Boxer Heat Cycles

Question
My 6 year old Boxer was bred once at 5 years of age and produced a healthy litter of 7. It's now been 15 months and counting since her last heat. All of the literature I've read indicate heats can vary greatly depending upon the bitch. She's perfectly normal and healthy in every aspect, but at what point should I get concerned? I've only owned her 2 years and the previous owner can't tell me much about her past heat cycles. Also, what's a good age to retire? She's a very young, spry 6 year old and has only had one litter. I was hoping to have 1-2 more litters from her and retire her at about 8 given her health and energy maintains. Thanks

Answer
Yes, heat cycles can vary, but 15 months between seasons would be considered unusual in any case.  She may have had a 'silent heat' at some point - where there is little swelling or blood.  However, if it were my bitch I would probably schedule an appointment with my repro vet just to make sure there's nothing else going on.

As far as retiring her, there are different opinions and the health and condition of the bitch is of course the largest concern.  The American Boxer Club Code of Ethics states that bitches may not be bred past six years of age - with an average lifespan of nine to eleven years, Boxers are considered "senior citizens" at seven.  If you want to breed her in her senior years, again I'd suggest a consultation with a reproductive vet - and a surgical implantation breeding might be something to consider, because the vet can take a look at the uterus to see what kind of shape it's in.  (A bitch's uterus is damaged to some degree every time she goes through a heat cycle, whether or not she carries a litter; in some older bitches, even those who have never been bred, the uterus can be thin-walled, or prone to 'bubbling', both of which increase the chances of pregnancy complications and pyometra.)