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Similarly, a significant curvilinear relationship was observed between 3-methylhistidine: creatinine and progressive percent mass loss in the seven deer (Fig. 2; H₀: β₀ = 0, T₆ = -0.06, P = 0.951; H₀: β1 = 0, T₄₁ = 1.42, P = 0.162; H₀: β2 = 0, T₄₁ = - 2.53, P = 0.015; H₀: β3 = 0, T₄₁ = 4.29, P = 0.0001; R² = 0.82). The single observation with 32% mass loss (solid triangle, Fig. 2) was excluded from the regression analysis. This deer was near death and was the only animal to experience >29% mass loss during the study. This deer's final 3-methylhistidine:creatinine ratio did not adhere to the general trend of values and may have been reflective of a breakdown of "normal" physiological processes as it approached death. Until more data are available for such extreme mass loss, we think it prudent to limit statistical inference to the range of mass loss values ≤ 29%.

The 3-methylhistidine:creatinine ratios were strongly related (r² = 0.89) to urea nitrogen:creatinine ratios (Fig. 3). Short-term (4 days) acute, severe nutritional restriction had a minimal effect on urinary 3-methylhistidine:creatinine values in control deer, but it had a dramatic effect on the ratios of the treatment deer (Table 1).