When it comes to proving optimum nutrition for our pets, reputable pet food manufacturers have done the work for us. Research scientists have formulated commercial diets containing all the nutrients normal, healthy dogs or cats need for a particular life stage. Not only are high quality pet foods nutritionally balanced, they are also formulated to be highly palatable to the pet. Some foods fed in excess may cause health problems. For example, repeatedly adding raw eggs to a pet's diet may cause a deficiency of the vitamin biotin.
Egg whites contain an enzyme which destroys the vitamin biotin.
Symptoms of biotin deficiency include dermatitis, loss of hair and poor growth. Milk, if it is offered, should be in small amounts and never used as a substitute for water. Some adult dogs and cats are not capable of digesting large amounts of milk. It contains the sugar lactose, which requires the enzyme lactase for breakdown in the intestinal tract. If the intestinal tracts does not contain sufficient lactase, consumption of a high level of milk may cause diarrhea.