Table 2 Fold change and ANOVA fixed effects statistics of plasma metabolites determined by metabolomics and differing between genetic strains (GS; North American Holstein, NAH, n = 8; New Zealand, NZH, n = 8), days in milk (DIM; 21 vs. 180 DIM) or due to the interaction between genetic strains and days in milk.

\(\alpha \)-keto acids and derivatives

Pyruvic acid

1.37

0.72

0.50

0.79

0.05

0.10

0.58

0.79

AA

Isoleucine

0.85

0.83

0.01

0.27

0.01

0.04

0.01

0.29

AA

Leucine

0.88

0.78

0.01

0.27

0.01

0.03

0.03

0.30

AA

Valine

0.88

0.77

0.02

0.33

0.01

0.02

0.00

0.21

AA

Glutamic acid

0.81

0.83

0.07

0.58

0.03

0.08

0.09

0.34

AA

Aspartic acid

0.95

0.70

0.09

0.58

< 0.01

< 0.01

0.16

0.46

AA

Asparagine

0.94

0.85

0.22

0.62

0.04

0.08

0.58

0.79

AA

Phenylalanine

1.01

0.76

0.24

0.62

< 0.01

< 0.01

0.37

0.66

AA

Glutamine

0.85

0.78

0.24

0.62

0.02

0.06

0.24

0.58

AA

Lysine

0.92

0.70

0.24

0.62

< 0.01

0.01

0.96

0.98

AA

Threonine

0.99

0.74

0.29

0.62

0.01

0.03

0.06

0.33

AA

Tyrosine

0.97

0.72

0.40

0.74

< 0.01

0.02

0.69

0.87

AA

Cysteine

1.02

0.63

0.58

0.85

< 0.01

< 0.01

0.19

0.51

AA

Methionine

1.02

0.77

0.60

0.85

0.01

0.03

0.38

0.66

AA

Histidine

1.05

0.72

0.73

0.92

< 0.01

< 0.01

0.81

0.92

AA

Glycine

1.09

1.35

0.87

0.98

0.04

0.09

0.18

0.50

AA

Alanine

1.06

0.98

0.91

0.98

0.50

0.66

< 0.01

0.02

AA

Tryptophan

1.08

0.70

0.93

0.98

< 0.01

< 0.01

0.78

0.91

AA related

Oxoproline

0.89

0.94

< 0.01

0.22

0.04

0.09

0.43

0.70

AA related

Pipecolinic acid

0.64

0.70

0.01

0.27

0.04

0.09

0.11

0.38

AA related

Homocystine

0.94

1.03

0.03

0.49

0.97

0.98

0.46

0.72

AA related

5-Hydroxynorvaline

0.90

0.81

0.04

0.51

< 0.01

0.01

0.75

0.90

AA related

\(\alpha \)-aminoadipic acid

0.92

0.70

0.05

0.51

< 0.01

< 0.01

0.03

0.30

AA related

N-acetylglycine

0.82

2.15

0.06

0.58

< 0.01

< 0.01

0.36

0.66

AA related

2-Ketoisocaproic acid

0.85

1.05

0.08

0.58

0.92

0.97

0.08

0.33

AA related

Creatinine

1.01

1.01

0.09

0.58

0.38

0.54

0.03

0.30

AA related

3-Hydroxy-3-methylglutaric acid

0.86

0.78

0.10

0.58

0.07

0.14

0.12

0.38

AA related

Ornithine

0.94

0.57

0.14

0.58

< 0.01

0.00

0.54

0.78

AA related

Citrulline

0.96

0.83

0.14

0.58

0.01

0.03

0.55

0.78

AA related

3-Aminoisobutyric acid

0.62

2.23

0.15

0.58

< 0.01

0.01

0.01

0.24

AA related

Phenaceturic acid

0.95

0.75

0.15

0.58

< 0.01

0.02

0.50

0.76

AA related

Kynurenine

