The Collaborative International Dictionary of English v.0.48:

Fosterage \Fos"ter*age\ (?; 48), n.
   The care of a foster child; the charge of nursing. --Sir W.
   Raleigh.
   [1913 Webster]

WordNet (r) 3.0 (2006):

fosterage
    n 1: encouragement; aiding the development of something [syn:
         fostering, fosterage]
    2: helping someone grow up to be an accepted member of the
       community; "they debated whether nature or nurture was more
       important" [syn: breeding, bringing up, fostering,
       fosterage, nurture, raising, rearing, upbringing]

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "fosterage":
   abetment, advocacy, aegis, auspices, backing, care, championship,
   charity, countenance, encouragement, favor, goodwill, guidance,
   interest, patronage, seconding, sponsorship, sympathy, tutelage