A strong Castleford team scored eight unanswered tries to race into a 48-0 lead at the break.
But the Dons could take plenty of heart from a second half which saw both sides score three converted tries.
Misi Taulapapa, Zac Braham and Tom Halliday touched down for Doncaster with Connor Robinson adding the extras.
Doncaster host Thornhill Trojans in the second round of the Betfred Challenge Cup on Sunday.
Dons: Taulapapa, Halliday, Smeaton, Storey, Corrion, Johnston, Robinson, Fella, Burns, Braham, Ollett-Hobson, York, Peterson. Interchanges: Sanderson, Whitmore, Seaman, Ruan, Roberts.
Castleford: Evalds, Olpherts, Fonua, Mamo, Faraimo, Trueman, Richardson, Lawler, Robb, Massey, Blair, Edwards, Westerman. Interchanges: Turner, Marris, Sutcliffe, Griffin, Hepi, Clare, Smith, Morley, Matagi, Vasuitoga, Martin, Hall, Brennan-Jones, Ransome, Qareqare, Sadler, Carter, Collins.
1. New boy
Dave Peterson made his first appearance for Doncaster. Photo: Andrew Roe/AHPIX LTD
4. Storey time
Robbie Storey was another debutant for the Dons. Photo: Andrew Roe/AHPIX LTD