how many litters can a dog have before the dogs begin to come out weak,thanks
also do dogs sperm run out,thanks

Sperm don't run they swim :D (sorry, couldn't resist)

Im not really qualified to give an answer to that, nor would I.

Honestly, why do you really need to know?

It is a case of how long is a piece of string.  A dog should be capable of siring puppies for as long as he is able to mate a bitch, though fertility can decline or cease with some males, usually due to some health issue.

If the sperm are capable of fertilizing an egg they should be able to produce pups of the same potential health throughout the dogs life. 

Of course it also depends on the genes of the mother and which negative ones they both carry, and how these combine in the offspring.

As for the vigour of the actual pups that is primarily dependant on the mother, how well they fared in the womb and afterwards.

i would never let my dog have any more than 2-3 litters in her life , well spaced out, year or two between each one.
please dont use your dog for just breeding, your dog will suffer as will the quality of the puppies produced.  too many puppy farms out their makes me sick

I think the OP is talking about a dog not a bitch :)

I thought that the OP was asking about both!  I breed mine 3 times in their lifetime.  My males, well I'm not sure.  Have used an 11 year old and had pups from that but I was really worried about him as it was a 30 minute tie.  My latest boy is 8 in May but he's still really fit so think he'll be used for a while yet.

i agree with brainless males can continue for as long as they can mate a bitch but their sperm count generally declines. As for girls i breed 3 litters not one after the other and then i retire my girl to live a life of lounge snoozing. I know my girl could have more than three but i believe after a certain age your playing with fire and i dont start breeding until they are 3 making her last litter at 6. But that is just my opinion some people believe it makes no difference if they are 6 or 8 so it is really a decision that is made with consideration to the type of breed you have and on your own girl and your own beliefs.

Hi,
The age of breeding, "from and two" can depend on how long between there seasons,
As it is bad practice to breed on one season then the next. There is More chance of problems
with your bitches health also the puppies.
Regards
Denese