Is the preservation of biodiversity a matter for specialists alone? Can the practical knowledge of those involved in preservation contribute to the conception of desired changes, and if so how? This article presents a case study of the protection of the Maraîchine cow, a breed limited in number living in the marshlands of the French Atlantic coastal region. The following analytical point of view is adopted: the breed is a biological object mediating different forms of knowledge, that is, it is a vector of learning for different actors. It plays this role because those involved with it are placed in a situation of dialogue with respect to its preservation and in a concrete situation as breeders, which leads them to modify how they represent a “suitable animal”. The hardy Maraîchine, adapted to extensive breeding, is leading farmers to move gradually away from the intensive production that has been their reference point. The breed enables them to reconsider the relations between their activity, the marshland areas, and the preservation of nature. It leads farmers to reconstruct links among themselves and with the world of consumers. In this sense, the Maraîchine is the basis on which breeders in wetland areas have re-established an individual and collective identity.