Research Information System
ADSA 2026 ANNUAL MEETING, Wisconsin, United States Of America, 21 - 24 June 2026, (Unpublished)
Enteric methane (CH₄) and carbon dioxide (CO₂) are major greenhouse gases (GHGs) in dairy
production, exacerbated by heat stress. This study evaluated the effects of
cooling system, parity, stage of lactation, and calving season on CH₄, CO₂, CH₄/CO₂ ratio, and CH₄ per unit of milk (CH₄/milk) in 44 lactating Holstein cows during
summer, with an average temperature-humidity index (THI) of 79.8
(moderate-to-severe heat stress). Cows were housed in standard free-stall pens
(CONT) or pens equipped with fans and sprinklers (TRT) for heat-stress
mitigation. Statistical analyses were performed using SAS 9.4 (TS1M6) to
determine the effects of cooling system on methane emissions and associated
parameters. Cooling systems reduced
daily CH₄ emissions from 3590 ±
2214 g/day in heat-stressed cows to 2004 ± 2133 g/day and lowered the CH₄/CO₂ ratio by 44% (32.2%
vs. 18.0%). Emission intensity (CH₄/milk) decreased from
119.8 ± 75.1 g/L in heat-stressed cows to 79.2 ± 97.9 g/L under cooling.
Primiparous cows emitted more CH₄ (3572 ± 2586 g/day)
and had higher emission intensity (122.2 ± 89.1 g/L) compared to multiparous
cows. Late-lactation cows showed the highest CH₄ intensity (135.2 ± 89.2 g/L), reflecting lower
productivity. Season of calving influenced emissions, with winter-calving cows
showing higher CH₄ (3323 ± 2401 g/day)
than summer-calving cows (1816 ± 1151 g/day). These findings demonstrate that
cooling interventions under severe summer heat stress not only enhance cow
comfort and productivity but also substantially mitigate enteric CH₄ emissions, supporting both animal welfare and
environmental sustainability. Integrating targeted cooling and management strategies
can help reduce the carbon footprint of dairy systems under future climate
change scenarios.
Keywords:
Enteric
methane emission, cooling system, heat
stress, Holstein, dairy sustainability