Using Spirulina (Limnospira platensis) as an alternative feedstuff for poultry: Effects on ammonia and greenhouse gas emissions from excreta during storage

To identify sustainable alternative solutions to soybean meal, novel feedstuffs have been extensively investigated. Among these, Spirulina stands out due to its interesting composition and widespread use in animal nutrition. It is also well-known that animal excreta contribute significantly to global greenhouse gases (GHG), particularly ammonia (NH₃) emissions. The latter are particularly affected by storage conditions and excreta intrinsic characteristics namely pH, which can lead to increased Nitrogen losses. This study investigates the impact of including an alternative protein source, specifically Spirulina at a 15 % inclusion rate on chicken feeding, on GHG and ammonia NH₃ emissions during excreta storage. Two slow-growing broiler strains (naked neck and fully feathered) were raised under either thermoneutral (23 °C) or heat stress (30 °C) conditions. Each feeding trial lasted 12 weeks, during which excreta were collected, frozen, and later stored at ambient temperature for 60 days. A total of eight excreta types, each with three replicates, were analyzed. Results showed that excreta from birds raised under heat stress (30 °C) exhibited greater NH₃ and CO₂ emissions compared to those under thermoneutral conditions. Spirulina inclusion significantly increased NH₃ emissions by 11 % compared to normal diet and nitrous oxide (N₂O) by 17 %, regardless of temperature. Methane emissions remained low (< 0.075 µg/kg) across all treatments and were not significantly affected by diet nor temperature. Spirulina offers potential as a sustainable protein source; however, the inclusion level evaluated in the present study (15 %) was associated with increased nitrogen losses during manure storage, suggesting that high inclusion rates may increase the environmental footprint of broiler production.