I have two dogs and german sheppard/chow mutt and a german sheppard/golden
retriever mutt. One is 11years old, the other 2 years old. Due to excess
work load (8am to 9pm) I have been unable to walk them and play with them on
a daily basis. They are in the backyard during the day (3/4 acre) so I know
they have room to run around and such, and I am too tired at nights to walk
them. Does anyone know of an automated way to keep them busy. I have
gotten then balls, bones, ropes to play with but am not sure that they do.

What do others do to keep them active in similar situations?