Yes. Look for cans w/ no added sugar or salt. I can't imagine they would pre-load it w/ "pumpkin pie spices" but all those things are safe too. They could also eat canned sweat potatos, if you could find any w/o added sugar.
Now, the caveat. Keep the amount offered SMALL. One typical can weights as much as four hen's entire feed for a day. You are offering a treat, not a meal replacement.
Chickens already get plenty of energy from the corn and other grains in their diet, and the fat in any seeds in their feed. Chickens don't benefit from high fiber diets the way we do. and if their feed is properly formulated, its already got the few vitamins in your pumpkin mash in sufficient quantity.
This isn't a diet enrichment for them, its entertainment for you and them. Keep that in mind.
