Mitigating ammonia emissions from dairy slurry storage by using brown seaweed in the diet for sustainable...

Livestock production is a major contributor to ammonia (NH₃) and greenhouse gases. Brown seaweed, Himanthalia elongata, contains bioactive compounds such as phlorotannins, which can influence protein digestion and potentially reduce NH₃ emissions from excreta. However, their impact on NH₃ emissions from dairy slurry during storage remains largely unexplored. This study evaluates the effects of H. elongata and its extract on NH₃ emissions from slurry when included in the diet of dairy cows. Nine late lactation multiparous Holstein-Friesian cows were fed three diets (dry matter basis) for 22 days: 1) control: 60% grass silage and 40% concentrate; 2) 4% H. elongata, 56% grass silage and 40% concentrate; and 3) 4% seaweed extract, 56% grass silage and 40% concentrate. Faeces and urine samples were collected separately from cows, combined at a 3:2 ratio to prepare 20 kg of slurry, and stored for six weeks to monitor NH₃ emissions using the static chamber method. Cumulative NH₃ emissions were significantly reduced in the H. elongata 733.70 ± 66.46 mg N/m²) and extract (996.71 ± 26.94 mg N/m²) treatments compared to the control (1379.64 ± 92.76 mg N/m²). These results highlight the potential of H. elongata as a sustainable solution for mitigating NH₃ emissions from slurry generated in dairy farming.