Many evacuated livestock have fortunately returned home.

If you’re caring for livestock that were exposed to days of wildfire smoke, keep them quiet. That is, limit exertion, even for several weeks after the air quality has improved. Be extra sure to keep fresh water always available. For more information, see https://extension.oregonstate.edu/animals-livestock/beef/animal-exposure-wildfire-smoke.
See also https://www.oregon.gov/oda/shared/Documents/Publications/AnimalHealth/CaringforLivestockAfterWildfire.pdf

If you lost hay or pasture in the wildfires or are feeding displaced animals that don’t belong to you, OSU Ag Extension is coordinating a statewide hay donation and distribution program to those in need over the next 3 months.  Three regional locations are being set up for receiving hay donations and distribution, in Aurora, Roseburg, and Central Point.  If you need hay due to wildfire loss or to housing extra, unexpected mouths to feed, please fill out this form: https://oregonstate.qualtrics.com/jfe/form/SV_b8BCqXt7sgbM113

Some livestock have not returned home.

For livestock that may have gone missing, Oregon Department of Agriculture has established an animal tracking website with a database of “found” animals and a way to submit information on animals with unknown owners that you may be tending. https://data.oda.state.or.us/fmi/webd/AH_AnimalTrack?homeurl=https://data.oda.state.or.us/ah.html

For those with livestock that perished in the wildfires, there is the Livestock Indemnity Program (LIP) from USDA Farm Service Agency. General information about the program can be found here: https://www.fsa.usda.gov/programs-and-services/disaster-assistance-program/livestock-indemnity/index
An Oregon wildfire-specific fact sheet on the LIP is here: