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生长猪日粮中亮氨酸过量会降低其生长性能、蛋白质的生物学价值和存留率、以及血清素的合成

发布单位:必赢bwin官网入口

查看次数：7443

时间：2019-10-16

Kyler R Gilbreath，Gayan I Nawaratna，Tryon A Wickersham，M Carey Satterfield，Fuller W Bazer，Guoyao Wu

翻译&校对：上海亘泰实业集团


通过实验验证了饲粮中过量的亮氨酸（Leu）对生长猪支链氨基酸 （BCAA）代谢的影响。试验选用40头生长猪只（初始体重（BW）：30.0±2.7 kg），单独放置在代谢箱中，采用随机的完全区组设计，分配到5个日粮处理组（每组8个重复）；5种日粮均以相同数量的玉米、豆粕、小麦和大麦为基础，分别含有100、150、200、250或300%的猪只所需标准化回肠可消化Leu；记录猪只起始、结束（15d）时的BW和每日采食量。日粮适应5～7d时采集猪只尿液和粪便样品，试验结束时采集猪只血液和组织样本，检测分析血浆尿素氮（N）、血浆和下丘脑血清素、组织BCAA、血清和组织支链α-酮酸，以及BCAA代谢相关的基因mRNA丰度。



结果表明，随着日粮Leu的增加，猪只ADG、ADFI、G：F呈线性下降（P < 0.05）；饲粮中N的保留率有线性下降的趋势（P = 0.082），蛋白质的生物学价值呈线性下降 （P < 0.05）；血浆尿素N呈线性升高（P < 0.05）；血浆中血清素呈现二次方程式关系减少（P < 0.05），以及下丘脑中血清素呈现线性下降（P < 0.05）；肝脏中BCAA浓度呈线性增加（P < 0.001），然而，骨骼肌中的BCAA水平呈线性下降（P < 0.05）；α-酮异戊酸的浓度在肝脏、骨骼肌以及血清中出现下降现象（线性或二次方程式关系，P < 0.001），骨骼肌（P < 0.001）和血清（P < 0.001）中的α-酮基-β-甲基戊酸分别呈线性和二次方程式关系减少；相反地，肝脏、骨骼肌和血清中的α-酮异己酸分别呈现线性、线性和二次方程式关系增加（P < 0.05、P < 0.001和P < 0.001）；骨骼肌中的线粒体BCAA转氨酶和支链α-酮酸E1α单元脱氢酶的表达量也是线性升高了（P < 0.05）

综上所述，日粮中过量的Leu影响了猪只生长性能、N存留率，这可能是因为增加了异亮氨酸（Ile）和缬氨酸（Val）的分解代谢，反而降低了这些氨基酸的可利用性，导致了蛋白质存留率的降低；而且，日粮中超量的Leu也减少了下丘脑血清素的合成。


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.（转自：猪营养国际论坛）
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