. A trend (linear, P = 0.082) for decreased N retention and decreased (linear, P < 0.05) biological value of dietary protein was also observed, and PUN increased (linear, P < 0.05) as dietary Leu increased. A quadratic reduction (P < 0.05) in plasma serotonin and a linear reduction (P < 0.05) in hypothalamic serotonin were observed with increasing dietary Leu. Concentrations of BCAA in liver increased (linear, P < 0.001), whereas concentrations of BCAA in skeletal muscle decreased (linear, P < 0.05) as dietary Leu increased. Concentration of α-ketoisovalerate was reduced (linear and quadratic, P < 0.001) in liver, skeletal muscle, and serum, and α-keto-β-methylvalerate was reduced (linear, P < 0.001; quadratic, P < 0.001) in skeletal muscle and serum. In contrast, α-keto isocaproate increased (linear, P < 0.05) in liver and skeletal muscle and also in serum (linear and quadratic, P < 0.001) with increasing dietary Leu. Expression of mitochondrial BCAA transaminase and of the E1α subunit of branched-chain α-keto acid dehydrogenase increased (linear, P < 0.05) in skeletal muscle as dietary Leu increased. In conclusion, excess dietary Leu impaired growth performance and nitrogen retention, which is likely a result of increased catabolism of Ile and Val, which in turn reduces availability of these amino acids resulting in reduced protein retention, and excess dietary Leu also reduced hypothalamic serotonin synthesis.（轉自：豬營養國際論壇）
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