Evaluation of the chromium-EDTA complex and creatinine as markers for urinary volume in cattle

Figures & data

Table 1. Chemical composition of the maize silage and concentrate mixtures.

Item^a	Maize silage	Concentrate^b	Concentrate^c
DM, g/kg as fed	272	875	874
OM, g/kg DM	928	976	956
CP, g/kg DM	84.3	265	157
NDFap, g/kg DM	486	108	110

Notes: ^a DM, dry matter; OM, organic matter; CP, crude protein; NDFap, neutral detergent fiber assayed with a heat-stable amylase and corrected for residual ash and protein. ^b 90:10 diet. ^c 50:50 diet.

Table 2. Voluntary intake and total digestibility in heifers fed diets with different forage-to-concentrate ratios.

	Forage-to-concentrate ratio		SEM	P-value
Item	90:10	50:50
Voluntary intake (kg/d)
DM	6.25	7.58	0.369	<0.01
OM	5.85	7.19	0.334	<0.01
CP	0.63	0.94	0.038	<0.01
NDFap	2.86	2.03	0.251	<0.01
DOM	4.43	5.74	0.312	<0.01
Total digestibility (g/g)
OM	0.758	0.794	0.0132	0.06
CP	0.644	0.706	0.0259	0.02
NDFap	0.678	0.578	0.0254	0.01

Notes: DM, dry matter; OM, organic matter; CP, crude protein; NDFap, neutral detergent fiber assayed with a heat-stable amylase and corrected for contaminant ash and protein; DOM, digested organic matter.

Figure 1. Residual and between animals relative standard deviations and intraclass correlation (correlation between measures within animals taken on different collection days) in heifers fed diets with different forage-to-concentrate ratios. (a) – urinary excretion and urinary concentrations of creatinine and chromium; (b) – urinary creatinine excretion and urinary chromium recovery.

Table 3. Total urinary volume and urinary concentrations of creatinine and chromium in heifers fed diets with different forage-to-concentrate ratios according to the collection days.

Diet	Collection days	Urinary volume (L/d)	Urinary concentration
			Creatinine (mg/L)	Chromium (mg/L)
90:10	1	6.18	1346	72.2
	2	6.53	1360	63.6
	3	7.02	1304	63.9
50:50	1	6.43	1368	62.5
	2	7.13	1289	60.9
	3	7.23	1218	54.6
SEM		1.141	260.3	11.00
Overall mean		6.75	1314	62.9
P-value
Diet (D)		0.57	0.74	0.31
Day (Da)		0.14	0.53	0.08
D × Da		0.87	0.79	0.55

Table 4. Pearson correlations between urine volume and urinary creatinine and chromium concentrations in heifers fed diets with different forage-to-concentrate ratios.

Variable	Variable^a
	Creatinine concentration	Chromium concentration
	Pearson correlations
Urinary volume	−0.726	−0.808
Creatinine concentration	–	0.747
	Partial Pearson correlations^b
Urinary volume	−0.649	−0.592
Creatinine concentration	–	0.782

Notes: ^a All correlation values are different from zero (P < 0.01). ^b Correlations were adjusted for the effects of treatments, animals, periods, and collection days.

Table 5. Creatinine excretion and urinary chromium recovery in heifers fed diets with different forage-to-concentrate ratios according to the collection days.

Diet	Collection days	Variable
		Creatinine excretion (mg/kg BW)	Chromium recovery (mg/mg)
90:10	1	16.58	1.40
	2	17.25	1.28
	3	18.71	1.42
50:50	1	19.24	1.38
	2	19.17	1.39
	3	19.21	1.33
SEM		1.724	0.082
Overall mean		18.36	1.37
P-value
Diet (D)		0.07	0.95
Day (Da)		0.64	0.71
D × Da		0.63	0.41

Table 6. Urinary concentrations of creatinine and chromium in heifers fed diets with different forage-to-concentrate ratios according to the time of urine collection (spot samples).

Collection time	Concentrations^a
	Creatinine (mg/L)	Chromium (mg/L)
6h00	887^c	36.1^c
12h00	1223^b	53.9^b
18h00	1448^ab	50.3^bc
24h00	1601^a	72.3^a
SEM	144.1	7.59
Overall mean	1290	53.2
P-value
Diet (D)	0.46	0.73
Time (T)	<0.01	<0.01
D × T	0.59	0.07

Notes: Means within each response variable with different superscripts differ at P < 0.05.

Table 7. Serum and plasma chromium concentrations in heifers fed diets with different forage-to-concentrate ratios according to blood collection times.

Collection times	Concentrations (mg/L)
	Plasma	Serum
6h00	4.7	9.0
12h00	4.6	8.4
18h00	4.1	6.8
24h00	4.7	7.4
SEM	2.91	1.49
Overall Mean	4.5	8.0
P-value
Diet (D)	0.32	0.52
Time (T)	0.99	0.70
D × T	0.48	0.33

Figure 2. Relationship between predicted and observed values of urinary volumes in heifers fed diets with different forage-to-concentrate ratios [the continuous lines represent the equality (Y = X); the dashed lines represent least square straight lines. Data were adjusted for the random effects of animals and experimental periods. For details on the adjusted equations, please see Table 8. (a), creatinine; (b), chromium.

Table 8. Evaluation statistics of the estimated values of urinary volume (L/d) from spot samples in heifers fed diets with different roughage concentrate ratios as a function of the creatinine and chromium markers.

	Marker
Statistic	Creatinine	Chromium
Mean	6.34	7.44
Linear regression
Intercept	0.190 ± 1.348	0.561 ± 1.446
P-value (β0 = 0)	0.91	0.76
Slope	1.035 ± 0.192	0.833 ± 0.162
P-value (β1 = 1)	0.86	0.33
r^2	0.903	0.920
Mean prediction error	−0.41	0.68
MSPE	0.648	0.874
Components of MSPE
Mean bias	0.169 (26.0%)	0.466 (53.3%)
Systematic bias	0.005 (0.8%)	0.130 (14.9%)
Random errors	0.474 (73.2%)	0.278 (31.8%)

Notes: MSPE, mean square of prediction error.

Figure 3. Activity of the α-ketoglutarate dehydrogenase in the liver of heifers fed diets with different forage-to-concentrate ratios in different biopsies during the experiment (1, beginning of the experiment; 2, end of the first experimental period; 3, end of the second experimental period; P = 0.76).