Deep litter removal frequency rate influences on greenhouse gas emissions from barns for beef heifers and from manure stores

• Greenhouse gas emissions were measured in a barn and a manure store in a deep litter system.
• Two manure removal frequency rates from the barn were compared.
• Effects on the gas emission pattern were observed, but not on total greenhouse gas emissions.
• Contribution of the manure to the total greenhouse gas emissions was important.
• Avoiding manure storage during the warm season is recommended.

The emission of greenhouses gases (GHG) from ruminant production systems needs to be reduced. This can be achieved partly by better manure management, particularly for deep litter (DL) systems. Two contrasting removal frequency rates (1×, every 63.5 ± 3.5 days; and 3×, every 23.1 ± 1.5 days) were compared in a DL system for Belgian blue double-muscled heifers, focusing on CO2, CH4 and N2O emissions from the barn and during two manure storage periods, one mainly in autumn and the other mainly in winter. No significant effect (p = 0.447) of manure removal frequency on total GHG emissions was observed (1×: 10.2 ± 3.5; 3×: 8.7 ± 2.2 kg CO2 eq. kg−1 live weight gain).The manure contributed significantly to total GHG emissions (average of 38.9 ± 8.0% of CO2 eq.), emissions from the barn (4.0 ± 0.7%) and manure store included (34.9 ± 8.7%). Higher emissions (time 4.8 in CO2 eq.) from manure were observed when it was stored during the warmer period than the colder one. Large variations in emission pattern with the manure removal frequency rates were also observed, leading potentially (not measured) to higher emissions from the 1× treatment than the 3× treatment for a longer storage period than the one tested in this experiment (63 ± 1 days). Given the experimental choices, the variations in emission pattern observed indicated that mitigation options for GHG emissions from the barn and manure store related to manure removal frequency depend on manure storage duration and that keeping deep litter manure in barns without intermediate storage before spreading should be investigated. These options need to be confirmed through emission measurement during and after manure spreading in order to avoid a trade-off between emission stages. The relevance of such options in terms of agronomical concerns needs to be confirmed.