I don't know what's going on, but I just stumbled upon my younger kitty pooping and there was A lot of blood in his poo... what could be wrong? Could it be because he ate a bit of dog food??

It's probably parasites.Take a sample to your vet to have a fecal run,and if there are parasites the vet tech can advise you what type treatment you will need.There are several different types of parasites,and some cannot be treated with over the counter dewormer.coccidia has to be treated with albon,and you can only purchase this from a vet.

I'm sorry to say this but, my dog died of cancer and had blood in his poop before he died, I advice to get to the vet QUICK!

Hope your cat gets better.

I dont know what's going on, but I just stumbled apon my younger kitty pooping and there was ALOT of blood in his poo...... what could be wrong?? Could it be because he ate a bit of dog food????
No!
You need to see the vet ASAP! There could be internal problem, not food related (actually that's about the only reason).
It won't go away by itself. You want to save the cat- take him to the vet.
Good luck