A network of 42 sheep farms (including 13 in organic farming (OF)) shows that the gross margin per ewe is 24% lower in OF in the mountains because of high food costs and comparable in the lowlands because of the high level of food self-sufficiency based on the cultivation of fodder and grain; incomes are identical when structural costs are comparable. An analysis of four demonstration farms shows that, given the different conditions, specific livestock management is required depending on the presence of tillable land or not. If their proportion is limited, lambings are equally distributed between spring and autumn in order to maximise fodder self-sufficiency. When crops are possible, lambings are focused on autumn (with good sale prices), which requires the increased use of concentrates, some of which are produced on the farm. A five-year study revealed that these strategies lead to a convergence of between 80 and 90% food self-sufficiency. In suckling livestock in organic as well as conventional farming systems, high levels of forage and food self-sufficiency are essential to ensure economic viability within the context of rising grain prices.