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

Abstract

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.