The effect of vitamin C supplementation on plasma concentration and urinary excretion of vitamin C in cattle
The effect of vitamin C supplementation on plasma concentration and urinary excretion of vitamin C in cattle
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DOI：
10.2527/jas.2007-0060
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发表时间：
2007-12-01
影响因子：
3.3
通讯作者：
Yano, H.
中科院分区：
文献类型：
--
作者：
Padilla, L.;Matsui, T.;Yano, H.
我们研究了补充维生素C的奶牛血浆中维生素C的浓度和尿中维生素C的排泄。将5头奶牛（平均BW = 597 kg）分配至5 x 5拉丁方设计，并补充以氢化大豆油包衣的维生素C制剂，每天每kg BW补充0、10、20、40或60 mg维生素C，持续9天。收集血浆和尿液样品用于测量维生素C浓度。尿中维生素C的排泄量以维生素C与肌酐的比值表示。血浆维生素C浓度和尿维生素C排出量随膳食维生素C的增加呈二次曲线增加（P < 0.001），即最低剂量对血浆维生素C浓度和尿维生素C排出量均无影响，但随着维生素C补充剂量的增加，血浆维生素C浓度和尿维生素C排出量均增加（P < 0.05）。这表明，血浆维生素C浓度影响牛的维生素C尿排泄，并且在每天接受20 mg/kg BW维生素C的奶牛中，血浆维生素C浓度超过维生素C的肾阈值。此外，维生素C的尿排泄增加似乎限制了血浆维生素C浓度，以响应维生素C的摄入。维生素C的日排泄量由报告的每日肌酐排泄量值估算，表明每日排泄到尿液中的维生素C量超过供应的维生素C的一半。因此，很大一部分供应的维生素C可能逃脱瘤胃降解，被吸收，但排泄到尿液中。
We investigated the plasma concentration and urinary excretion of vitamin C in cows supplemented with vitamin C. Five cows (mean BW = 597 kg) were allocated to a 5 x 5 Latin square design and supplemented with a vitamin C preparation coated with hydrogenated soybean oil at 0, 10, 20, 40, or 60 mg of vitamin C per kg of BW per day for 9 d. Plasma and urine samples were collected for measuring vitamin C concentration. Urinary excretion of vitamin C was expressed as the ratio of vitamin C to creatinine. Plasma vitamin C concentration and urinary vitamin C excretion increased quadratically as dietary vitamin C increased (P < 0.001); that is, the lowest dose affected neither plasma vitamin C concentration nor urinary vitamin C excretion but the plasma vitamin C concentration and urinary vitamin C excretion increased (P < 0.05) with increasing supplementation of vitamin C at greater doses. This suggests that plasma vitamin C concentration affects urinary excretion of vitamin C in cattle and that plasma vitamin C concentration exceeded the renal threshold for vitamin C in the cows receiving vitamin C at 20 mg/kg of BW per day. Furthermore, increased urinary excretion of vitamin C appears to limit plasma vitamin C concentration in response to vitamin C intake. The daily excretion of vitamin C was estimated by the reported value of daily creatinine excretion, indicating that the daily amount of vitamin C excreted into urine was more than half of supplied vitamin C. Therefore, a large part of supplied vitamin C probably escapes ruminal degradation and is absorbed but excreted into urine.