Catherine Clappison, UCBB.

 

This study was shortlisted for the 2022 Thesis of the Year Award and completed as part of Catherine’s BSc(Hons) Bioveterinary Science, which she studied at University Centre Bishop Burton.

Take home message: Fungal contamination in straw bedding and air varies across different farms and is affected by numerous factors including age of pigs, stocking density and climate. Farmers should consider these factors when managing pig housing and bedding to reduce risk of respiratory disease. Further research could focus on how to reduce fungal contamination at harvest and during storage of straw.

Straw is a commonly used bedding material for pigs due to the increased enrichment provided in comparison to more intensive systems such as slatted flooring. However, straw requires more upkeep to maintain good hygiene and has been associated with increased dust levels; a risk factor for respiratory disease. A related risk factor is contamination of fungi which, with the mycotoxins they produce, can be harmful to livestock and humans.

The aim of this project was to assess fungal contamination across three ‘bed and breakfast’ pig farms by quantifying colony forming units (CFUs) on agar plates. Higher numbers of CFUs indicates increased fungal contamination. Within each farm, 2-3 pig sheds were sampled from and three sampling groups allowed for different areas to be tested on each farm:

• Outdoor control plates were placed away from pig sheds on each farm to identify any fungal growth in outdoor air

   

• Passive air was assessed by placing open plates inside the pig sheds at a height of 1.2m to avoid interference from the curious pigs and quantify the airborne contaminants in each shed

   

• Bedding was directly sampled from each pig shed and diluted in the lab to quantify contaminants within the straw bedding

   

The results highlighted significant differences in fungal CFUs between each farm for passive air and bedding measurements, as well as significant differences between the passive air and control air, and bedding and control air. This highlights variation in air quality between different farms despite all farms using wheat straw from a 2021 harvest. Associations were found between the airborne CFUs and stocking density, age of pigs, dew point (a weather metric accounting for humidity and pressure), and dust level. This suggests these factors could be the reason for farms having different air quality. Further investigation is needed to accurately determine the impact of each of these factors on air quality, but previous literature suggests growing/fattening pigs produce much higher CFUs than nursery or farrowing pigs (Kim & Ko, May 2019. Asian-Australas J Anim Sci.). There was no difference between sheds on the same farm, suggesting that housing was consistent at each location.

These findings suggest that a range of housing variables and microclimatic factors impact air quality at straw bedded pig farms. Farmers are encouraged to weigh the pros and cons on an individual basis as optimal management may be different for each herd and if using a straw bedding system, ensure quality of straw and appropriate stocking density is a priority to limit risk factors for respiratory disorders as much as possible.

Georgie Smith is a PhD candidate in the School of Biology, University of Leeds.