Sales to consumers of pets (including pot bellied pigs) and pet food are subject to retail sales tax. 
 
Sales of livestock (including swine) for breeding purposes where the animals are registered in a nationally recognized breed association are exempt from retail sales and use taxes.  Also feed to be consumed by livestock at a public livestock market is exempt from retail sales and use taxes.
 
If you have any additional questions, please write again.
 
State of Washington
DEPARTMENT OF REVENUE
December 7, 2005