This was an interesting point.
'Hungry cats hunt better'
Some cats are kept as mousers and their owners believe that cats become 'soft' if fed. A hungry farm-cat hunts only enough to feed itself, while one that receives food hunts for 'sport' and catches prey more frequently.
We feed the outdoor 'mousers' the same as we feed Pheobe, the indoor Persian. They still top up their diet with mice but it makes sense that most of the hunting would be just 'sport' . That's okay though, mice are already coming in from the paddocks here, I see them in the garden and I'd rather they didn't get into the house.