A pet left unfed is traditionally read as a small, dependent part of you — a hobby, a talent, a need — that has been neglected. The guilt in the dream points to what asks for daily care.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.