Journal of Animal Science, Vol 69, Issue 3 1162-1166, Copyright © 1991 by American Society of Animal Science

JOURNAL ARTICLE

Simplified calculation of the NRC estimates for net energy for maintenance in beef cattle diets

L. B. Bruce and M. L. Herlugson
University of Alaska, Fairbanks.

Calculation of dietary intake for beef cattle using the equation outlined by the NRC (1984) is confounded by the need to know the net energy for maintenance content of the diet (NEmkg). Intake cannot be calculated until NEmkg is specified, but intake must be indicated before performance can be predicted. To calculate NEmkg, dietary intake must be known or estimated, or it can be calculated using a complicated quartic equation. This quartic equation, when solved, gives the percentages of selected feedstuffs necessary to balance a diet. Placing the resulting percentages of feedstuffs necessary back into the generalized net energy equation solves for NEmkg. The quartic equation may be simplified by inserting imaginary nutrient values that optimize the equation for simplicity. It remains a quartic equation, but the coefficients for the first three factors of the equation are fixed, with only the unary X term and the coefficient containing variables. A modified version of Newton's method of approximating roots of equations estimates the percentage of feed necessary and when incorporated into the generalized net energy equation solves for NEmkg. The final reduced form results in simplified equations for NEmkg for each of the classes of beef cattle that are easily solved by the hand-held calculator.