低蛋白日糧對生長豬氨基酸轉運載體的表達、血清氨基酸濃度、生長性能和胴體組...

畜牧編輯

　　2015. J. Anim. Sci. 93:2154-2164

　　低蛋白日糧對生長豬氨基酸轉運載體的表達、血清氨基酸濃度、生長性能和胴體組成的影響
　　A. Morales, L. Buenabad, G. Castillo, N.Arce, B. A. Araiza, J. K. Htoo and M. Cervantes

　　通常來說，在飼喂蛋白質日糧情形下，豬只空腸中氨基酸轉運載體的表達比十二指腸更高。但是有關晶體氨基酸（其可以在十二指腸被立即吸收）對十二指腸上皮細胞氨基酸轉運載體的表達和生長性能影響的研究還比較少。本試驗將48頭豬只（初始重24.3kg）分為4組，研究日糧粗蛋白水平和形式（氨基酸或蛋白）對各部分小腸氨基酸載體表達、血清氨基酸水平、生長性能的影響。試驗日糧為小麥豆粕型日糧，處理包括1）低蛋白日糧（14%CP），添加賴氨酸、蘇氨酸、蛋氨酸、亮氨酸、異亮氨酸、纈氨酸、組氨酸、色氨酸和苯丙氨酸（LPAA）；2）基礎配方同LPAA日糧，但是僅添加甘氨酸作為氮源（LPAA+N）；3）中蛋白日糧(16%CP)，添加賴氨酸、蘇氨酸、蛋氨酸（MPAA）；4）高蛋白日糧（22%CP，HP），無氨基酸添加。試驗結束時，LPAA和HP組選擇8頭豬只，取小腸黏膜、血清樣品，并解剖胴體。試驗結果表明處理對ADG、ADFI、G:F、胴體組成和內臟器官沒有顯著影響。HP組豬只大腸和腎臟重量較高（P＜0.01）。與HP日糧組相比，LPAA十二指腸b0,+的表達較高（P=0.036），但是空腸和回腸無差異。飼喂LPAA日糧組豬只回腸中y+ L的表達有提高的趨勢（P=0.098）。LPAA組豬只十二指腸和空腸中b0,+的表達無顯著差異，但是在HP組空腸中所有氨基酸載體的表達量均高于十二指腸和回腸（P＜0.05）。HP組豬只血清中精氨酸、組氨酸、異亮氨酸、亮氨酸、苯丙氨酸和纈氨酸濃度較高，但是賴氨酸和蛋氨酸含量較低（P＜0.05）。這些試驗數據表明LPAA最高可以替代高蛋白小麥-豆粕型日糧8個百分點的蛋白而不會影響豬只生長性能。并且，日糧中添加合成氨基酸會影響血清中氨基酸的濃度，以及十二指腸中氨基酸轉運載體b0,+的表達。

　　Low-protein amino acid–supplemented diets for growing pigs: Effect on expression of amino acid transporters, serum concentration, performance, and carcass composition

　　A. Morales, L. Buenabad, G. Castillo, N. Arce, B. A. Araiza, J. K. Htoo and M. Cervantes

　　Pigs fed protein-bound AA appear to have a higher abundance of AA transporters for their absorption in the jejunum compared with the duodenum. However, there is limited data about the effect of dietary free AA, readily available in the duodenum, on the duodenal abundance of AA transporters and its impact on pig performance. Forty-eight pigs (24.3 kg initial BW) distributed in 4 treatments were used to evaluate the effect of the CP level and form (free vs. protein bound) in which AA are added to diets on the expression of AA transporters in the 3 small intestine segments, serum concentration of AA, and performance. Dietary treatments based on wheat and soybean meal (SBM) were 1) low-CP (14%) diet supplemented with l-Lys, l-Thr, dl-Met, l-Leu, l-Ile, l-Val, l-His, l-Trp, and l-Phe (LPAA); 2) as in the LPAA but with added l-Gly as a N source (LPAA+N); 3) intermediate CP content (16%) supplemented with l-Lys HCl, l-Thr, and dl-Met (MPAA); and 4) high-CP (22%) diet (HP) without free AA. At the end of the experiment, 8 pigs from LPAA and HP were sacrificed to collect intestinal mucosa and blood samples and to dissect the carcasses. There were no differences in ADG, ADFI, G:F, and weights of carcass components and some visceral organs between treatments. Weights of the large intestine and kidney were higher in HP pigs (P < 0.01). Expression of b0,+ in the duodenum was higher in pigs fed the LPAA compared with the HP diet (P = 0.036) but there was no difference in the jejunum and ileum. In the ileum, y+ L expression tended to be higher in pigs fed the LPAA diet (P = 0.098). Expression of b0,+ in LPAA pigs did not differ between the duodenum and the jejunum, but in HP pigs, the expression of all AA transporters was higher in the jejunum than in the duodenum or ileum (P < 0.05). The serum concentration of Arg, His, Ile, Leu, Phe, and Val was higher but serum Lys and Met were lower in pigs fed the HP diet (P < 0.05). These results indicate that LPAA can substitute up to 8 percentage units of protein in HP wheat–SBM diets without affecting pig performance; nonessential N does not seem to be limiting in very low-protein wheat–SBM diets for growing pigs. Also, the inclusion of free AA in the diet appears to affect their serum concentration and the expression of the AA transporter b0,+ in the duodenum of pigs.

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