On November 4, 2001, at approximately 1640 mountain standard time, a Piper PA-28-235, N4447D, was substantially damaged when it struck a deer during a touch-and-go landing at North Fork Valley Airport, Paonia, Colorado. The private pilot and his passenger were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for this personal flight being conducted under Title 14 CFR Part 91. The flight originated at Gunnison County Airport, Gunnison, Colorado, at approximately 1507. According to the pilot, he departed Gunnison on a sight seeing flight over Blue Mesa Reservoir and Black Canyon National Park, on the way to the final destination in Eagle, Colorado. While en route, the pilot decided to do a touch-and-go landing at North Fork Valley Airport. The pilot stated that he did not see any deer on the runway. However, just after rotation, a deer appeared in his path, and the airplane struck the deer with its left wing, tearing off the left main landing gear assembly. The pilot continued the initial climb and tried to contact someone on the ground to assist him in identifying the damage. He was unable to contact anyone and decided to continue the flight to his destination. Approximately 10 miles west of Eagle County Regional Airport, Eagle, Colorado, he called and advised the tower that he had hit a deer at North Fork Valley, and requested a low pass to have someone check his landing gear. The tower informed him that his left main landing gear was missing. At approximately 1700, he landed the airplane on runway 07, with approximately 6000 feet of runway remaining. The airplane's left wing tip struck the ground, and the airplane slid off of the north side of the runway. The airplane sustained substantial damage to the left wing spar at the main landing gear attachment point, the left main landing gear assembly, and left horizontal stabilizer.