You can definitely tell a difference with grassfeed fat.  I love it.

Quoting David Harrison <[log in to unmask]>:

> I have been eating mainly grass-fed beef and lamb for awhile now. I  
> bought a quarter cow from a local guy.
> When I cook a roast and let it (with the juices) get cold, the fat  
> hardens like butter/ coconut oil type consistency. That hardened fat  
> tastes very good to me and feels very good to eat.
> I also have not eaten any grains for quite awhile.
> Recently my wife made a roast from a commercial source butcher shop.  
>  When the leftovers got cold, the resulting hard fat tasted off.  I  
> tossed the hardened fat.
> Just a personal observation.
> -David
>