The influence of feed evaluation system and type of forage in the rations for three, eight and twelve months old goats optimized through minimum cost linear programming was studied. The rations included one of three forages (lucerne hay, oat hay or cereal straw). The energy and protein supply and requirements were derived according to NRC (2007) or INRA (2007). The calculated energy intake and the cost of the rations were different between the systems, whereas there were no differences in the calculated intake of protein, forage and concentrate. Cereal straw and oat hay rations were the most cost-effective (P<0.05) regardless of the age group or the system used. It was concluded that the choice between NRC (2007) and INRA (2007) to formulate rations for young growing dairy goats through minimum cost linear programming is not relevant from both nutritional and economic points of view. Oat hay and cereal straw could be valid substitutes for lucerne hay as roughage source when designing rations for young growing dairy goats.