your best bet for finding out what work experience is definitely needed for your course is to call up and actually talk to someone as previous posters have suggested.
When I applied last year I had done 2 weeks in an equine practice, 2 weeks in a mixed practice plus I have a strong equine background and have worked in stables. From what I remember, this was enough for most and anywhere that wanted more experience would allow the summer/until term started to get the rest of the experience.
From interviews etc it seemed everyone applying had a range of experiences... from working in practices and rescue centres to just a couple of weeks.
Try and get as much experience as possible, even if its not required for your course because it will really stand to you down the line (those who have the least hands on experience on my course do really find it hard). Try and get experience with all sorts of animals, especially if the course you want to do isn't specifically SA/LA/equine etc... not just the animals you're used to and most interested in. For example, if you're a small animal person, do really try and get experience with horses and farm animals.