Hydrogen sulfide emissions from a swine building affected by dietary crude protein

Hydrogen sulfide (H₂S) is a toxic air pollutant at animal facilities; but the understanding of its generation and emission processes has been limited. This paper studied H₂S emissions during a complete cycle of wean-finish pigs from a research building, where 12 pig rooms were divided into three groups that were fed with standard feed (control), and 2.1-3.8% (T₁) and 4.4-7.8% (T₂) reduced dietary crude protein (CP) feed. The group cycle mean H₂S emission rates were 4.0 ± 2.9, 4.3 ± 3.2, and 5.4 ± 4.0 g d^-1 AU^-1 (Animal Unit = 500 kg live mass), respectively, for the control, T₁, and T₂ groups. Emissions of H₂S were promoted by 10.0 and 36.7%, respectively, for the T₁ and T₂ groups (p < 0.001), although large variabilities existed in the emissions from different rooms within the same groups. The enhanced H₂S emissions from the T₁ and T₂ groups were related to the reduced manure pH and were possibly affected through a number of pathways, which could involve volatile fatty acids and nitrogen concentrations, and microbial activities in manure.