Microalgal Feed Additives Cut Ammonia Emissions in Laying Hen Production by Up to 78%

A new study published in Journal of Animal Science and Biotechnology demonstrates that compound microalgal supplementation can dramatically reduce ammonia (NH₃) emissions from laying hen manure—achieving reductions of 40.47% to 77.84% depending on formulation. The findings offer a promising, environmentally friendly feed-based strategy for poultry farms struggling with odor pollution and nitrogen emissions.

Researchers used Jingfen No.6 laying hens and tested three microalgal combinations containing Chlorella vulgaris, Spirulina platensis, and Haematococcus pluvialis at a 0.50% inclusion rate. Across all treatments, cumulative 24-hour ammonia emissions decreased significantly compared to the untreated control.

Spirulina-rich formulas performed best

The microalgae mixture with the highest proportion of Spirulina platensis produced the greatest reduction—up to 77.84% less ammonia than controls. The study attributes this effect to:

suppression of Gram-negative ammonia-producing bacteria including Escherichia coli, Klebsiella pneumoniae, Kurthia, and Proteus
bioactive compounds such as phycocyanin, known for antibacterial and antioxidant properties
increased synthesis of beneficial nitrogen-containing aromatic compounds (e.g., 2,3,5-trimethyl-6-ethylpyrazine)

Microalgae reshape manure microbiota and nitrogen metabolism

Using GC-MS flavor omics, qPCR, and 16S rRNA amplicon sequencing, the researchers showed that microalgal supplementation:

shifted inorganic nitrogen (NH₄⁺-N and NO₃⁻-N) toward organic nitrogen, rather than allowing it to volatilize as NH₃
increased the abundance of acid-producing bacteria such as Leuconostocaceae and Lactobacillaceae
decreased key NH₃-producing taxa like Oscillospiraceae and Erysipelotrichaceae
downregulated nitrogen-cycle genes associated with nitrous oxide formation

These microbial and biochemical changes reduced manure pH and supported nitrogen retention, thus limiting ammonia volatilization.

Implications for sustainable poultry production

The study provides the first detailed mechanistic evidence that multi-species microalgal powders can regulate manure nitrogen pathways through a “microbial–metabolite–NH₃ interaction network.” The authors note that all three tested formulations—Chlorella-rich, Spirulina-rich, and Haematococcus-rich—show clear mitigation potential, though Spirulina-based mixtures offer the strongest effect.

The results offer a scalable feed-based strategy for improving environmental performance in commercial layer operations and open new directions for eco-friendly feed additive development.

Reference

Yu, Z., Ma, X., Long, T. et al. Practical microalgal supplementation: reducing ammonia emission from manure in commercial layer production. J Animal Sci Biotechnol 16, 140 (2025). https://doi.org/10.1186/s40104-025-01264-z