S.D. Codified Laws § 40-27-3
In the event animals subject to a lien under § 40-27-1 shall be mortgaged, the person to whom entrusted may serve notice in writing on the mortgagee to the effect that he is feeding, herding, pasturing, or ranging said animals, or is about to do so. Such notice shall describe the animals generally and give the name and address of the person entrusting the same and the date when the service commenced or a future date when it is to commence, and the probable amount of the charge for such service and supplies. The notice may be served personally upon the mortgagee or by sending the same by registered or certified mail to said mortgagee at his post office address as set out in the mortgage. Upon service of such notice any charges for service or supplies subsequently accruing pursuant to the notice shall be a prior lien to said mortgage to the extent only of the value of said service and supplies.
SDCL 40-27-3