On June 8, 2003, at 1100 central daylight time, a Robinson R-22 Beta helicopter, N854WT, was substantially damaged when it collided with a tree while maneuvering near Encinal, Texas. The commercial pilot, who was the sole occupant of the helicopter, was not injured. The helicopter, registered to and operated by Smith Helicopters, Inc., of Laredo, Texas, was operating under 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and a flight plan was not filed for the cattle herding flight. The flight originated from a local staging area, approximately 0930. The 1,500-hour pilot reported in the Pilot/Operator Aircraft Report (NTSB Form 6120.1/2), that after gathering and penning cows for an hour and a half, he spotted a bull not far from the cattle pens. He was trying to herd the bull through a gate, and was able to stop the bull while hovering about 5-10 feet agl. The pilot further reported that the bull suddenly started to run underneath the helicopter and he "pulled out of the way to avoid the bull." Subsequently, he "felt the helicopter contact some brush" and executed a 180-degree pedal turn when he "felt the helicopter begin to vibrate." He then executed an auto rotational landing. Examination of the helicopter by an FAA inspector, who responded to the accident site, revealed that the aft section of the tail boom was separated, the tail rotor blades were damaged, and the tail rotor drive shaft was severed.