Greenhouse Gases Emissions from Multi-Species Animal Operations and Potential Diet Effects

Abstract. Gas emissions from various animal species were measured in controlled environmental rooms at Michigan State University under various dietary strategies over the course of 17 studies, including two broiler studies, four laying hen studies, one turkey study, two swine studies, four steer studies, two heifer studies, and two dairy cow studies. The objective of this article is to summarize the greenhouse gas (GHG) emission data (CH₄, N₂O, and CO₂) from these 17 studies and the potential diet effects on GHG emissions from multi-species animal operations. The CH₄ concentrations measured by an INNOVA 1412 analyzer showed large discrepancies compared with those measured by a Thermo Scientific Model 55C CH₄ analyzer when CH₄ concentrations were lower than 10 ppm, indicating significant influence of air moisture on the INNOVA measurements of CH₄ at low concentration levels. The ratios of mean measured CH₄ emission rates over estimated values using the Intergovernmental Panel on Climate Change (IPCC) approaches ranged from 25% to 116% in the 17 studies. The measured N₂O emission rates were much higher than the IPCC estimated direct N₂O emission rates, especially for poultry. The total GHG emissions in CO₂ equivalent units (CO₂e) were in the range from 6436 to 31839 g CO₂e d^-1 AU^-1. Poultry operations had much lower CH₄ emissions than ruminants but had higher N₂O emissions. In poultry operations, contributions of N₂O to total GHG (19.5% to 21.9%) were much larger than contributions of CH₄ (1.2%). In ruminant operations, contributions of CH₄ (18.5% to 44.4%) were more important than contributions of N₂O (1.7% to 16.2%). Swine operations had relatively low emissions of both N₂O and CH₄; therefore, their total GHG emissions were lowest compared with ruminants and poultry operations. Lower N diets had no significant effect on CH₄ and direct N₂O emissions, although they resulted in lower N excretion and therefore could reduce NH₃ and indirect N₂O emissions. Diet modification related with distillers dried grains with solubles (DDGS) and different feed ingredients could significantly affect CH₄ emissions, which merits further investigation for both ruminant and non-ruminant species.