無論大腸桿菌攻毒與否，日糧色氨酸的提高都能改善低水平大分子中性氨基酸下斷奶仔豬的增重和采食量

發(fā)布單位:天津瑞孚農(nóng)牧科技集團有限公司

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時間：2020-10-08
日糧色氨酸是五羥色胺的前體物質(zhì)，五羥色胺是應激相關的神經(jīng)遞質(zhì)。在通過血腦屏障時，色氨酸與其它大分子中性氨基酸（酪氨酸、異亮氨酸、亮氨酸、纈氨酸和苯丙氨酸）相互競爭；因此，調(diào)節(jié)血液循環(huán)中大分子中性氨基酸的水平會影響大腦皮層對色氨酸的利用以及五羥色胺的合成。本論文論證如下假設：在斷奶仔豬攻毒大腸桿菌（ETEC；F4）下，提高日糧色氨酸，并降低大分子中性氨基酸可以提高血漿色氨酸利用率，降低應激指標，從而減少生產(chǎn)性能的損失。
試驗選用96頭雄性仔豬（21±3日齡，6.3±0.98kg，大白×長白），單欄飼喂。試驗為4×2雙因子試驗，包括低色高氨組（0.24%SID色氨酸，5.4%SID大分子中性氨基酸）、低色低氨組（0.24%SID色氨酸，4.6%SID大分子中性氨基酸）、高色高氨組（0.34%SID色氨酸，5.4%SID大分子中性氨基酸）、高色低氨組（0.34%SID色氨酸，4.6%SID大分子中性氨基酸），以及有無大腸桿菌攻毒。攻毒組豬只在斷奶后第7、8天口服0.8ml（3.6×109 cfu/ml）的大腸桿菌。
無論大分子中性氨基酸水平高低，無論在攻毒前還是攻毒后，高色氨酸組豬只血漿色氨酸含量以及色氨酸:大分子中性氨基酸顯著提高（P＜0.001）。未攻毒豬只血漿色氨酸含量以及色氨酸:大分子中性氨基酸顯著高于攻毒組豬只（P=0.03和0.004）。仔豬攻毒后血漿皮質(zhì)醇水平顯著提高（P=0.05），改變?nèi)占Z色氨酸和大分子中性氨基酸水平對血漿皮質(zhì)醇濃度無顯著影響（P＞0.05）。攻毒24小時后，高色低氨組血漿五羥色胺水平顯著高于低色低氨組和高色高氨組。相似的是，高色低氨組在三周試驗期的平均日增重更高（P=0.02）。高色低氨組豬只采食量有提高的趨勢（P=0.08）。
試驗結果表明無論是否被攻毒，提高日糧色氨酸、降低大分子中性氨基酸，提高了血液中色氨酸水平，從而提高血漿五羥色胺濃度，改善仔豬斷奶后生長性能。


Increasing dietary tryptophan in conjunction with decreasing other large neutral amino acids increases weight gain and feed intake in weaner pigs regardless of experimental infection with enterotoxigenic Escherichia coli
Dietary tryptophan (Trp) is a precursor for serotonin, a neuromediator involved in stress responses. Tryptophan competes with other large neutral amino acids (LNAA: tyrosine, isoleucine, leucine, valine, and phenylalanine) to cross the blood–brain barrier; therefore, the regulation of circulating LNAA can influence Trp availability in the cortex and serotonin biosynthesis. The hypothesis examined in this study was that increased supplementation of dietary Trp and a reduction in LNAA for weaned pigs experimentally infected with enterotoxigenic Escherichia coli (ETEC; F4) will increase Trp availability in plasma and reduce indices of the stress response, which will translate to reduced production losses. At 21 ± 3 d of age (mean ± SEM), 96 male pigs (Large White × Landrace) weighing 6.3 ± 0.98 kg (mean ± SEM) were individually penned and allocated to a 4 × 2 factorial arrangement of treatments, with respective factors being 1) four dietary standardized ileal digestible (SID) Trp and LNAA contents, being HTrpHLNAA (Low Trp-High LNAA; 0.24% SID Trp: 5.4% SID LNAA), HTrpHLNAA (Low Trp-Low LNAA; 0.24% SID Trp: 4.6% SID LNAA), HTrpHLNAA (High Trp-High LNAA; 0.34% SID Trp: 5.4% SID LNAA), and HTrpHLNAA (High Trp-Low LNAA; 0.34% SID Trp: 4.6% SID LNAA), and 2) without/with ETEC infection. Pigs were orally infected with 0.8 mL (3.6 × 109 CFU/mL) ETEC at days 7 and 8 after weaning. Pigs fed diets high in Trp irrespective of the level of LNAA (HTrpHLNAA and HTrpLLNAA) had higher plasma Trp concentrations (P < 0.001) and a Trp:LNAA ratio (P < 0.001) before infection and 6 d after infection. Following infection, noninfected pigs had higher plasma Trp (P = 0.03) and a Trp:LNAA ratio (P = 0.004) compared with pigs infected with ETEC. Plasma cortisol levels after infection were higher in ETEC-infected pigs (P = 0.05) and altering dietary Trp and LNAA concentrations did not influence (P > 0.05) plasma cortisol. Pigs fed diet HTrpLLNAA had higher serum serotonin levels 24 h after infection (P = 0.02) compared with pigs fed diets LTrpLLNAA and HTrpHLNAA. Similarly, pigs fed diet HTrpLLNAA had a higher (P = 0.02) average daily gain during the 3-wk study. Overall, average daily feed intake tended to be higher in pigs fed an HTrpLLNAA diet compared with the other diets (P = 0.08). These results suggest that the increased supplementation of dietary Trp with reduced LNAA increased circulating Trp levels that, in turn, likely caused higher serum serotonin levels, irrespective of infection with ETEC, and improved aspects of post-weaning performance.

文章來源：豬營養(yǎng)國際論壇
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