Horse feed hygiene evaluation with microbial and sensory examination

Abstract

Feed hygiene is an essential contribution to equine health and welfare. It can be assessed by sensory and microbiological analysis. The aim of this study was: (a) to compare these systems using the results of 171 horse feed samples, previously examined at the Chair of Animal Nutrition and Dietetics, Munich; (b) to compare the microbiological findings with the results of the sensory examination; and (c) to evaluate the relationship between hygiene scores and case history. Outcomes of the sensory examination (texture, odour, colour, contamination) were classified as either 'no', 'minor', 'moderate' or 'significant' hygienic deficiencies. The results of the microbiological analysis were evaluated by two methods: (1) quantitatively, and (2) both qualitatively and quantitatively. The germ counts were categorised in 2 groups as either 'adequate' or 'elevated' for comparison of the systems. Both systems scored 52% (n=88) of the feed samples as adequate, but 38% (n=65) of the feed samples had elevated counts for at least one of the germ counts. The qualitative evaluation (method 2) rated 10% (n=17) of the mould counts to be elevated indicating poor quality, while these were found to be 'adequate' by method 1. The latter graded the yeasts more strictly with seven elevated cases (4%) which were judged normal by method 2. The sensory score strongly correlated with yeast counts (P<0.05, R2= 0.79), but this is mainly due to a strong link with the 'elevated' score. Mould counts correlated with sensory scores (P<0.001, R2= 0.57). Samples sent in for airway related problems showed highest microbiological counts (54%). Both systems showed a strong agreement (90%) on the evaluation of microbiological analysis for horse feed which was the purpose of this study. Verification of the systems needs to further look at controlled measures from a more balanced variety of samples.