For some fifteen years, dairy cattle farming has been considerably developing in various parts of the Andes. Milk is transformed into cheese or sold fresh, giving rural families a regular income which secures their food supply. The stock-rearing practices in these Andean dairying systems are unrecognized and are often considered, wrongly, as underperforming and inadequate. Eight families, belonging to a rural community in the dry parts of the Peruvian Andes (in Sinto), were monitored during a whole season; the analysis of their stock-rearing practices constituted the basis of this paper’s assessment of the forage management in use in these dairy farms subject to severe constraints. The allotment of cattle heads, the rotational grazing of irrigated lucerne pastures by the cows in milk, the availability of huge rangelands, and the swapping of foggage make it possible for the Sinto farmers to produce milk all the year round, in spite of their very dry climate. The amount of milk produced in each family and its regularity during the year depend narrowly however on the area of irrigated land to which they have access. The low milk performances per cow are no obstacle to a good output per hectare of lucerne, which corresponds to both an optimal use of the main limiting factor and to a good risk management.