What was the unconditional response in Pavlov's experiments with dogs?

In Pavlov's experiments with dogs, the unconditional response was the dogs' salivation when they were presented with food. This response occurred naturally and automatically without any prior conditioning, demonstrating the dogs' innate physiological reaction to the food stimulus. Pavlov's work illustrated how a neutral stimulus, like a bell, could be paired with the food to eventually elicit salivation through conditioning.