1.30

0.55

0.19

0.58

< 0.01

< 0.01

0.50

0.76

AA related

Guanidinosuccinate

1.19

0.73

0.27

0.62

0.00

0.01

0.35

0.66

AA related

Allantoic acid

1.18

1.25

0.31

0.64

0.02

0.04

0.11

0.36

AA related

Cystine

1.19

0.64

0.37

0.71

< 0.01

< 0.01

0.45

0.72

AA related

5-Aminovaleric acid

0.99

1.42

0.40

0.74

0.04

0.10

0.04

0.30

AA related

Aminomalonate

1.06

1.30

0.57

0.85

0.04

0.09

0.21

0.55

AA related

3-(4-Hydroxyphenyl)propionic acid

1.10

0.82

0.73

0.92

< 0.01

0.02

0.35

0.66

AA related

Trans-4-hydroxyproline

1.11

1.46

0.91

0.98

< 0.01

0.01

0.35

0.66

AA related

Phenylacetic acid

1.09

0.76

0.94

0.98

< 0.01

0.01

0.28

0.60

AA related

Cystathionine

1.08

0.89

0.96

0.98

0.01

0.02

0.10

0.35

Bile acids

Cholic acid

1.20

3.00

0.31

0.64

< 0.01

0.01

0.04

0.31

Bile acids

Deoxycholic acid

1.17

2.69

0.34

0.67

0.01

0.02

0.07

0.33

Biogenic amines

Phenylethylamine

1.68

0.23

0.25

0.62

< 0.01

< 0.01

0.01

0.24

Carbohydrates and related

Xylose

0.92

1.20

0.00

0.22

0.16

0.28

0.94

0.97

Carbohydrates and related

Erythritol

1.21

1.06

0.01

0.22

0.90

0.97

0.30

0.62

Carbohydrates and related

1,5-Anhydroglucitol

0.89

1.59

0.06

0.58

0.02

0.04

0.32

0.65

Carbohydrates and related

Xylulose

0.73

1.33

0.08

0.58

0.17

0.30

0.42

0.70

Carbohydrates and related

Mannose

1.03

0.86

0.23

0.62

< 0.01

0.01

0.26

0.59

Carbohydrates and related

Glycerol-\(\alpha \)-phosphate

1.39

0.66

0.28

0.62

0.01

0.04

0.04

0.31

Carbohydrates and related

\(\alpha \)-ketoglutarate

0.91

0.55

0.30

0.63

< 0.01

0.01

1.00

1.00

Carbohydrates and related

Gluconic acid

0.91

0.64

0.63

0.87

0.01

0.03

0.72

0.88

Carbohydrates and related

Glucose

1.13

0.89

0.73

0.92

0.01

0.02

0.22

0.55

Carbohydrates and related

Galactonic acid

0.98

0.59

0.75

0.92

0.01

0.03

0.54

0.78

Carboxylic acids

Isocitric acid

0.93

1.23

0.11

0.58

0.06

0.12

0.16

0.48

Carboxylic acids

Aconitic acid

0.95

1.35

0.15

0.58

0.01

0.04

0.49

0.76

Carboxylic acids

Citric acid

0.94

1.29

0.16

0.58

0.02

0.04

0.05

0.33

Carboxylic acids

Salicylic acid

1.08

0.73

0.96

0.98

< 0.01

0.01

0.63

0.84

Cresols and related compounds

p-tolyl glucuronide

0.61

0.59

0.05

0.51

< 0.01

< 0.01

0.00

0.21

Cresols and related compounds

p-cresol

0.93

0.56

0.19

0.58

0.00

0.01

0.33

0.65

Fatty acids

Arachidic acid

0.96

1.02

0.00

0.22

0.71

0.82

0.08

0.33

Fatty acids

Stearic acid

0.99

1.30

0.04

0.51

