Yes, unfortunately it does seem that taking easier classes as opposed to the hardest classes is a benefit for most vet schools. They usually give you an objective score based on gpa/gre scores. Some schools will give you an extra point or two for being in an honors program, but in my opinion (and I've taken mostly honors classes), being an animal sciences major as opposed to an honors biology major would be a huge benefit for getting an interview. I think once at the interview stage they do look at your classes a little more, but your objective score does still play a factor. What you should really consider is the rigor of your classes will help you once in vet school. Though taking harder classes may give you a slight disadvantage in getting into a school, your are going to have an edge over those people that took the easier road.
Rosemma - If some of the psych classes you are talking about are neurobiology or psychobiology classes (I'm assuming they are from the strong science content) I'm sure the adcomms will look on that quite positively.