A zebra
calf (baby antelope)
Buffalo is not really an antelope, but it is the closest relative to the antelope where the name ends with an o.
Ted
gnu
dik dik
Ibex?
Eland is an antelope
Oribi is a small African antelope
eland
kudu
Perhaps.............gnu?
A three letter African antelope is the "gnu", which ends in a "u" not a "you". The more common name for the gnu is the wildebeeste, but that won't fit into your crossword puzzle.