[Object] To provide a livestock management system, a sensor apparatus, and an estimation method for a state of a livestock animal with which states of livestock animals can be easily and accurately estimated. [Solving Means] A livestock management system according to an embodiment of the present technology includes a management apparatus. The management apparatus includes a reception unit that receives power generation information from a sensor apparatus configured to be attachable to a livestock animal and including a power generation unit that generates electric power in a manner that depends on a surrounding environment and a transmission unit that transmits the power generation information of the power generation unit with electric power obtained by the power generation unit, and a control unit that estimates a state of the livestock animal on the basis of the power generation information.
