Animal well-being has both physical and psychological components. No single objective measurement exists that can be used to evaluate the health and well-being of animals. Recognition of pain or discomfort in animals is frequently more difficult than in humans and assessment can be affected by many complicating factors including animal age, nature and frequency of human contact, and control of visual, auditory, olfactory and tactile stimuli. 

Assessment should be made in relation to the prior condition of the animal and compared to what is known about the normal behavior and activity for the species and breed. Experience in observing and caring for animals is extremely important to accurate assessment of animal well-being.

General Physical Condition Symptoms of Pain Evidence of Injury
Hair loss Attraction to area of pain (licking, biting, scratching, shaking, "guarding a particular body area, etc.) Abnormal muscular coordination
Lack of appetite Restlessness/anxiety (frequent changing of position, pacing) Bruises
Low or no water consumption Abnormal respiratory sounds (grunting, etc.) Convulsions
Excessive water consumption Increased respiratory rate Dilated pupils
Abscesses Decreased skeletal muscle tone Bleeding
Blood in feces or on bedding or pen surface Limping Limping
Constipation Reluctance to move, stilted gait or hobbling Partial or complete paralysis
Diarrhea or abnormal feces Loss of appetite Wounds
Coughing or sneezing Dramatic change in behavior  
Abnormal discharge from any body orifice Subjective changes in attitude, brightness of eyes, appearance of coat, etc.  
Difficult breathing Abnormal posture  
Abnormal skin color (e.g. gums, eyelids, etc.)    
Growth retardation    
Listless appearance    
Dull or closed eyes    
Parasites visible in feces or on skin    
Rough hair coat    
Excessive salivation