The relationship between N use efficiency (NUE) and feed conversion efficiency (FCE) in fattening Charolais yearling bulls fed either fiber or starch diets.

The dashed line is the overall relationship. Equations for the overall, within-starch and within-fiber relationships are NUE = 1.314×FCE– 0.067 (r² = 0.74; P < 0.01), NUE = 1.450×FCE– 0.091 (r² = 0.73; P < 0.01), and NUE = 0.530×FCE + 0.055 (r² = 0.21; P = 0.13), respectively.