The total N and P intake and animal production dictate the amount of N and P that feedlot cattle excrete. Each individual feeding operation needs to calculate the total N and P fed and the total production (pounds of beef gain) evaluate the status of N and P excretion. With the previously discussed variation that exists across the feeding industry, book values simply are insufficient. One tool that is available for estimating the N and P output of feedlots on an individual basis is a worksheet developed at the University of Nebraska (Koelsch 1999); it is available at the following website: http:// www.ianr.unl.edu/manure/Koelsch.html. The worksheet allows users to input the number of animals, daily feed intake, dietary CP (N) and P concentrations, and animal performance. The spreadsheet also allows users to estimate the land requirements for manure application, and more importantly, evaluate the influence of a ration change on the amount of land required for manure application.

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