# Practical microalgal supplementation: reducing ammonia emission from manure in commercial layer production

## TL;DR

Adding microalgal powder to laying hen feed significantly reduces ammonia emissions from manure by altering microbial communities and nitrogen metabolism.

## Contribution

This study demonstrates that compound microalgal powder effectively reduces ammonia emissions in commercial layer production through microbial and metabolic regulation.

## Key findings

- Compound microalgal powder reduced ammonia emissions by 40.47%–77.84% within 24 hours.
- The powder reshaped the microbial community, reducing ammonia-producing bacteria and increasing acid-producing bacteria.
- Spirulina platensis was most effective, with phycocyanin mitigating Gram-negative bacteria activity.

## Abstract

The rapid development of intensive layer breeding has intensified odor pollution that must be paid attention to for the green transformation of the industry. This study used Jingfen No.6 laying hens as the model to systematically evaluate the regulatory effect of compound microalgal powder (Chlorella vulgaris:Spirulina platensis:Haematococcus pluvialis = 3:1:1, 1:3:1, 1:1:3) on ammonia (NH3) emissions from laying hen manure.

Through analysis of the static NH3 production in manure, it was found that the NH3 emissions within 24 h in the experimental group with 0.50% compound microalgal powder added were reduced to 6.27–16.84 mg (vs. control: 28.29 mg), achieving a 40.47%–77.84% reduction. GC/MS and 16S rRNA sequencing analyses indicated that the compound microalgal powder intervened in the remodeling of the microbial community and nitrogen metabolism network in manure, driving the transformation from inorganic nitrogen to organic nitrogen, mitigated the proliferation of NH3-producing bacteria (such as Escherichia coli, Klebsiella pneumoniae, Kurthia, and Proteus), and increased the abundance of acid-producing bacteria (such as Leuconostocaceae and Lactobacillaceae). The Spirulina platensis powder group had the best emission reduction effect (reduced by 77.84%), and its mechanism was closely related to the mitigation of Gram-negative bacteria activity by phycocyanin and increased synthesis of aromatic compounds, such as 2,3,5-trimethyl-6-ethylpyrazine.

This study revealed the mechanism by which the compound microalgal powder reduces NH3 emissions by regulating the proliferation of acid-producing bacteria, reshaping the nitrogen metabolism network, and mitigating the activity of NH3-producing bacteria, while providing theoretical and data support for the development of environmentally friendly feed.

The online version contains supplementary material available at 10.1186/s40104-025-01264-z.

Dietary supplemental microalgal powder reduces NH3 emissions from laying hen manure.Nitrogen deposition and transformation in manure regulate NH3 production.Mitigation of NH3-producing bacterial proliferation was the primary mechanism.Kurthia and Proteus were identified as principal NH3-producing bacteria.Lactobacillaceae and Leuconostocaceae mitigates the NH3 emissions.

Dietary supplemental microalgal powder reduces NH3 emissions from laying hen manure.

Nitrogen deposition and transformation in manure regulate NH3 production.

Mitigation of NH3-producing bacterial proliferation was the primary mechanism.

Kurthia and Proteus were identified as principal NH3-producing bacteria.

Lactobacillaceae and Leuconostocaceae mitigates the NH3 emissions.

The online version contains supplementary material available at 10.1186/s40104-025-01264-z.