Raising Orphan Kittens
Orphaned kittens must be fed a commercial milk replacer specifically designed for kittens, not cow's milk

The energy requirement for kittens in the first few weeks of life is approximately 20 kcal ME/100 g (3.5oz) body weight/day.  The water requirement is 18 mL/g (3.5 oz) per day.
This equals 1 cc./ml. per ounce of body weight per feeding. 

Vigorous orphans with a good suck reflex may be bottle-fed while on their stomach with the head elevated, simulating a normal nursing position. They should be fed every 2 to 4 hours during the first week of life, and less frequently thereafter. 

Initially, only 50% of the normal amount of milk replacer should be fed to avoid inducing diarrhea. 
Extra water or an oral electrolyte solution can be added to  make up volume and provide fluid needs. 
Over several  feedings, the concentration of the formula can be  increased to that recommended by the manufacturer.

Reconstituted milk replacer should be warmed to 35-  38 degrees C (95-100oF) by immersing the container in a warm  water bath.  Never microwave formula as overheating  may result. 

Avoid overfeeding; the maximum stomach capacity for  kittens is about 4 mL/100 g (3.5 oz) body weight.

Avoiding Problems
Diarrhea is  the most common problem seen in kittens fed milk  replacer.  It can be treated by temporarily reducing the  amount fed and by diluting the formula by 50% with  water or electrolyte solution (Pediolyte) for a few feedings.

 Orphan  kittens should be weighed every 12 hours to ensure  nutrition is adequate to support maintain weight and allow for growth.

 Orphans under  3 weeks of age must have the anogenital area stimulated  after every feeding to induce defecation and urination. 

At 3 to 4 weeks of life, kitten food can be introduced by mixing a small amount of food with formula and offering  it in a saucer.  Once the kitten has learned to eat from a  saucer, the amount of formula fed can be slowly decreased  until only solid food is being ingested. 

Weaning is usually  completed by 6 to 8 weeks of age.