Effects of dietary crude protein and supplemental urea levels on nitrogen and phosphorus utilization by feedlot cattle
Effects of dietary crude protein and supplemental urea levels on nitrogen and phosphorus utilization by feedlot cattle
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DOI：
10.2527/jas.2008-1411
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发表时间：
2009-03-01
影响因子：
3.3
通讯作者：
Greene, L. W.
中科院分区：
文献类型：
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作者：
Vasconcelos, J. T.;Cole, N. A.;Greene, L. W.
采用完全随机区组设计试验，在2个地点对3个日粮CP浓度（DM的11.5%、13.0%和14.5%）和3个尿素补充水平（N的100%、50%和0%）进行测定，以确定饲养场牛的N、P平衡和血清尿素N（SUN）浓度。杂交牛[英国和英国x大陆;初始BW = 315.0 +/- 3.2 kg（地点1）（n = 27）和初始BW = 353.2 +/- 8.4 kg（地点2）（n = 27）]在开始、中间和饲喂期结束（地点1为154 d，地点2为159 d）。粪氮（g/d; P = 0.03）、尿氮（g/d; P < 0.01）、尿尿素氮（UUN; g/d; P < 0.01）、氮表观吸收量（g/d; P < 0.01）和尿素氮浓度（mg/dL; P < 0.01）随日粮CP浓度的增加而线性增加。氮存留率（g/d）不受日粮CP浓度的影响（P = 0.61）。磷摄入量（g/d; P = 0.02）、粪磷（g/d; P = 0.04）和尿磷（g/d; P = 0.01）随日粮CP增加而线性增加，反映了日粮组成随CP浓度增加而变化。随着日粮尿素水平的增加，尿N（g/d; P = 0.04）、UUN（g/d; P = 0.01）和表观N吸收（g/d; P = 0.04）呈线性增加，而P摄入量（g/d; P = 0.10）和尿P（g/d; P = 0.02）呈线性下降。大多数变量没有观察到SP和饮食治疗之间的相互作用。然而，对SP平均值的评估表明，随着饲喂天数的增加，粪便N（g/d; P = 0.01），尿N（g/d; P < 0.01），UUN（g/d; P < 0.01），氮表观吸收量随着饲喂天数的增加，尿素氮（mg/dL; P <0.01）、尿磷（g/d; P <0.01）呈线性增加，而残留氮（g/d）呈线性下降（P < 0.01）。这些数据表明，日粮CP和尿素水平的变化，以及阶段的饲养期，显着改变饲养场牛的N和P的利用。
Three dietary CP concentrations (11.5, 13.0, and 14.5% of DM) and 3 supplemental urea levels (100, 50, and 0% of supplemental N) were used in a completely randomized block design experiment conducted at 2 locations to determine N and P balance and serum urea N (SUN) concentrations of feedlot cattle. Crossbred steers [British and British x Continental; initial BW = 315.0 +/- 3.2 kg at location 1 (n = 27) and initial BW = 353.2 +/- 8.4 kg at location 2 (n = 27)] were used in 3 nutrient balance sampling periods (SP) at the beginning, middle, and end of the feeding period (154 d in location 1 and 159 d in location 2). Fecal N (g/d; P = 0.03), urinary N (g/d; P < 0.01), urinary urea N (UUN; g/d; P < 0.01), apparent N absorption (g/d; P < 0.01), and SUN concentration (mg/dL; P < 0.01) increased linearly as dietary CP concentration increased. Nitrogen retention (g/d) was not affected (P = 0.61) by dietary CP concentration. Phosphorus intake (g/d; P = 0.02), fecal P (g/d; P = 0.04), and urinary P (g/d; P = 0.01) increased linearly as dietary CP increased, reflecting changes in diet composition with increasing CP concentrations. As dietary urea levels increased, urinary N (g/d; P = 0.04), UUN (g/d; P = 0.01), and apparent N absorption (g/d; P = 0.04) increased linearly, but P intake (g/d; P = 0.10) and urinary P (g/d; P = 0.02) decreased linearly. No interactions were observed between SP and dietary treatments for most variables. Evaluation of SP means, however, showed that as days on feed increased, fecal N (g/d; P = 0.01), urinary N (g/d; P < 0.01), UUN (g/d; P < 0.01), apparent absorption of N (g/d; P < 0.01), SUN (mg/dL; P < 0.01), and urinary P (g/d; P < 0.01) increased linearly, whereas retained N (g/d) decreased linearly (P < 0.01) with increasing days on feed. These data suggest that changes in dietary CP and urea levels, as well as stage of the feeding period, markedly alter N and P utilization by feedlot cattle.