Consumption Pattern of Bromadiolone in Presence of Alternative Food by House Mice (Mus musculus) Infesting Poultry Farms

Poultry farms in Central Argentina are often infested by Mus musculus L., despite the regular application of the rodenticide bromadiolone. This failure may be explained by the consumption pattern of mice, which may prefer alternative foods available on the farms to bromadiolone baits. Here we examine the consumption pattern of bromadiolone in the presence of wheat by M. musculus infesting poultry farms compared with the laboratory CF1 mouse strain. Overall, the poultry farm mice had longer survival and lower total food consumption in comparison with the CF1 mice. On the first day of the experiment, rodents from both strains and sexes consumed bromadiolone in the same proportion as wheat. On the second day, female mice of both origins showed a significant decrease in the consumption of bromadiolone, while males kept that proportion constant. Despite the consumption differences between males and females, survival rates were not different. We concluded that rodents from farms behaved as if they had never been in contact with bromadiolone, since they showed the same pattern of poison consumption that the CF1 mice. Females may have associated physical upset with the consumption of bromadiolone, since they decreased its consumption relative to wheat. However, this consumption pattern did not help them to achieve higher survival than males. On poultry farms, the balanced food fed to chickens may function as an alternative food to the poison for rodents. Therefore, we propose that rodenticide should be applied during downtime, when shed are cleaned and there is no chicken feed, which could be used as alternative food.