Table 3 Milk yield, milk chemical composition and gas emission of dairy cows, by lactation state

 Milk, kg/d

50.43^a

42.35^b

31.31^c

1.789

< 0.0001

 ECM,² kg/d

45.69^a

40.51^a

31.65^b

1.438

< 0.0001

 Fat, g/d

1720^a

1544^a

1232^b

57.10

< 0.001

 Protein, g/d

1483^a

1379^a

1119^b

43.90

< 0.001

 Casein, g/d

1170^a

1089^a

883.5^b

34.97

< 0.001

 Lactose, g/d

2500^a

2084^b

1511^c

91.36

< 0.0001

 Fat, %

3.425

3.665

3.931

0.5543

0.053

 Protein, %

2.943^a

3.271^b

3.580^c

0.0646

< 0.0001

 Casein, %

2.322^a

2.584^b

2.824^c

0.0526

< 0.0001

 Lactose, %

4.958

9.924

4.819

0.0293

0.130

 Dry matter, %

11.97^a

12.48^ab

12.96^b

0.1228

< 0.01

 Urea, mg/L

225.2^a

297.8^b

326.6^b

10.06

< 0.0001

 Somatic cells, 10³/mL

91.5

100.0

126.6

18.61

0.084

 Urea/protein ratio

76.63^a

91.32^b

91.69^b

2.339

0.007

 Methane production, ppm

606.9^a

507.9^b

471.2^b

12.87

< 0.0001

 Methane yield, ppm/kg DMI³

20.40^a

16.87^b

15.84^b

0.441

< 0.0001

 Methane intensity, ppm/kg ECM

13.45^ab

12.47^a

15.44^b

0.457

0.020

CO₂ production, ppm

5611^a

4118^b

4447^ab

251.8

< 0.05