well they interview the top 500-600 scorers on their work experience form. so the issue would be having enough to actually get an interview rather than getting in. once you've got an interview it's pretty much how you do in that, and nothing to do with your work experience after that point.
cover the basics really and you shouldn't have a problem: cattery or kennels...or both, farm work dairy and lambing if possible, definitely at least a week horses, and minimum of 4 weeks total in a vets practice; both large and small.
then try and get some of the extra stuff that will make you stand out if you can get it/have time. a day at an abattoir, some time in a vet lab or a zoo are some good examples.