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. 2022 Oct 20;12:17593. doi: 10.1038/s41598-022-22536-y

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.

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

Data are given as least square means and standard error (SE).

a–cDifferent superscript letters within one row indicate P < 0.05 (Tukey test).

1AST, aspartat-aminotransferase.

2P value from ANOVA analysis.

3P value from Tukey slice test.