Employee was taking a load of manure to the manure pad to dump it. In the process of raising the trailer, the manure load froze while both of the safety latches at the bottom of the tailgate were still engaged. The employee exited the trailer and began to walk around the trailer to see why the load hadn't released. As he got near the tailgate, the manure load let loose and broke the two safety latches (1-1/4" steel rod), blowing the tailgate open. The bottom of the tailgate hit him in the leg. The employee suffered a fracture to the left thigh due to impact. Employee was transported to Backus Hospital and admitted.