Can an IR camera be used in broad daylight?
It sounds like you are talking about Thermal Infrared, 10um - 14 um wavelength which corresponds to a black body temperature of 300 K.  This is what is typically used to image and detect the body heat of mammals.  The detector here are either MCT (Mercury Cadmium Telluride) cooled detectors or Bolometer based.

The answer is yes, the ambient visible light levels only affect the image in so much as there might be differential heating of exposed surfaces and those will appear hotter (which appears brighter).

In military systems for thermal targeting they use InGaAs detectors (3um - 5um) which corresponds to higher temperatures from exhaust plumes etc. But again operation in daylight is not an issue.