The Microbiological Quality of Concentrates for Horses—A Retrospective Study on Influencing Factors and Associations with Clinical Symptoms Reported by Owners or Referring Vets

SIMPLE SUMMARY: Poor feed hygiene is also referred to as spoilage and can be measured by means of determining growth of microorganisms (bacteria, mold and yeast). Evidence has been provided of mold spores triggering equine asthma, a chronic, non-infectious respiratory disease. Furthermore, a high yeast load is suspected to trigger gastrointestinal disorders (colic) in horses. One aim of the present study was to clarify the possible connection between certain equine diseases and poor feed hygiene. For this purpose, archived reports of hygiene examinations of concentrates for horses were processed statistically. Reports contained information on disease symptoms as reported by horse owners or equine practitioners, as well as results of sensory and microbiological analyses. Further assistance to horse owners and equine practitioners should be provided in evaluating health hazards emanating from poor feed hygiene. Another objective was to assess the possibility of detecting hygiene deficiencies by means of simple examination methods such as determination of dry matter content and sensory analysis in order to estimate the validity of these field methods. It was shown that a connection can be made between mold content of oats and coughing in horses, whereas no connection could be found between poor feed hygiene and equine colic or elevated liver enzyme activities. No significant predictability of poor feed hygiene by means of sensory analysis could be established, whereas a significant association between low dry matter content and mold contamination in grains was shown. ABSTRACT: Evidence has already been provided that feed-borne mold spores and endotoxins can trigger chronic, non-infectious respiratory disease if inhaled. Furthermore, deficiencies in feed microbiology are suspected to trigger gastrointestinal and liver disorders in horses, but the connection needs further clarification. Most of the previous studies regarding horse feed hygiene focused on forage, whereas research regarding hygienic quality of concentrates is scarce. In the present study, results of reports on hygienic quality of compound feed and cereals for horses were evaluated secondarily. Results included sensory findings, and counts of aerobic bacteria, molds and yeasts determined by cultivation and lipopolysaccharide (LPS) contents. It was found that microbial counts of compound feed exceeded VDLUFA orientation values significantly more frequently than cereals (38.4 vs. 22.6%). However, average counts of bacteria, molds and yeasts were higher in cereals than in compound feeds (p < 0.0001, respectively). Mold counts in grains were significantly higher if dry matter contents were below 86% (p = 0.0201). No relation could be established between the anamnestically reported gastrointestinal disorders or elevated liver enzyme activities and microbiological deviations. Mold counts of concentrates which were suspected to cause coughing in horses were significantly higher than mold counts of control samples (3.29 vs. 2.40 log(10) cfu g(−1), p = 0.0313). These results indicate that hygienic status of concentrates is relevant for horse health in the respiratory tract.