dogs heat cycle/breeding

Question
myfemale rottweiler is 5yrs old she had 2 litters just went threw a false pregnancy 6months ago shes in heat now last she was put with the male not sure if there was a tie i noticed blood on sept 7th blood test on the 12th results she was a 4.5 my vet said she was ready she now wont except the older male he doesnt seem intereasted any more to should be like her 10th day of her heat i have a 2yr old male thatis all over her but she wont allow him to mount her very aggresive pining him down growling all ths with a muzzle on is she out of she seems to be ok with my other dogs inculding the older male which she has had litters with my vet wants to do another hormone test wednesdsy

Answer
Hi Dexter

If the older male is experienced, he'll know when she's ovulating.  Younger, inexperienced males tend to want to to it from the start of the heat until after their done.

Typically optimal time is when she reaches 16.  6.5 to 9 you can start so you may have some time yet.

Good luck.