The possible use of sorghum hay in the production of milk by high and low yielding Friesland cows and firstcalf heifers was investigated and its influence on milk composition was determined. The animals were divided into four production groups, and 12 lactating cows and 12 first calf heifers were subjected to a trial having an extra period Latin Square rotating changeover design. Three complete rations with varying sorghum hay (S) to concentrate (Cl ratios were fed, viz. 20S : 8OC, 40S : 60C and 6 0S: 4OC. Whereas a higher milk production was obtained by decreasing the ratio of sorghum hay to concentrate from 60S : 40C to 40S : 6OC, similar improvement could not be obtained by decreasing the ratio further to 20S : 8OC. An overprovision of metabolisable energy (ME) from the 20S : 80C and 40S : 60C ratios was aggravated by decreased production. Viewed from an ME intake and production point of view, the 20S : 80C ration cannot be recommended for high and low yielding cows and first calf heifers.