The Hygienic Status of Different Forage Types for Horses—A Retrospective Study on Influencing Factors and Associations with Anamnestic Reports

The hygienic quality of forage for horses is discussed as a potential health hazard, especially regarding respiratory diseases, colic, and hepatopathies. Therefore, the purpose of this study was to investigate the possible relations between microbiological counts, as well as endotoxin levels and disease symptoms. Data from microbiological examination reports were analyzed retrospectively, including the results of sensory examination, microbiological counts, and lipopolysaccharide contents. Sensory analysis gave an indication of deficiencies in microbiological analysis, but both methods did not give consistently equivalent results regarding the hygienic status of forage. The strongest agreements between sensory and microbiological findings were demonstrated in haylage regarding mold contamination. The influences of dry matter content on microbiological quality could be shown in haylage and hay, whereas this did not apply to straw. Deviations regarding molds and the detection of Aspergillus species occurred, especially in haylage, with values above 70% DM detected (39.6%, p=0.0021 and 47.2%, p = 0.0393). Aspergillus was detected more frequently, and average counts were higher in samples that were suspected to induce coughing in horses (p = 0.0118 and p = 0.0313, respectively). The results of the present study emphasize the importance of feed hygiene for equine respiratory health and the need for the microbiological examination of feedstuffs, since sensory analysis cannot provide an error-free prediction of microbial counts.