Table 3 Plasma N-metabolite concentrations and urea pool size of dairy cows with low (LMU) and high milk urea concentration (HMU) fed normal (NP) and low (LP) dietary crude protein level under conditions 97% of ad libitum feeding.

From: Hepatic urea, creatinine and uric acid metabolism in dairy cows with divergent milk urea concentrations

Parameter

NP

LP

P value2

HMU

LMU

P value3

HMU

LMU

P value3

Diet

Group

Diet × Group

Citrulline, μmol/L

85.5 ± 5.7ab

73.6 ± 6.0ab

0.162

84.2 ± 5.3a

68.1 ± 5.3b

0.042

0.546

0.019

0.714

Glycine, μmol/L

332.3 ± 17.4a

273.0 ± 18.6b

0.027

284.2 ± 16.4ab

322.6 ± 16.4ab

0.109

0.964

0.547

< 0.01

Serine, μmol/L

85.2 ± 5.1a

67.4 ± 5.5b

0.024

72.9 ± 4.8ab

79.6 ± 4.8ab

0.331

0.999

0.282

0.022

Asparagine, μmol/L

48.9 ± 4.0

37.1 ± 4.3

0.055

38.6 ± 3.8

43.0 ± 3.8

0.418

0.583

0.363

0.051

Glutamine, μmol/L

335 ± 18.7a

290.4 ± 20.0ab

0.114

280.6 ± 17.7b

286.1 ± 17.7ab

0.827

0.125

0.300

0.187

Arginine, μmol/L

93.6 ± 6.3a

79.7 ± 6.8ab

0.146

75.1 ± 6.0b

78.6 ± 6.0ab

0.678

0.129

0.417

0.176

Tyrosine, μmol/L

44.3 ± 3.9

33.9 ± 4.2

0.054

39.5 ± 3.7

38.5 ± 3.7

0.843

0.920

0.116

0.187

Aspartate, μmol/L

5.48 ± 0.45a

4.39 ± 0.48ab

0.113

4.21 ± 0.43b

4.51 ± 0.43ab

0.620

0.211

0.391

0.133

Alanine, μmol/L

271 ± 15.7

227.8 ± 16.8

0.070

264.4 ± 14.8

262.5 ± 14.8

0.926

0.375

0.158

0.196

Ornithine, μmol/L

40.2 ± 4.2

42.5 ± 4.5

0.717

35.5 ± 4.0

34.3 ± 4.0

0.831

0.137

0.901

0.680

AST1, U/L

72.1 ± 7

63.2 ± 7

0.398

84.8 ± 7

83.0 ± 7

0.856

0.029

0.459

0.622

Allantoine, μmol/L

570.5 ± 30.7

523.4 ± 32.8

0.303

539.9 ± 29

514.5 ± 29

0.540

0.521

0.243

0.723

Creatine, μmol/L

330 ± 14.3ab

286 ± 15.3b

0.045

315.3 ± 13.5ab

335.3 ± 13.5a

0.305

0.233

0.403

0.032

Creatinine, μmol/L

24.8 ± 2.5

22.5 ± 2.7

0.539

26.8 ± 2.4

23.3 ± 2.4

0.315

0.581

0.260

0.821

Uric acid, μmol/L

76.4 ± 3.1

70.4 ± 3.4

0.204

82.1 ± 3.0

73.6 ± 3.0

0.053

0.165

0.028

0.693

Hippuric acid, μmol/L

78.2 ± 6.3

61.0 ± 6.7

0.072

86.0 ± 5.9

72.4 ± 5.9

0.117

0.132

0.020

0.774

Urea, μmol/L

5831 ± 344ab

5100 ± 368ac

0.028

4647 ± 324 cd

3942 ± 324bd

0.365

< 0.01

0.044

0.969

Urea pool, mg/kg BW

156.6 ± 9.3a

129.8 ± 9.3ab

0.052

123.8 ± 8.8b

107.0 ± 9.3ab

0.199

< 0.01

0.025

0.593

  1. Data are given as least square means and standard error (SE).
  2. a–cDifferent superscript letters within one row indicate P < 0.05 (Tukey test).
  3. 1AST, aspartat-aminotransferase.
  4. 2P value from ANOVA analysis.
  5. 3P value from Tukey slice test.
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