I think your best chances of curbing any male marking would be to have him fixed and not mate him. Is she in heat now, if not, delaying the procedure increases the odds that he will still mark (the older, the greater the chance). Does your sister know that a 4 pounder may have to have an expensive C-section and all the normal costs involved with a litter, not even mentioning the risk of losing the mom in the process.
A male is most likely fertile at 6 months, if he can figure out what to do. Hope your sister won't be mad, but I would decline and let her find another stud dog. |