The age at which a male dog reaches sexual maturity and begins to produce sperm varies from 6 to 12 months, the average being about 9 months. Physiologically, a male could be used at stud at about 1 year of age. Most male dogs, however, do not achieve physical maturity before 18 to 24 months of age, and should not be used before that time. This is because their full breeding potential does not become apparent until they reach physical maturity. Also, many health certifications, such as OFA clearance for hip dysplasia, require the dog to be at least 2 years of age.
A stud dog should be kept at an ideal weight with regular exercise and a sound diet. Exercise maintains physical condition, endurance, and muscle tone. Regular health checkups are important. Vaccinations must be kept current, as the stud will have close contact with a number of bitches (see Vaccination Schedule).
The Prebreeding Examination
Before a male is used at stud he should undergo a complete physical examination with laboratory tests similar to those described for the brood bitch. Parasites, if present, should be treated. Heartworm preventives are important in areas where the disease is known to occur. Screening tests for von Willebrand’s disease and hypothyroidism may be necessary for certain breeds.
It is extremely important that all prospective stud dogs undergo screening and certification for hereditary orthopedic and eye diseases, as well as other genetic disorders for which they may be at risk. Dogs with any of these diseases should not be used at stud.
All prospective stud dogs should have a brucellosis test. Repeat the test every 6 to 12 months, depending on how active the dog is at stud. Once introduced into a kennel, brucellosis can cause widespread sterility and ruin a breeding program.
The reproductive tract examination includes an inspection of the penis, the prepuce, and the testicles, and digital rectal examination of the prostate. A semen analysis is not necessary unless there is some reason to suspect infertility, but should be done on a young male and on older males to be sure they are fertile. Some breed registries require this on male dogs over or under a certain age to be sure the male is fertile.
Inspection of the penis may reveal a sheath infection, phimosis, or paraphimosis. A retained fold of skin (called frenulum) may prevent protrusion of the penis. This can be treated by your veterinarian. Some males have a long, flexible forepart to the penis that can bend backward and make intromission difficult or impossible without assisted breeding.
Solitary or multiple ulcerated cauliflowerlike growths up to an inch in size that appear on the shaft of the penis may be transmissible venereal tumors. They will not be found on virgin dogs, because they occur as a consequence of breeding. All growths on the penis should receive veterinary attention. Lacerations and erosions tend to bleed when the penis is erect. If blood gets into the ejaculate, it can reduce the motility of the sperm.
Both testicles should be present in the scrotum. They should be of similar size and have a rather firm consistency. A dog with two undescended testicles is sterile. A dog with one undescended testicle may still be fertile, but should not be used at stud because the condition is heritable.