Reducing thumb extensor risk in laboratory rat gavage

Gavage is a common technique for orally administering compounds to small laboratory animals using a syringe. It involves highly repetitive thumb extensor exertions for filling the syringe, a risk factor for DeQuervain's tenosynovitis. As an intervention, a series of bench tests were performed varying fluid viscosity, syringe size and needle size to determine the forces required for drawing fluid. Forces up to 28 N were observed for a viscosity of 0.29 Pa s. A guide is presented to minimize thumb forces for a particular combination of syringe (3 mL, 5 mL and 10 mL), fluid viscosity (0.001 Pa s, 0.065 Pa s, 0.21 and 0.29 Pa s), and needle length (52 mm, 78 mm and 100 mm) based on maximum acceptable exertion levels. In general, a small syringe and large needle size had a greater number of acceptable rat gavages per day due to the lower forces experienced as compared to all other syringe and needle combinations.