Microbial agent spraying in pig housing and slurry can potentially reduce harmful gas emissions - a preliminary study

Abstract

This study aimed to evaluate the effects of spraying microbial agents in pig slurry and housing on harmful gas emissions. A total of 300, eight-week-old crossbreed ([Yorkshire × Duroc] × Landrace) growing pigs, with an average body weight of 28.2 ± 0.55 kg were used in this trial lasting 4 weeks (28 days). Experiment 1: pigs were randomly assigned to two treatments and housed in two separate rooms (150 heads/room). Slurry stored in a slurry pit, produced by growing pigs housed in one room, was sprayed with Bacillus subtilis (TRT1), while slurry from the second room was sprayed with Lactobacillus plantarum (TRT2). The results showed that L. plantarum had a better limiting effect on ammonia (NH3), hydrogen sulphide (H2S), and carbon dioxide (CO2) concentrations (P = 0.01, P = 0.03 and P = 0.01 respectively) than B. subtilis. After Experiment 1, the pigs were rearranged and transferred to finishing rooms. At this point, they were subdivided and housed in 3 separate rooms consisting of 100 pigs each (Experiment 2). Subsequently, their slurry pits were sprayed with or without a mixture of microbial agents (B. subtilis and B. licheniformisis) as follows: CON (no microbial agents), BSBL1 (mixed microbial agent spray 1000:1) and BSBL2 (mixed microbial agent spray 1000:2). In Experiment 2, we observed that the gases, i.e. NH3, H2S, total mercaptans, acetic acid, and CO2 were strongly reduced with increasing levels of the microbial agent. Our findings clearly indicated that spraying L. plantarum in slurry exerted a greater effect on odorous gas emission compared to spraying B. subtilis. Moreover, the microbial spray mixtures provided improved positive outcomes possibly as a combined effect compared to solitary sprays.