Supplement material for use in pet food

The invention concerns a method of sustainably producing an pet food product or product, said method comprising the step of formulating a pet food product by replacing all or part of fish oil in the composition with a single microbial source of eicosapentaenoic acid ("EPA") and docosahexaenoic acid ("DHA"). In a preferred embodiment, the microbial source comprising DHA and EPA derives from a microorganism/microbe of the genus Schizochytrium or Thraustochytrium.