Can i put a stable rug under a turnout rug?
Why? I've always felt that the less clothing I pile upon my horses, the better.
It's best to have a nylon material against your horse. Most blankets are lined in nylon sheeting and they advertize it as polishing the coat. Cotton or wool may be a bit more comfy, but it pulls and catches the fur making the big movements in turnout likely to rip it. That's why they are used inside the stable.
You can, but it's something reserved for the winter. My pony has a hunter clip in the winter and will be turned out with a heavyweight t/o rug with a neck. If not too cold, he may just have that on. If a little chilly, we just use a fleece as a liner rug. If cold with a cold wind chill or it's so cold it's a bit icy, he tends to have his duvet-type under rug left on under the heavyweight. He's the type that gets very very cold very quickly in the winter and he also has allergic bronchitis, which catching a chill can aggravate, so we layer rugs for prevention. He also goes out all day, so has the extra rug in case the temperature drops (our yard is on top of a small hill so tends to be very cold and breezy in the winter, with the temperature dropping occasionally throughout the day)