Technical note: Nitrogen isotopic fractionation can be used to predict nitrogen-use efficiency in dairy cows fed temperate pasture
Technical note: Nitrogen isotopic fractionation can be used to predict nitrogen-use efficiency in dairy cows fed temperate pasture
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DOI：
10.2527/jas.2012-5378
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发表时间：
2013-12-01
影响因子：
3.3
通讯作者：
Roche, J. R.
中科院分区：
文献类型：
--
作者：
Cheng, L.;Sheahan, A. J.;Roche, J. R.
本研究的目的是调查草饲奶牛中氮同位素分馏 (delta N-15) 和氮利用效率（牛奶氮/氮摄入量；NUE）之间的关系，这些奶牛补充了越来越多的尿素以模拟春季高瘤胃可降解蛋白牧场。 15 头奶牛被随机分配到新砍伐的牧场，每天补充 0、250 或 336 克尿素。分析饲料、牛奶和血浆的 Delta N-15，分析牛奶和血浆的尿素氮浓度，分析血浆的氨浓度。使用方差分析测试治疗效果，并通过线性回归建立变量之间的关系。与其他两种处理相比，尿素补充量最高（336 克尿素/天）时干物质摄入量（P = 0.002）和产奶量（P = 0.002）较低。牛奶增量 N-15 - 饲料增量 N-15 和 NUE 之间存在很强的线性关系：[NUE (%) = 58.9- 10.17 x 牛奶增量 N-15 - 饲料增量 N-15 (%) (r(2) = 0.83, P < 0.001, SE = 1.67)] 以及血浆增量 N-15 - 饲料增量 N-15 和 NUE 之间存在很强的线性关系： [NUE (%) = 52.4 - 8.61 x 血浆 delta N-15 - 进料 delta N-15 (%) (r(2) = 0.85, P < 0.001, SE = 1.56)]。这项研究证实了 delta N-15 可以预测消耗不同瘤胃可降解蛋白水平的奶牛的 NUE。
The objective of this study was to investigate the relationship between nitrogen isotopic fractionation (delta N-15) and nitrogen-use efficiency (milk nitrogen/nitrogen intake; NUE) in pasture-fed dairy cows supplemented with increasing levels of urea to mimic high rumen degradable protein pastures in spring. Fifteen cows were randomly assigned to freshly cut pasture and either supplemented with 0, 250, or 336 g urea/d. Feed, milk, and plasma were analyzed for delta N-15, milk and plasma for urea nitrogen concentration, and plasma for ammonia concentration. Treatment effects were tested using ANOVA and relationships between variables were established by linear regression. Lower dry matter intake (P = 0.002) and milk yield (P = 0.002) occurred with the highest urea supplementation (336 g urea/d) compared with the other two treatments. There was a strong linear relationship between milk delta N-15 - feed delta N-15 and NUE: [NUE (%) = 58.9- 10.17 x milk delta N-15 - feed delta N-15 (%) (r(2) = 0.83, P < 0.001, SE = 1.67)] and between plasma delta N-15 - feed delta N-15 and NUE: [NUE (%) = 52.4 - 8.61 x plasma delta N-15 - feed delta N-15 (%) (r(2) = 0.85, P < 0.001, SE = 1.56)]. This study confirmed the potential use of delta N-15 to predict NUE in cows consuming different levels of rumen degradable protein.