These are nice articles, that makes me feel like I am doing the right thing for my old men.

http://www.horsechannel.com/horse-health/improve-older-horse-1733.aspx

http://www.horsechannel.com/horse-health/senior-horse-care-24341.aspx

http://www.vetmed.ucdavis.edu/ceh/docs/horsereport/pubs-HR24-3-bkm-sec.pdf