Small ruminant studies have shown that a reduction in protein scarcity, through either an increase in protein supply or reduction in protein demand, results in reduced nematode egg excretion and worm burdens during the periparturient period (Houdijk and Athanasiadou, 2003). Whilst this reduced degree of parasitism indirectly suggests that such nutritional effects are mediated through changes in host immune responses, there is only limited direct evidence for this. A rodent model may be used for directly assessing immune responses that underlie nutritional control of nematode parasites. There is indirect evidence that lactating rats undergo a breakdown of immunity to the intestinal nematode Nippostrongylus brasiliensis (Houdijk et al., 2003). Provided that this breakdown is sensitive to protein nutrition, this model may be used for elucidating interactions between nutrition and immunity to parasites. Therefore, we assessed whether breakdown of immunity to N. brasiliensis in the lactating rat is sensitive to host protein nutrition.