W. F. Ma, S. H. Zhang, X. F.Zeng, X. T.Liu, C. Y. Xie, G. J. Zhang and S. Y. Qiao

    本試驗研究了不同標(biāo)準(zhǔn)回腸可消化色氨酸/賴氨酸比率 ( SID Trp/Lys)對飼喂低蛋白日糧（9.6%）并補充合成氨基酸在育肥母豬生長性能和胴體指數(shù)的影響。選用90頭育肥母豬（89.1±5.1kg）進(jìn)行35天的試驗。玉米-麥麩基礎(chǔ)日糧中添加合成色氨酸（0、0.1、0.2、0.4、0.6g/kg），使日糧中SIDTrp/Lys達(dá)到0.12、0.15、0.18、0.21、0.24。每種處理6欄，每欄3頭育肥母豬。試驗結(jié)束時，每欄選取1頭育肥母豬，共計30頭屠宰后評價胴體性狀和肉質(zhì)（體重121kg）。SIDTrp/Lys增加可以提高日增重（線性和二次效應(yīng)，P＜0.05），同時改善G:F（線性和二次效應(yīng)，P＜0.05）。血清尿素氮含量隨比值的增加而降低（線性和二次效應(yīng)，P＜0.05）。處理對背長肌大理石紋和L*light有二次效應(yīng)（P＜0.05）。SIDTrp/Lys的增加還會提高血漿中生長激素的含量（二次效應(yīng)，P＜0.05），同時提高血漿中IGF-1的水平（線性和二次效應(yīng)，P＜0.05）。提高SIDTrp/Lys可以增加背最長肌中鈉依賴中性氨基酸轉(zhuǎn)運載體2（SNAT2）的蛋白質(zhì)豐度（線性和二次效應(yīng)，P＜0.05）。最大化日增重和G:F，最小化血漿尿素氮水平的合適的SID色氨酸:賴氨酸值在折線模型下分別為0.16、0.17和0.16，在二次方程模型下分別為0.20、0.20、0.20。色氨酸可影響飼喂低蛋白日糧的育肥母豬的血漿生長激素、IGF-1，以及背最長肌SNAT2氨基酸轉(zhuǎn)運載體的蛋白質(zhì)豐度。

    This study investigated the effects ofvarious standardized ileal digestible (SID) Trp to Lys ratios on theperformance and carcass characteristics of late finishing gilts receivinglow-CP (9.6%) diets supplemented with crystalline AA. Ninety gilts (89.1 ± 5.1kg) were used in a dose–response study conducted for 35 d. Crystalline Trp (0,0.1, 0.2, 0.4, or 0.6 g/kg) was added to a corn–wheat bran basal diet providingSID Trp to Lys ratios of 0.12, 0.15, 0.18, 0.21, or 0.24. Each diet was fed to6 pens of pigs with 3 gilts per pen. At the end of the experiment, 30 gilts (1 pigper pen) were slaughtered to evaluate carcass traits and meat quality (BW = 121kg). Increasing the SID Trp to Lys ratio increased ADG (linear and quadraticeffect, P < 0.05) and also improved G:F (linear and quadratic effect, P <0.05). Serum urea nitrogen (SUN) decreased as the SID Trp to Lys ratioincreased (linear and quadratic effects, P < 0.05). A quadratic effect of L*light and marbling in the longissimus dorsi was observed as the dietary SID Trpto Lys ratio increased (P < 0.05). Increasing the SID Trp to Lys ratioincreased the level of serum GH (quadratic effect, P < 0.05) and alsoincreased the level of serum IGF-1 (linear and quadratic effect, P < 0.05).Increasing the SID Trp to Lys ratio increased the protein abundance of themuscular AA transporter of sodium-coupled neutral amino acid transporter 2(SNAT2) in the longissimus dorsi muscle (linear and quadratic effect, P <0.05). The optimum SID Trp to Lys ratios to maximize ADG and G:F as well as tominimize SUN levels were 0.16, 0.17, and 0.16 using a linear-breakpoint modeland 0.20, 0.20, and 0.20 using a quadratic model. Tryptophan could influenceserum GH and IGF-1 secretion and protein abundance of the muscular AAtransporter of SNAT2 in the longissimus dorsi muscle in late finishing giltsfed low-protein diets.