hi i have a 12 month old bullmastiff stud dog he has sired 4 litters only they have been very small in this order 1.3.1.2 all the bitchs have had big litters befor from our other stud but I would like to know if  I should  use this stud again will he get better with age

12 months old and sired 4 litters?   At what age did you carry out all the necessary health checks before using him at stud?

Margot

Take him to a reproduction / fertility specialist vet & get him fertility tested. It's a simple procedure & will tell you how good his fertlilty is  :)

If he is only 12 months old then you shouldn't have used him yet as he won't have been old enough to have his Hips scored until 12 months and the results often take up to 6 weeks to come back.

If he has already been used foru times what age was he first time.  such a big breed will be less mature than a smaller one at that age.  How far apart where the matings?

Our imorted boy was used for the first time at 14 months then a couple of monts later so had sired 3 litters in the first year then 3 litters in his second.  Hoping for  a first litter from him this year in July, and he has two other bitches booked. 

Sounds like he has been used too often too young, and without health tests to boot is most irresponsible.