Factors correlated with the presence of rodents in outdoor pig farms in Denmark and suggestions for management strategies

Summary

The correlation between farm characteristics and the occurrence and importance of rodent pests on outdoor pig farms in Denmark was explored in an extensive questionnaire survey. Mice occurred on most farms but were only rarely considered a problem, as opposed to rats, which were controlled on more than half of the farms. A series of trapping studies showed a high small-mammal diversity in and around the pigsties. The presence of rats was positively correlated with farm size, the presence of straw stacks near the pigsties and the use of automatic feeders. Rats were considered a problem more often when open drinking basins were used or when feed was stored near the pigsties. The environment of the farm did not play an important role except to some extent the proximity of hedges. Recommendations for preventative rodent management include avoiding these conditions, frequent mucking out and movement of huts, keeping feed in rodent-proof containers, avoid spillage of fodder, and general cleanliness. Direct control methods include application of rodenticides with proper consideration for the risk of unintended poisoning of production animals, the use of traps, keeping dogs or cats, and possibly shooting.