When a horse is fed excessive amounts of carbohydrates over a short period, the small intestine may struggle to cope with the digestion, allowing some carbohydrates to escape digestion and move into the hindgut where they are fermented into fatty acids. Some fatty acids will be utilised as energy, but due to their high levels the pH of the hindgut drops allowing lactic acid producing bacteria to thrive. The build-up of lactic acid causes hindgut acidosis and eventual laminitis, which is the failed attachment of the distal phalanx to the hoof wall. This often leads to lameness and euthanasia as a result. Lactic acid producing bacteria Streptococcus equinus and Mitsuokella jalaludinii have been found to produce high amounts of L-lactate and D-lactate, respectively. This project will develop an impedance based DNA hybridisation biosensor to specifically detect these bacteria and provide early screening for hindgut acidosis to help prevent laminitis.

In the chosen bacteria, 16s rRNA sequences were identified and modified to obtain target ssDNA (single stranded DNA). Complementary ssDNA was designed from the modified target sequences to form capture probes. Binding between capture probe and target ssDNA in solution has been indicated by gel electrophoresis and binding together on a gold surface has been indicated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Moving forward, the aim is to optimise the hybridisation on gold and, in the future, the goal is to scale down the process onto a portable field ready device such as the PalmSens, so the tests can be performed conveniently and frequently at the horse’s location.