The investigation, carried out by animal rights filmmaker Joey Carbstrong, also showed sheep jumping barriers to try to escape as they were thrown or dragged into the restrainer before being killed.

On this week's episode: big bird intelligence, astronauts should jump, sheep and human history, and a tiny great ape.

The investigation, carried out by animal-rights film-maker Joey Carbstrong, also showed sheep jumping barriers to try to escape as they were thrown or dragged into the restrainer before being killed.