nilgai
The antelope you are referring to is the "sitatunga." However, it does not end with a "d." If you meant to ask for an antelope with a name ending in "d," the "addax" fits the criteria but is not spiral-horned. Unfortunately, there isn’t a commonly known spiral-horned antelope that ends with the letter "d."
That would be the Impala.
Oribi
Tsessebe (Damaliscus lunatus). East African antelope ending with opi, would be the Topi.
Springbok or steenbok. Also gemsbok, a local name for an oryx in southern Africa.
calf (baby antelope)
Nyala is an antelope species in Africa. It begins with the letter N.
dikdik
Topi or Tsessebe Tibetan antelope
Addax is an antelope species in Africa. It begins with the letter a.
impala
Impala