I can remember watching that (think probably on the TV) back in 2006 (didn't realise it was that long ago!). Incredibly brave horses and riders. I didn't find it so emotional first time round but I think watching it with that music is to do with that!
I think they were farmed for meat. However no animal deserves to die of drowning or left in such a horrendous situation. Have seen this video several times before and always makes me cry. I am a soppy cow.