A physiological condition determination system and method can include: attaching a tag to animal tissue； emitting light into the animal tissue； detecting a first optical signal； extracting a first measurement of peripheral capillary oxygen saturation from the first optical signal； qualifying the first measurement of peripheral capillary oxygen saturation as a baseline； detecting a second optical signal with the optical sensor； extracting a second measurement of peripheral capillary oxygen saturation from the second optical signal； qualifying the second measurement of peripheral capillary oxygen saturation； storing the second measurement of peripheral capillary oxygen saturation as a tag feature set； storing a history； determining animal distress based on the difference between the second measurement of peripheral capillary oxygen saturation and the baseline； and sending an instruction to the tag.
