Impact of Ammonia Exposure on the Enteric Nervous System in the Ileum of Pigs From Birth

Background: Best Available Techniques have been introduced in the EU to counteract pollution related to intensive farming and its effect on the health of animals and workers. It is known that high levels of ammonia (NH3) worsen the productive performance of animals, but the exact mechanism of interaction with the intestine is still unknown. Therefore, this study aimed to investigate the effect of NH3 on the gut of pigs exposed to different levels since birth. Methods: Two farms with different manure removal systems were considered (Recirculation and Vacuum), where two different NH3 levels were detected: high and low ammonia (recirculating slurry system, RS, and vacuum slurry system, VS, respectively). The entire production cycle was considered, and a fecal score and microbiological analyses of the feces were performed. After slaughtering, the ileum of 12 animals was sampled to evaluate ileum morphology and the expression of some neurotransmitters. Key Results: No differences were found in Peyer's patches morphology. The mucus layer thickness was higher, and the acidic mucins were lower in the RS animals. Results revealed changes in the number and area of neuronal and glial cells, and an upregulation of choline acetyltransferase (ChAT) and galanin (GAL) genes was observed. Conclusions and Inferences: The alteration of the Enteric Nervous System (ENS) highlighted a connection between high levels of environmental NH3 and neuroplasticity. Furthermore, the upregulation of ChAT and GAL genes suggests a key role in visceral pain, creating a link between peristalsis and chronic diarrhea observed in healthy pigs. Lastly, these findings are important for both animal health and human workplace safety.