On July 1, 2011, approximately 1100 central daylight time, a Piper PA-28-180, N56417, was substantially damaged when it impacted a bale of hay during a forced landing near Flippin, Arkansas. The pilot was seriously injured. The airplane was registered to Mid-South Specialty Construction LLC., and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the cross-country flight which operated without a flight plan. The flight originated from Mountain Home, Arkansas, and was en route to Marshall, Arkansas. According to the pilot, he was in cruise flight when he noted a decrease in engine rpm. The pilot began to troubleshoot the decrease and reversed course to head towards more favorable terrain for a forced landing. After completing the turn, the engine seized. The pilot performed a forced landing to a pasture. During the landing roll, the right wing impacted a bale of hay, separating the right wing from the fuselage. A Federal Aviation Administration inspector reported that the airplane had just undergone maintenance. An examination of the engine revealed that the loss of engine power and resultant seizure was due to a loss of engine oil. Further examination revealed that the bolts on the vacuum pump were loose and the engine oil was exiting at this location. An examination of the airframe and remaining systems revealed no anomalies.