Characterization and mitigation option of greenhouse gas emissions from lactating Holstein dairy cows in East China.

Background: This study investigated greenhouse gas (GHG) emission characteristics of lactating Holstein dairy cows in East China and provided a basis for formulating GHG emission reduction measures. GreenFeed system was used to measure the amount of methane (CH) and carbon dioxide (CO) emitted by the cows through respiration. Data from a commercial cow farm were used to observe the effects of parity, body weight, milk yield, and milk component yield on CH and CO emissions.

Results: Mean herd responses throughout the study were as follows: 111 cows completed all experimental processes, while 42 cows were rejected because they were sick or had not visited the GreenFeed system 20 times. On average, lactating days of cows was 138 ± 19.04 d, metabolic weight was 136.5 ± 9.5 kg, parity was 2.8 ± 1.0, dry matter intake (DMI) was 23.1 ± 2.6 kg/d, and milk yield was 38.1 ± 6.9 kg/d. The GreenFeed system revealed that CH production (expressed in CO equivalent, CO-eq) was found to be 8304 g/d, [Formula: see text]/DMI was 359 g/kg, [Formula: see text]/energy-corrected milk (ECM) was 229.5 g/kg, total CO production (CH production plus CO production) was 19,201 g/d, total CO/DMI was 831 g/kg, and total CO/ECM was 531 g/kg. The parity and metabolic weight of cows had no significant effect on total CO emissions (P > 0.05). Cows with high milk yield, milk fat yield, milk protein yield, and total milk solids yield produced more total CO (P < 0.05), but their total CO production per kg of ECM was low (P < 0.05). The total CO/ECM of the medium and high milk yield groups was 17% and 27% lower than that of the low milk yield group, respectively.

Conclusions: The parity and body condition had no effect on total CO emissions, while the total CO/ECM was negatively correlated with milk yield, milk fat yield, milk protein yield, and total milk solids yield in lactating Holstein dairy cows. Measurement of total CO emissions of dairy cows in the Chinese production system will help establish regional or national GHG inventories and develop mitigation approaches to dairy production regimes.