The rhizomatous alfalfas are appreciated for their tolerance to drought and rambling which makes them very interesting for grazing in semi-arid regions. A 'mielga' population from Spain, characterised by a rhizomaous habit, was compared in this study with the hay-type cultivar Aragón under a 15 days-frequence defoliation regime. Top-growth protein content and crown diameter were analysed. The mielga population showed an appreciable and stable protein content across the cuts, although lower on average than that of Aragón. On the contrary crown diameter was larger in the mielga than in the hay-type cultivar.