Ammonia (NH3) emissions from swine manure are a major contributor to livestock odor and air pollution. In this study, the urease inhibitor Phenyl- Phosphorodiamidate (PPDA) was applied as a preventive control strategy, and its reduction efficiency was evaluated through both chamber simulations and a pilot-scale pig house experiment. The chamber experiment, conducted from March 17 to May 1, 2023, showed that the treatment group receiving both urea and PPDA (P1) exhibited a 53% lower mean NH3 concentration (51.1±15.1 ppm) compared with the urea-only group (U1, 109.0±34.0 ppm; p < 0.001). The maximum concentration was also reduced by 63.8% (245.1 ppm in U1 vs. 88.8 ppm in P1). Dose-dependent tests revealed that reduction efficiency increased with PPDA dosage (1.0 g, 32.3%; 0.5 g, 27.3%; 0.1 g, 21.1%), but gains plateaued beyond 0.5 g, suggesting economic feasibility at intermediate levels. The pilot-scale experiment, conducted in a mechanically ventilated pig house from May 13 to August 2, 2024, confirmed the short-term effectiveness observed in the chamber tests. During the first application period, the treatment group (P5) maintained approximately 50% lower NH3 concentrations than the control group (C2). However, the effect decreased to less than 5% during the second period, and concentrations converged with or exceeded those of the control group during the finishing stage. This decline was attributed to factors such as insufficient slurry mixing, dosage mismatch due to an increase in body weight, and physicochemical changes in the slurry environment. These findings indicate that PPDA effectively suppresses urea hydrolysis and reduces acute NH3 peaks, thereby functioning as a preventive mitigation strategy. Although its long-term efficacy under field-like conditions was limited, optimization of dosage, re-application intervals, and slurry management could enhance performance. Overall, this study demonstrates the potential of PPDA to shift livestock odor management from conventional end-of-pipe approaches toward preventive control strategies, providing a scientific basis for integrated and sustainable odor mitigation.

The objective of the present study was to investigate the effects of different red seaweeds on in vitro rumen fermentation characteristics and methane gas production. Five species of red seaweed (Chrysymenia wrughtii Yamada, CW; Hypnea sp., Hypnea sp.; Chondria crassicaulis, CC; Gelidium vagum Okamurae, GV; Hypnea saidana Holmes, HS) were obtained from National Institute of Fisheries Science (NIFS) in South Korea. The collected red seaweeds were washed for 3 minutes, and then samples were freeze-dried and ground to a size of a 1 millimeter. The buffered ruminal fluid (50 mL) was incubated with substrates and seaweeds (5% of substrates) at 39℃ for 48 hours. Total gas production was lower than red seaweed treatments excluding the CW treatment (p<0.05; 63.25 mL). Methane production was the lowest in CC treatment (p<0.05; 9.93 mL/g of digestible dry matter). The rumen pH of the red seaweed treatments ranged from 5.98 to 6.08, which was significantly the lowest in the GV treatment (p<0.05; 5.98). There was no significant difference in the total VFA concentration, but propionate (27.53%) was significantly highest in the CW treatment, whereas acetate (53.14%), iso-valerate (3.52%), valerate (1.72%), and A:P ratio (1.93) were significantly lowest (p<0.05). In conclusion, among the five species of red seaweeds, Chondria crassicaulis reduced in vitro methane production without negative effects on dry matter digestibility. Future studies will be needed to determine the optimal inclusion level of Chondria crassicaulis as feed additive to reduce enteric methane production.