Wales 18 South Africa 43
Wales finished their U20 IRb Junior World Championship campaign in the same position as last year's tournament in Belfast - 4th position. Horgan's men were comprehensively beaten by South Africa who ran in seven tries at the Liberty Stadium.
The dragons did breach the Springboks defence twice through Leigh Halfpenny and Sam Hobbs but it was too little, too late as South Africa galloped into a 26-6 interval lead.
Wales end the year with a 70% success rate having only lost to the top three in this tournament - England in the U20 Six Nations and New Zealand and the Springboks in this competition.
The hosts began brightly through Halfpenny's fourth minute penalty before South Africa showed clinical finishing with the first try of the match from Francois Brummer - the tournament's leading points scorer.
South Africa extended their lead in the 19th minute as centre Robert Ebersohn stormed through the Welsh defence for the second try. Halfpenny reduced the arrears with a 24th minute penalty but a break from Robert Ebersohn five minutes from half time brought a third try for South Africa.
But they weren't finished there and to cap a fantastic opening half, flanker Koster nipped in for the fourth try after a flat pass from Robert Ebersohn. Brummer converted for a 26-6 interval lead and Wales's main objective was to stem the tide.
Wales refused to give up and Halfpenny took Gareth Owen's pass to cross for the home side's first try on 54 minutes. Then Sam Hobbs crashed over following a driven line-out which Halfpenny converted.
But South Africa hit back through tries from replacement Frederick Kirsten, Lionel Mapoe and fly half Josias Ebersohn in injury time.
Wales: Jason Tovey (Dragons); Leigh Halfpenny (Blues), Jonathan Davies (Scarlets), Rhys Williams (Scarlets), Nathan Rees (Blues); Gareth Owen (Ospreys), Gareth Williams (Ospreys); Ryan Bevington (Ospreys), Ryan Prosser (Bristol), Scott Andrews (Blues), Haydn Pugh (Scarlets), Ashley Sweet (Dragons), Josh Turnbull (capt, Scarlets), Justin Tipuric (Ospreys), Lloyd Phillips (Scarlets)
Replacements: Ben Roberts (Dragons), Sam Hobbs (Blues), Pat Palmer (Blues), Jake Thomas (Blues), Rhys Webb (Ospreys), Dan Biggar (Ospreys), Daniel Evans (Scarlets).
South Africa: Wilton Pietersen; Cecil Afrika, Robert Ebersohn, Francois Brummer, Lionel Mapoe; Sias Ebersohn, Francois Hougaard; Jean-Jacques Rossouw, Henri Bantjes, Wiehahn Herbst, Martin Muller, Cornell Hess, Nick Koster, Thiliphaut Marole, Gerrit Jan van Velze (Capt)
Replacements: PJ van Vuuren, Frederick Kirsten, Corne Fourie, Sabelo Nhlapo, Johan van Deventer, Dewaldt Duvenhage, Vainon Willis.
Referee: Romain Poite (France)