Libao-Mercado A J, Yin Y, van Eys J, de Lange C F M
Department of Animal and Poultry Science, University of Guelph, Guelph, ON, N1G 2W1, Canada.
J Anim Sci. 2006 Jun;84(6):1351-61. doi: 10.2527/2006.8461351x.
Use of dietary AA in growing pigs reflects digestion and use of digested AA for various body functions. Before evaluating dietary effects on use of digestible AA intake for body protein deposition, a digestibility study was conducted to investigate true ileal AA digestibility and endogenous ileal AA losses in growing pigs fed graded levels of wheat shorts (WS) or casein (CS; control). A casein-based basal diet (basal) was formulated to contain 0.27 g of standardized ileal digestible (SID) Lys per MJ of DE, to which extra Lys was added from WS (WS2, +0.10 g of SID Lys per MJ of DE; WS3, +0.20 g of SID Lys per MJ of DE) or casein (CS3, +0.20 g of SID Lys per MJ of DE). A fifth diet was formulated to be similar in CP level and source as CS3 but in which 6% pectin, a source of soluble non-starch polysaccharides (NSP), was included at the expense of cornstarch (CS3 + pectin). Five Yorkshire barrows (17.5 +/- 1.5 kg of BW) were fitted with a T-cannula at the distal ileum and randomly assigned to 1 of the 5 experimental diets in a 5 x 5 Latin Square design. Apparent ileal digestibility (AID), true ileal digestibility (TID), and endogenous ileal protein losses (EPL) were determined using the homoarginine method. Diet CS level did not influence (P > or = 0.10) TID of most essential AA or EPL (10.4 g/kg of DM intake). Including pectin in the diet did not influence TID of AA (P > or = 0.10) but increased EPL (15.6 g/kg of DM intake; P > or = 0.01). Inclusion of WS in the diet reduced TID of most essential AA (P < 0.01). The TID values for most essential AA, however, were the same (P > or = 0.10) for both dietary WS levels, except for Lys and Met, which were further reduced at the greatest dietary WS level. Increased EPL (P < 0.01) was only observed for WS3 (16 g/kg of DMI). We concluded that (1) the effects of dietary protein source on AID of AA can be attributed both to reduced TID of AA and increased EPL, (2) the impact of dietary WS level on TID of AA and EPL does not seem to be linear, (3) soluble NSP from pectin or WS exerts a greater effect on EPL than insoluble NSP, and (4) because of the metabolic cost associated with EPL and the impacts of feed composition on microbial fermentation in the gut lumen, the effects of feed ingredients on the use of ileal digestible AA for protein deposition should be investigated further.
生长猪日粮中氨基酸的利用反映了氨基酸的消化以及消化后的氨基酸用于各种身体功能的情况。在评估日粮对可消化氨基酸摄入量用于体蛋白沉积的影响之前，进行了一项消化率研究，以调查饲喂不同水平小麦麸（WS）或酪蛋白（CS；对照）的生长猪的真回肠氨基酸消化率和回肠内源性氨基酸损失。配制了一种以酪蛋白为基础的基础日粮（基础日粮），使其每兆焦消化能含有0.27克标准回肠可消化（SID）赖氨酸，从WS（WS2，每兆焦消化能添加0.10克SID赖氨酸；WS3，每兆焦消化能添加0.20克SID赖氨酸）或酪蛋白（CS3，每兆焦消化能添加0.20克SID赖氨酸）中添加额外的赖氨酸。配制了第五种日粮，其粗蛋白水平和来源与CS3相似，但其中含有6%的果胶（一种可溶性非淀粉多糖（NSP）来源），以玉米淀粉为代价（CS3 + 果胶）。五头约克夏公猪（体重17.5±1.5千克）在回肠末端安装了T形套管，并按照5×5拉丁方设计随机分配到5种实验日粮中的一种。使用高精氨酸法测定表观回肠消化率（AID）、真回肠消化率（TID）和回肠内源性蛋白质损失（EPL）。日粮CS水平对大多数必需氨基酸的TID或EPL（每千克干物质摄入量10.4克）没有影响（P≥0.10）。日粮中添加果胶对氨基酸的TID没有影响（P≥0.10），但增加了EPL（每千克干物质摄入量15.6克；P≥0.01）。日粮中添加WS降低了大多数必需氨基酸的TID（P＜0.01）。然而，除赖氨酸和蛋氨酸外，两种日粮WS水平下大多数必需氨基酸的TID值相同（P≥0.10），在最高日粮WS水平下，赖氨酸和蛋氨酸的TID值进一步降低。仅在WS3组（每千克干物质摄入量16克）观察到EPL增加（P＜0.01）。我们得出结论：（l）日粮蛋白质来源对氨基酸AID的影响既可以归因于氨基酸TID的降低，也可以归因于EPL的增加；（2）日粮WS水平对氨基酸TID和EPL的影响似乎不是线性的；（3）果胶或WS中的可溶性NSP对EPL的影响大于不溶性NSP；（4）由于与EPL相关的代谢成本以及饲料组成对肠腔内微生物发酵的影响，应进一步研究饲料成分对回肠可消化氨基酸用于蛋白质沉积的影响。
