Effects of graded levels of duodenal infusions of leucine on mammary uptake and output in lactating dairy cows
Effects of graded levels of duodenal infusions of leucine on mammary uptake and output in lactating dairy cows
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DOI：
10.1017/s0022029906001841
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发表时间：
2006-08-01
影响因子：
2.1
通讯作者：
Pisulewski, Pawel M.
中科院分区：
文献类型：
--
作者：
Rulquin, Henri;Pisulewski, Pawel M.
选取4头经产荷斯坦奶牛，分别安装十二指肠插管和超声乳腺血流探头，置于4 × 4拉丁方区，测定十二指肠灌注亮氨酸（0、40、80和120g/d）对泌乳反应和乳腺营养物质代谢的影响。饲喂玉米青贮67.0%、干草5.3%、豌豆14.2%、玉米淀粉7.8%、糖蜜、尿素和碳酸氢钠各1.0%、矿物质和维生素2.4%的饲粮。其余9种必需氨基酸的需求通过向十二指肠注入323 g/d的氨基酸混合物来满足，这些氨基酸包括：lie、Val、met、Lys、Trp、Phe、His、Thr、Arg、Tyr和Glu。乳蛋白含量和产量在添加40 g/d亮氨酸时最高，随后逐渐下降。在整个输注亮氨酸的范围内，乳脂含量和产量均显著降低。当添加80 g/d亮氨酸时，亮氨酸的动脉浓度呈线性增加，相应的乳腺动静脉差异趋于平稳，随着亮氨酸输注量的增加，亮氨酸的提取率呈线性下降，而Ile、Val、Lys、Arg、Thr和Tyr的提取率显著增加。亮氨酸按泌乳量被乳腺吸收，分别输入0和40 g/d亮氨酸，然后大量过量。根据蛋白质产量和乳腺吸收量对泌乳率的响应，小肠吸收总氨基酸中亮氨酸的浓度应接近8.9%，乳蛋白的合成才能达到最佳水平。
Four multiparous Holstein cows, each equipped with a duodenal cannula and an ultrasonic mammary blood flow probe, were assigned to a 4x4 Latin square to measure the effects of duodenal infusions of Leu (0, 40, 80 and 120g/d) on lactational responses and mammary metabolism of nutrients. Cows were fed a diet of 67.0% corn silage, 5.3% grass hay, 14.2% peas, 7.8% maize starch, 1.0% each of molasses, urea, and sodium bicarbonate and 2.4% minerals and vitamins. Requirements of the remaining 9 essential amino acids were met by infusing into the duodenum 323 g/d of a mixture of amino acids including, lie, Val, Met, Lys, Trp, Phe, His, Thr, Arg, Tyr and Glu. Milk protein content and yield were highest with 40 g/d of Leu and then progressively declined. Milk fat content and yield were significantly decreased over the entire range of Leu infusions. Arterial concentrations of Leu increased linearly and corresponding mammary arterio-venous differences increased to a plateau with 80 g/d of Leu. As Leu infusions increased, extraction rates of Leu decreased linearly, whereas those of Ile, Val, Lys, Arg, Thr and Tyr were significantly increased. Leu was taken up by the mammary gland according to milk output with 0 and 40 g/d of Leu infused and then largely in excess. Based on responses of protein yield and mammary uptake to milk output ratio, Leu concentration in total amino acids absorbed in the small intestine needs to be close to 8.9% for optimal milk protein synthesis.