Water intake, efficiency and consumption of 30 growing individually fed Blackhead Persian, Dorper and South African Mutton Merino (Mutton Merino) ewe lambs were investigated. Average daily water intakes were 2.2, 4.6 and 5.4 litre for the Blackhead Persian, Dorper and Mutton Merino, respectively. The Blackhead Persian was 53% and 77% more efficient (water intake/kg weight gain) than the Dorper and Mutton Merino, respectively. By means of the allometric-autoregressive model, efficiency was separated into three distinctive phases. The Blackhead Persian furthermore consumed only 1.81 litre/kg feed compared to the 2.56 and 3.05 litre/kg feed of the Dorper and Mutton Merino, respectively.