Resistors and capacitors calculation for 555 timer circuit
For timing in the hours, and if you really don't want to use a microcontroller, you could consider using something like a CD4060, which contains an oscillator and digital divider chain. You could also use a 555 and a counter such as a CD4040, but the 4060 has it all on one chip. 

Here's one example circuit. 



If you increase the value of C1 to 2.2uF you'll get 10x the times shown. 

You may want to trigger another timer (such as a 555) monostable to provide a pulse for the feeder. 

One advantage of the divider chain is that if you want to calibrate the time by using an adjustable resistor (trimpot) you can look at the timing on the earlier divider stages and not have to wait hours for each incremental adjustment of the time. 

It's not necessarily impossible to achieve timing in hours with a 555, especially a CMOS type, but it's not very easy or rewarding.