Selection for narrow breeding goals, such as intrinsic growth ability, may reduce the animals’ ability to cope with pathogen challenge (Rauw et al., 1998). Using mice divergently selected for body weight, it has been shown that selection for high body weight reduced ability to cope with a parasitic challenge under low dietary crude protein (CP) conditions, whilst increasing protein nutrition from 50 to 250g/kg dietary CP reduced the penalty of infection in the high body weight line (Houdijk & Bünger, 2007). However, host resistance was not sensitive to protein nutrition, which may have been due to the observed increased food intake on the low CP diet and/or a reduction of food intake as a consequence of excess protein on the high CP diet. The current experiment addressed these assumptions through assessing interactive effects of intrinsic growth ability and infection at a range of levels of dietary CP contents.