As veterinary efforts reduced outbreaks of rinderpest in the Gambia, the colonial government sought to capitalize on an increased rural cattle population. One idea was to build a boat—the Jarga—to ship cattle downriver to the capital. This article recounts that venture. Whereas attaining knowledge of livestock disease ecology in the region was rather conducive to British expertise, livestock marketing proved otherwise. Farmers' practices may have, at times, informed colonial agricultural practice in Africa, but this repositioning of authority did not extend to matters of local economics. Ultimately, a refusal to defer to local relations of exchange spoiled the colonial effort at livestock development in the Gambia.