If I race my horses more at an early age are they likely to decline quicker? For example would there decline go on number of races had or actually age in years??

Danethan the red deterioration potential bar - http://postimg.org/image/8ku90dkgz/ is a good indicator of what stage in your horses career you are going to get the best out of it, if the bar is low as it is in the case of the great Hoof Prince then that means your horse will not peak at a young age and you will get a full career, if the red bar is high then your horse will reach it's potential fairly early so you will want to be maximising that before it's ability begins to fade. But to your question the answer is no, you can race your horse at an early age as much as you like even if it's deterioration potential is low and it will not affect when your horse peaks as that is predetermined before you start.

Thanks, am not sure I have a potential bar? I play sorders 4 jumps on my iPad so think am bit behind the newer version.