I'd highly recommend Pixologic's free program Sculptris available for Windows and OSX. It'll import your OBJ file. Once in the program, use the masking process to lock down parts you don't want to move and apply rotation to bend unmasked areas:

http://www.zbrushcentral.com/showthr...y-first-sculpt

My dragon sculpt from that page started with the creature sculpted straight like a yardstick. Using the masking, it was eventually bent into a ring shape and printed.

There's a fair number of Youtube tutorials for Sculptris floating around:
https://youtu.be/4fpxfQUD3Uo

Might be useful to study some reference photos so that you can move the calf's features around.... just like how infants aren't merely proportional scaled versions of full-grown adults. While in the program, use the opportunity to smooth out (remove) any barnacles and extra bumps that might be on the adult version.

If installing the OSX version, just search the forum sticky post about making a small config-file change to fix a display issue.