Siberian Husky not conceiving

Question
Hi Renee,
I hope you can give me some kind of insight here.  I have a 4 year old Siberian Husky. I found the perfect stud for her after a long time of looking, so we attempted a breeding back in January on day 9 of her cycle.  They tied perfectly on that breeding.  I took my female back on day 11 and she was in obvious standing heat, but the male would not breed with her.  I kept taking her back, every other day, while she exhibited standing heat, and he still would not tie with her.  He would mount, sniff, lick, but would not do the actual "duty."  She did not get pregnant.  My vet recommended waiting until a later day of her cycle to breed the next time around.  The stud's owner granted a breed back, so I took her on her next cycle. She was bred  with perfect ties on Oct 1 (day 14), Oct 3 (day 16) and Oct 5 (day 18), and she showed perfect standing heat and was very receptive all 3 times. By day 20, she was definitely out of receptive heat.
I took her for an ultrasound on Oct 24, and the vet said the ultrasound was inconclusive, that she could see a few "suspicious" spots, but she wasn't ready to say it was a pregnancy and asked I bring my female back in a week.  Well, we just got back from the 2nd ultrasound(Oct. 31st) and the vet said my female is not pregnant.
The male has sired 3 or 4 litters that I'm aware of. I know one litter was of 3 pups, another was only 1 pup and another was 7 pups.  I do know that he did breed another female that also did not get pregnant, but I was told that the female's owner stated that she has had problems conceiving in the past.
My vet seems to believe that there could be a problem with the male's sperm, or we are just not getting the timing of the breeding right.
We discussed my options at this point and I'm just wondering which would be the better route... take my female in for testing, beginning on day 6 of her cycle to determine ovulation and do another natural cover, or doing AI, where my vet said they would add an extender and some kind of a "booster" to the male's semen to insure that it is living long enough.
My concern is that I'm running out of time with my girl. She will be 4 yrs. in December and her cycles are usually every 7-8 months.
So I guess my question is... which option do you think would be the best route for me on my girl's next cycle?  
Thank you in advance for your help.

Answer
Hi Sandy. I still wouldn't loose hope this heat. Going by the first bred date, that would put her at just 31 days. Going by the last date bred, she would have just been about 26 days. It's still pretty early, and sometimes even ultrasound won't pick them up this early. Is she showing any pregnancy signs at all?

If she didn't take this time, I would have her checked for an infection. Even a low grade one can mess up her conceiving. Then, I would definitely use progesterone testing to help you figure out exactly when this girl is going to ovulate. It really is a helpful tool, especially if you're going to use A.I. If you're truly worried about timing, I'd go ahead and use A.I. You may want to also have your vet have a look at the sperm before inserting, just to make sure that everything's ok with the male. Has he been checked for any infections? Has his thyroid been checked? This is what I would do if this were my girl. You still have some time left to figure this out. Again, I still wouldn't lose all hope this heat cycle, she may have a surprise for you yet.:-)