Department of Animal Science, University of Nebraska, Lincoln, Nebraska 68583-0908, USA.
J Anim Sci. 2010 Jul;88(7):2393-402. doi: 10.2527/jas.2008-1435. Epub 2010 Mar 26.
Phosphorus is an expensive nutrient to supplement, and excess may lead to manure P challenges. Therefore, minimizing dietary P to meet requirements is important. Two experiments were conducted to determine the P requirement of finishing cattle (Exp. 1) and to evaluate the effects of feeding different P concentrations on the quantity and route of P excretion (Exp. 2). In Exp. 1, 60 heifers (BW = 278 kg +/- 17 kg) were individually fed 1 of 5 dietary P concentrations (0.10, 0.17, 0.24, 0.31, or 0.38% P). Cattle performance, plasma P concentration, bone characteristics, and bone P concentration were used to determine the P requirement. Intake and ADG increased quadratically (P < 0.01) as dietary P increased. Plasma P in heifers receiving the 0.10% treatment was less (P < 0.01) than the other treatments and suggested that these heifers were experiencing a P deficiency. Total ash weight of the phalanx bones increased linearly (P < 0.01) as dietary P increased. In Exp. 2 using a 5 x 5 Latin square design, 5 different diets varying in P concentration (0.12, 0.27, 0.42, 0.30, and 0.36% P) were fed to steers to evaluate route and quantity of P excreted. Steers excreted little (1.78 g/d on average) P in the urine as a percentage of total P excretion. Steers on the 0.12% P diet excreted very little P in urine (0.50 g/d). Excretion of P was less (P < 0.05) for the cattle fed 0.12% P compared with all other treatments. Results from cattle performance, plasma P concentrations, and bone characteristics indicate that the heifers fed 0.10% P were experiencing a deficiency and the P requirement of finishing heifers is between 0.10 and 0.17% P. Dietary P concentrations of 0.10 to 0.17% P resulted in decreased P excretion. Supplementation of mineral P is unnecessary in grain-based feedlot diets because dietary P will greatly exceed the requirements (<0.17%).
磷是一种昂贵的营养物质，需要补充，过量的磷可能会导致粪便磷含量过高。因此，将日粮中的磷含量降到最低以满足需求非常重要。本试验进行了两项研究，以确定育肥牛的磷需要量（试验 1），并评估不同磷浓度对磷排泄量和途径的影响（试验 2）。在试验 1 中，60 头阉牛（BW=278kg±17kg）分别饲喂 5 种不同磷浓度（0.10%、0.17%、0.24%、0.31%和 0.38%）的日粮。用牛的生产性能、血浆磷浓度、骨骼特征和骨磷浓度来确定磷需要量。随着日粮磷水平的增加，采食量和日增重呈二次曲线增加（P<0.01）。接受 0.10%磷处理的阉牛的血浆磷浓度低于（P<0.01）其他处理组，表明这些阉牛存在磷缺乏。随着日粮磷水平的增加，掌骨的总灰分重量呈线性增加（P<0.01）。在试验 2 中，采用 5×5 拉丁方设计，用 5 种不同磷浓度（0.12%、0.27%、0.42%、0.30%和 0.36%）的日粮饲喂阉牛，以评估磷的排泄途径和排泄量。牛从尿液中排出的磷占总磷排泄量的比例很小（平均 1.78g/d）。饲喂 0.12%磷日粮的牛从尿液中排出的磷非常少（0.50g/d）。与其他处理组相比，饲喂 0.12%磷日粮的牛的磷排泄量减少（P<0.05）。牛的生产性能、血浆磷浓度和骨骼特征的结果表明，饲喂 0.10%磷的阉牛存在缺乏，育肥牛的磷需要量在 0.10%至 0.17%之间。日粮磷浓度在 0.10%至 0.17%之间可减少磷的排泄。由于日粮磷含量将大大超过需要量（<0.17%），因此在谷物型肥育牛日粮中不需要补充矿物质磷。
