It is well understood that gaseous ammonia is harmful to pig health and productivity. Exactly how ammonia causes these harmful effects is not understood as well. Researchers used 24 separate controlled atmospheric chambers to house total of 120 Duroc×Landrace×Yorkshire pigs. The pigs were continuously exposed to gaseous ammonia at 0,5, 10, 15, 20, and 25 ppm for 4 weeks. High-throughput genetic sequencing was used to perform 16S rRNA gene analysis in nasal swabs samples from 72 pigs (n = 12). The results of the nasal microbiota analysis showed that an increase in ammonia concentration, especially at 20 and 25 ppm, decreased the diversity and relative abundance of nasal microbiota. Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, and Chloroflexi were the most abundant microbial families. Pseudomonas, Lactobacillus, Prevotella, and Bacteroides were significantly decreased at 25 ppm, while Moraxella and Streptococcus were increased at 25 ppm. An increase in ammonia levels, especially an ammonia level of 25 ppm, caused respiratory tract injury while simultaneously decreasing respiratory immunity and growth performance.
Ammonia treatments at 0–10 ppm resulted in a relatively intact tracheal mucous membrane structure. In the 15–20 ppm ammonia environment, the cilia of the tracheal mucosa were moderately deteriorated. In the presence of 25 ppm ammonia, the structure of the tracheal mucosal layer was severely deformed, and the columnar cilia of the pseudostratified layer were also largely absent.
The following changes were noted at different levels of ammonia in the air:
> 10 ppm increased blood ammonia and urea nitrogen concentrations and decreased the antioxidant ability of pigs.
> 15 ppm affected the expression of genes related to the integrity of the trachea structure (wind pipe)
> 20 ppm r educed the levels of antibodies (immunoglobulins) in the mucosal lining of pig trachea .
> 25 ppm significantly damaged tracheal mucosa cilium (hairs) and decreased growth performance. A large number of inflammatory cells were found in the alveolar cavity, and severe reddening of the lung tissue
Take Home Message
Controlling ammonia levels in the pig barn is an important part of a disease control plan for both multi-systemic diseases (eg Glassers) as well as respiratory diseases (PRDC).
Increased ammonia concentration can alter the microbiota of the nasal passage and make pigs more susceptible to disease in multiple ways.
These researchers suggest a target for ammonia of 20 ppm but their research seems to confirm that it is wise to keep ammonia levels under 10 ppm.
Submitted by Brent Jones, DVM
Ref: Wang T, He Q, Yao W, Shao Y, Li J, Huang F. The Variation of Nasal Microbiota Caused by Low Levels of Gaseous Ammonia Exposure in Growing Pigs. Front Microbiol. 2019 May 16;10:1083. doi: 10.3389/fmicb.2019.01083. eCollection 2019