Metal analysis of horse bits using X-ray fluorescence (XRF)

Stainless steel and different brass alloys are materials commonly used for bits in equestrian sports. Sweet iron bits for horses are the current trend as they develop superficial rust which tastes sweet and enhances the horse’s saliva production. This study focusses on the metal analysis of different bits (n = 103) using X-ray fluorescence (XRF) spectrometry. The analysed elements were clustered statistically in order to define different alloy groups with specific element ranges. In a field test, changes in the iron content and weight losses of both sweet iron (n = 10) and conventional (n = 9) metallic bits due to normal wear were analysed over 90 days. Fourteen chemical elements accounted for at least 97.07 % (median: 99.85 %, mean: 99.70 %) of the weight of the bits. Of the 103 bits studied, 93 could be attributed to one of the six principal alloy groups identified by the statistical clustering method. Copper and zinc were important elements in the definition of the alloy groups and their proportions characterised most of the bits. During 90 days of normal wear, no significant variation of the percentage iron content of the bits was observed, neither for the conventional bits (p = 0.53) nor for the sweet iron ones (p = 0.41). However, significant weight losses occurred in both groups, averaging 0.28 g (p = 0.04) in the conventional group and 0.2 g (p = 0.02) in the sweet iron group. Based on the results of the metal analysis by XRF and the field test carried out to observe changes occurring during normal wear, there is no reason to expect a toxic release of iron into the horse’s mouth from sweet iron bits.