Effects of slatted floor fermentation bed on gas emissions and microbiological mechanism during fattening lamb breeding
In this study,we aimed at investigating how the slatted fermentation bed impacts ammonia(NH3)and greenhouse gas emissions,we thus constructed two animal pen types:ground floor and slatted floor and fermentation bed,then investigated the NH3,N2O,CO2,and CH4 emission characteristics as well as the microbiological mechanisms during fattening sheep breeding using metagenomics.Compared to the ground control,the fermentation bed could significantly reduce the NH3 emissions(P<0.05),exhibiting NH3 emission rates ranging between 21.64-58.92 mg·m-2·h-1,cumulative NH3 emission of 86.36 g·m-2,and a reduction rate of 58.60%.The slatted floor fermentation bed could also significantly reduce the CH4 emission rates(P<0.05),with a cumulative CH4 emission of 26.66 g·m-2 and a reduction rate of 64.42%.However,the slatted floor fermentation bed could significantly increase the N2O and CO2 emissions(P<0.05),especially those of N2O,yielding 190.84 times higher values than those of the ground control.The metagenomic analysis results revealed that the relative abundance of beneficial microorganisms,such as that of Salinicoccus,Corynebacterium,Brachybacterium,and Nocardiopsis,displaying salt tolerance and being involved in nitrification and denitrification,significantly increased in the fermentation bed(P<0.05).Moreover,the relative abundance of key nitrogen conversion genes,such as that of narG,napA,nirS,nirK,norB and nosZ,significantly increased(P<0.05),reducing the NH3 but increasing the N2O emissions of the fermentation bed.Compared with the ground control,certain anaerobic microorganism populations,such as those of Anaerococus and Anaerococus,were significantly reduced(P<0.05)in the fermentation bed,yielding lower CH4 emissions.In addition,the higher CO2 emissions of the fermentation bed were closely related to microbial pyruvate metabolism and tricarboxylic acid cycling.
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