Abstract: Provided are a livestock sensor device, a livestock astasia inference method, a livestock astasia inference program, and a livestock management system that are capable of preventing damage to stockbreeders. According to an embodiment of the present technology, there is provided a livestock sensor device including a postural-state determination unit, a state inference unit, a transmission unit, and a casing. The postural-state determination unit determines in which of a prostrate state and a non-prostrate state a livestock animal has been on a basis of output values from an acceleration sensor. The state inference unit infers whether or not the livestock animal has developed astasia on a basis of a duration of the prostrate state. The transmission unit transmits, to a server, an astasia-notification data item indicating that an inference that the livestock animal has developed the astasia is made when the inference that the livestock animal has developed the astasia is made.