Advice on killing mice

I didn't come up with but I can promise it works. My mom used to have a farm with a barn and horses. Mice love horse feed and we tried everything to get the mice but nothing was effective. One day a vet came out to the barn because one of the horses was sick and he told us about it. Well at the time I was about 12 and my younger brother was 10 and this interested us greatly. We sat up 4 buckets and went through half a thing of peanut butter and checked them every couple of minutes and nothing. Well the next day we walked down to the barn and there were several mice in every one of the buckets. The bucket that was in the feed room had 7.