abstract: Freemartinism is a biological phenomenon in genetically female cows born from a dizygotic twin pregnancy. Placental connections—blood and hormones between the freemartin and their male twin—generate an intersex cow unable to conceive. In this study, the freemartin emerges in a constant state of flux: between waste and use; becoming a technology and supplemented by other technologies; defined by human anxieties about gender; and a tool underscoring dominant gendered ideas about normative family life, human sex, and sexuality. It examines farmers and scientists' numerous attempts to harness the indeterminacy of the freemartin's liminal sex characteristics, and how dairy farmers transformed the freemartin into a heat detection technology, thus maximizing other cows' reproductive performance. Unabated scientific and agricultural engagement with freemartins has inspired new ways of thinking about the biological self and nonprocreative sexual pleasure on industrial farms.