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Prolonged Winter Undernutrition and the Interpretation of Urinary Allantoin:Creatinine Ratios in White-tailed Deer

Results


Initially, recent MEIs did not differ between the treated and control deer (H0: equal intercepts, F[1,5] = 3.96, P = 0.103). Subsequently, however, MEI increased in the control deer (F[2,40] = 3.86, P = 0.029), except during 15-19 April (Fig. 1).

Temporal patterns of urinary A:C ratios differed significantly between restricted and control deer (F[2,46] = 9.45, P = 0.001) (Fig. 2), even though initially there was no significant difference (H0: equal intercepts, F[1,5] = 1.40, P = 0.289) (Fig. 2). Urinary A:C ratios of control deer increased slightly throughout the study (H0: β1 = 0, T46 = 1.59, P = 0.119; H0: β2 = 0, T46 = 1.76, P = 0.086), whereas those of restricted deer exhibited a pronounced increase by 7 April (H0: β1 = 0, T46 = 2.59, P = 0.013; H0: β2 = 0, T46 = 3.98, P = 0.001). There was no significant relation between recent MEI and urinary A:C ratio (H0: β1 = 0, T43 = 0.21, r2 = 0.01, P = 0.839) of the seven deer (Fig. 3) but there was a marginally significant curvilinear relation between A:C ratios and progressive percent mass loss (H0: β3 = 0, T41 = 1.63, r2 = 0.42, P = 0.110) (Fig. 4). Short-term severe nutritional restriction (15-19 April) had no apparent or consistent effect on the A:C ratios of the already restricted deer or the control deer (Table 1). The urinary A:C ratio was significantly related to the urinary UN:C (H0: β1 = 0, T49 = 9.50, r2 = 0.59, P < 0.001) and 3-MeH:C ratios (H0: β1 = 0, T49 = 5.65, r2 = 0.43, P < 0.001).

Figure 1 - Plotted Chart (treatment vs. control): Metabolizable energy intake (MEI) over 4 February through 5 May 1988
Fig. 1.  Recent (2 days prior to urine sampling) mean metabolizable energy intake (MEI) of captive adult white-tailed deer (Odocoileus virginianus) fed either restricted (treatment) or ad libitum (control) amounts of a low-protein, low-energy (LPLE) commercial diet from 11 February to 5 May 1988 at Grand Rapids, Minnesota. Prior to the study, all deer were maintained on a high-protein, high-energy commercial diet, but consumption was not monitored prior to initiation of the study. Sample sizes were four and three deer in the treatment and control groups, respectively.

Figure 2 - Plotted Chart (treatment vs. control): Urinary A:C ratio over 4 February through 5 May 1988
Fig. 2.  Urinary allantoin:creatinine ratios of captive adult white-tailed deer maintained on a high-protein, high-energy commercial diet through 10 February 1988 and fed either restricted (treatment) or ad libitum (control) amounts of a low-protein, low-energy (LPLE) commercial diet from 11 February to 5 May 1988 at Grand Rapids, Minnesota. Sample sizes were four and three deer in the treatment and control groups, respectively.

Figure 3 - Plotted Chart (treatment vs. control): Urinary A:C ratio over Mean daily MEI
Fig. 3.  Urinary allantoin:creatinine ratios versus recent (2 days prior to urine sampling) mean daily metabolizable energy intake (MEI) of captive adult white-tailed deer fed restricted (treatment) or ad libitum (control) amounts of a low-protein, low-energy (LPLE) commercial diet from 11 February to 5 May 1988 at Grand Rapids, Minnesota. Sample sizes were four and three deer in the treatment and control groups, respectively. The thick vertical line demarcates the winter maintenance requirement of captive white-tailed deer (561 kJ/kg0.75 body mass per day; Ullrey et al. 1970).

Figure 4 - Plotted Chart (treatment vs. control): Urinary A:C ratio over Cumulative mass loss
Fig. 4.  Relationship of urinary allantoin:creatinine ratios to cumulative body-mass loss in captive adult white-tailed deer that consumed varying amounts of a low-protein, low-energy (LPLE) commercial diet from 11 February to 5 May 1988 at Grand Rapids, Minnesota. Sample sizes were four and three deer in the treatment and control groups, respectively.


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