Subvalvular aortic stenosis (SAS)
Subvalvular pulmonic stenosis
Sudden acquired retinal degeneration (SARD)
Summer pasture associated obstructive pulmonary disease (SPAOPD)
Sunshine virus infection
Superficial digital flexor tendinitis
Superficial digital flexor tendon (SDFT) luxation
Superficial digital flexor tenosynovitis (tenovaginitis)
Subsolar abscessation
Systemic lupus erythematosus (SLE)