The invention concerns a method of sustainably producing an pet food productorproduct, said method comprising the step of formulating a pet food product byreplacing all or part of fish oil in the composition with a single microbialsource ofeicosapentaenoic acid ("EPA") and docosahexaenoic acid ("DHA"). In a preferredembodiment, the microbial source comprising DHA and EPA derives from amicroorganism/microbe of the genus Schizochytrium or Thraustochytrium.