Age Specific Health Issues

Under 1 year 
Trauma is more likely to be life ending in juvenile dogs (up to one year of age)-23% compared to adult dogs (greater than one year of age)-10%. from here
Spay/Neuter
Vaccinations
Respiratory Issues Emerge

Under 3 years
Warts and Histiocytomas (see lumps and bumps)

1-3 years
Environmental Allergies 

2-5 years
Hypothyroidism

3- 6 years
Intervertebral Disc Disease
Food Allergies ( below 1 and after 3 years)

Senior Dogs 6 yrs +