Agricultural producers are necessary for reasons of food security but they are subject to great economic, social and environmental issues, jeopardizing their continuity. More particularly, the European dairy producers have recently experienced a big change of their economic and political context following the end of the dairy quota system. For the sustainability of the sector and what this implies for our society and our environment, it is interesting to know the development paths implemented, planned and considered by the producers facing these changes. This thesis studied these development paths from the point of view of the producers, who are the first to be impacted by these changes of context and the first actors of solutions needed to adapt and maintain a profitable activity. The actions and the opinions of the Walloon producers were studied using the technicoeconomic database of Elevéo as well as surveys conducted in 2014-2015 and 2020. The objectives of the thesis were (1) to study the strategies of the producers and the evolution of these strategies in a recent past, their planning from 2020 onwards and their consideration for an ideal future, (2) to study the link between these strategies and other information, reflecting the causes of these choices, the environmental considerations, the wishes for training and the quality of life of the producers, providing an insight of the determining factors and the sustainability of these strategies, (3) to study the relevance to adapt the management depending on the adopted strategy(ies). First, the level of intensification was measured in this thesis thanks to an index created on the basis of several variables related to feeding, coming from the technicoeconomic database. This index aims to provide a more complete and exact measure tool of intensification. Its evolution between 2007 and 2017 was measured per individual to highlight the evolution patterns. We observed that 27% of producers were having a constant evolution, 8% a linear positive tendency, 24% a ...