While it may be hard, animal nutrition could help you a lot in the future, and getting that one under your belt wold be a very good thing, as no matter what you are going for a career dealing with animals. Keeping slogging and finish this semester no matter what, okay? I know people who dropped out at a similar point, and they all regret it now, years later. After you graduate, I don't think any future employers will care much about your GPA - just that you completed the courses successfully.