Go to a semen collection facility,one that preferably works with performance dogs(my one specializes in greyhounds).. and ask them if they can check your dogs semen..(they will tell you how good the semen is and if its good enough to freeze)..you may have to ring and book an appointment,and also get a price..

now,if the dogs semen is no good...they may have some supplements that can help boost sperm count....
if not..I use to use some horney goat weed and tribulus...worked fine for me!!