The phrase "to affect the pup" means to have an influence or impact on a young dog. It suggests that something is causing a change in behavior, mood, or health of the puppy. Full definition
In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers is not recommended. (pawprintgenetics.com)
Even so, we have found carriers and affected pups in kennels from coast to coast and north to south due to the widespread sharing of breeding stock. (thedogplace.org)
The pain of the swollen tummy makes affected pups act restless within just a few hours of eating. (thesprucepets.com)