"Squirrel factor"

Is there any possibility the "squirrels" that "bob" produced could have been due to the bitch's side of the equation? I have seen people breed to a stud dog and get a whole litter of culls and then say it has to be the male dog, when in reality it is the female that is the problem. Some people refuse to admit that their dog just can't produce. They may hunt but just can't produce pups that are worth keeping. One example of this is a breeding I made about 6 years ago with my APBTs. I bred a female off of my yard to this ch male and a good friend of mine bred his female to the same male about 4 months prior to me making my breeding. He had 7 pups out of his breeding and I raised 5. With his pups being older than mine he got the chance to cull or keep his first. He ended up culling all but one of his and that had me worried about how my litter would turn out. When it came time to start culling my I figured I would have to cull most of mine as well. Out of the 5 of mine I only culled one of them. When we started really looking at past breedings with his female we noticed that there was a high percentage of culls in every one of her litters. It went unnoticed because the ones that she produced that weren't culls were very good dogs. If I wouldn't have already made the breeding with my female I probably would not have because I would have assumed it was the male that was not producing. I have since bred 2 other females to the same male and have had good results out of both of them as well. The same friend bred the littermate sister of the one that produced all of the culls to the same male and that particular breeding produced 2 ch and 1 gr ch out of a litter of four. The fourth one was never shown and has just been a pet since it was weaned.