I went to an abattoir for a day before I applied, and yes it was horrible but it was also interesting. I know I would never, never want to have a job there or anything, but at least now I know what happens. Also I got asked about the role of a vet in an abattoir at my edinburgh interview, so I explained about checking animals for cleanliness before slaughter, checking carcusses etc etc. They then asked me if that type of career path would appeal to me. There was no point lying so I told them outright that at the moment it definately does not appeal to me, and although I found the experience interesting and am glad I decided to do it and that I understand the importance of a vet's role in the prevention of disease and in culling animals in a humane way that I definately want to work as a clinical veterinary surgeon. They didnt mind this at all - I still got an offer! Instead they just asked me what type of vet work I would prefer to do, whether I would like to specialise etc. So dont worry, dont think you have to pretend that you enjoyed it.
Oh, and I have a really good sense of smell and yes it is disgusting! I just had to force myself to breathe through my mouth for 5 hours.