Trace elements in struvite equine enteroliths: Concentration, speciation and influence of diet.

The research article presents a thorough examination of the growth processes, composition, and trace metal accumulation mechanisms in equine enteroliths — a condition found in horses, characterized by the formation of stones in the gastrointestinal tract. The study suggests that these insights could be pivotal in managing and preventing the condition in the future.

Study Methodology and Findings

• The research team collected enteroliths approximately 1.5cm in diameter from an Arabian horse in Louisville, Kentucky.
• Upon conducting Scanning Electron Microscopy (SEM) and light microscope imaging of a sectioned enterolith, two distinctive regions of concentric growth were observed from the central nidus — a small pebble.
• They noted a process where the acidic colonic fluids of the horse permeated the stone, causing a recrystallization of crystals closest to the nidus. When mineral crystallization became favorable again, a second growth of unaltered crystals transpired at the rim.
• They identified the mineral as struvite (MgNHPO∙6HO) through powder X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy.
• Elemental analysis confirmed concentrations of phosphorous, magnesium, and nitrogen consistent with the struvite composition, and detected trace elements such as iron, manganese, and Zinc. All these elements were linked to dietary sources.
• The researchers used X-ray absorption fine structure (XAFS) spectroscopy to uncover that distorted ZnO tetrahedra are located between crystallographic planes in the struvite structure, forming bidentate linkages to struvite phosphate groups.

Practical Implications and Conclusions

• The study found the Fe:Mn:Zn ratio of the enterolith to be consistent with that of the horse feed, providing evidence that diet can significantly influence the formation and composition of these enteroliths.
• Trace elements and organic impurities are suggested to increase the enteroliths’ susceptibility to heat-induced decomposition when compared to pure struvite. This understanding could prove useful in formulating treatments for the condition.
• The research results offer comprehensive insights into the processes of equine enterolith growth, shedding light on the potential diet-related factors influencing it. Such understanding could be crucial for the development of effective prevention and management strategies for equine enteroliths.