Reef is only 6 months old and was due to be moved with his mum to the stud where he was conceived. Despite having cooperated with loading in the past, Reef associated it with pain due to injuries - the reason why he'd been travelled before now. Prior to this video Reef had been subject to what became a highly pressurised and frightening situation, just to get him and mum to he stud. That attempt failed. Here is his retraining progress just days after.

http://www.youtube.com/watch?v=NE-JNYPwqKI&feature=youtu.be