Bits Can Interfere With Swallowing
While it's commonly believed that wearing a bit induces a horse to salivate, there's some concern that a bit interferes with a horse's ability to swallow. Researchers at Michigan State University have now measured how much a bit actually affects a horse's swallowing of saliva. They've discovered that various types of bits do behave differently.
The study assessed horses when cantering while wearing side reins to keep their poll in a flexed position. The bit and bridle arrangements compared in the cantering horses included a bitless bridle, a jointed snaffle bit and a Myler correctional-ported barrel bit.
How often the horses swallowed while cantering actually varied considerably among the 12 horses studied. The type of tack they wore also influenced their swallowing.
None of the bits prevented the horses from swallowing while cantering. But the horses swallowed less frequently while wearing the Myler snaffle compared with the other bits, or the bitless bridle.
J. Manfredi, H.M. Clayton and F.J. Derksen. 2005. Effects of different bits and bridles on frequency of induced swallowing in cantering horses. Equine and Comparative Exercise Physiology. 2: 241-244.