0.03

0.07

0.05

0.33

Fatty acids

Nonadecanoic acid

1.04

1.49

0.14

0.58

0.02

0.04

0.08

0.33

Fatty acids

Linoleic acid

0.98

1.44

0.14

0.58

0.01

0.03

0.12

0.38

Fatty acids

Myristic acid

1.05

2.01

0.41

0.74

< 0.01

0.01

0.06

0.33

Fatty acids

Heptadecanoic acid

1.08

1.95

0.44

0.75

< 0.01

0.01

0.07

0.33

Fatty acids

Palmitic acid

1.05

1.40

0.47

0.76

< 0.01

0.02

0.07

0.33

Fatty acids

Arachidonic acid

1.07

1.73

0.65

0.87

< 0.01

0.02

0.22

0.55

Fatty acids

Isolinoleic acid

1.13

0.77

0.78

0.93

0.04

0.09

0.98

0.99

Fatty acids

Palmitoleic acid

1.23

3.99

0.85

0.97

< 0.01

< 0.01

0.06

0.33

Fatty acids

9-Myristoleate

1.07

1.61

0.87

0.98

0.01

0.03

0.03

0.30

Fatty acids

Cerotinic acid

1.04

0.69

0.98

1.00

0.01

0.03

0.29

0.61

Glycerides

1-Monopalmitin

1.18

0.75

0.25

0.62

< 0.01

< 0.01

0.26

0.58

Glycerides

1-Monostearin

1.08

0.73

0.96

0.98

< 0.01

< 0.01

0.37

0.66

Hydroxy acids and derivatives

2-Hydroxyglutaric acid

0.95

1.45

0.32

0.66

< 0.01

0.01

0.54

0.78

Hydroxy acids and derivatives

2-Hydroxybutanoic acid

0.94

1.89

0.45

0.75

< 0.01

0.02

0.28

0.60

Hydroxy acids and derivatives

4-Hydroxybutyric acid

1.05

1.40

0.70

0.92

< 0.01

0.02

0.85

0.96

Imides

Maleimide

1.27

0.81

0.17

0.58

0.04

0.09

0.09

0.34

Indoles and derivatives

Indole-3-propionic acid

1.57

0.86

0.09

0.58

0.02

0.06

0.74

0.90

Indoles and derivatives

Indoxyl sulfate

1.05

0.59

0.88

0.98

< 0.01

< 0.01

0.93

0.97

Inorganic compounds

Phosphate

1.17

0.85

0.43

0.75

0.01

0.03

0.01

0.29

Keto-acids

2-Ketobutyric acid

1.00

0.70

0.59

0.85

0.02

0.04

0.21

0.55

Nitrogenous bases and related

Uric acid

0.77

1.58

0.01

0.28

0.01

0.02

0.38

0.66

Nucleoside and nucleotide analogues

Pseudo uridine

1.10

1.69

0.94

0.98

< 0.01

0.01

0.44

0.70

Phenol esters

4-Hydroxyphenylacetic acid

1.34

1.79

0.17

0.58

< 0.01

0.01

0.53

0.78

Quinolones and derivatives

2,8-Dihydroxyquinoline

0.97

1.47

0.26

0.62

< 0.01

0.01

0.57

0.79

Sterols

Cholesterol

1.31

0.89

0.05

0.51

0.09

0.17

0.88

0.97

Sugar alcohol

Xylitol

0.95

1.32

0.07

0.58

0.02

0.06

0.14

0.42

Sugar alcohol

Isothreitol

1.06

1.32

0.49

0.79

< 0.01

< 0.01

0.64

0.85

Sugar alcohol

Glycerol

1.06

1.54

0.60

0.85

< 0.01

0.02

0.39

0.66

Terpenoids and derivatives

Phytanic acid

1.14

0.70

0.44

0.75

< 0.01

0.02

0.59

0.80

Vitamins and cofactors

\(\alpha \)-tocopherol

1.36

0.75

0.03

0.49

0.01

0.04

0.24

0.58