Effects of low-level infections by coccidia and roundworms on the nutritional status of rats fed an adequate diet.

Experiments were conducted on male, Sprague-Dawley rats of the same age fed a standard laboratory diet to determine the comparative effects of single and concurrent subclinical infections by coccidia (Eimeria nieschulzi) and roundworms (Nippostrongylus brasiliensis) on nutritional status and metabolism. All infections produced anorexia, but it was more prolonged and intense with the concurrent ones. Feed:gain ratios were increased only by infections by nematodes alone, but average daily gains were reduced beyond the effect of anorexia (i.e., "specifically") only with the double infections. Infections by coccidia only, but not by nematodes only, specifically reduced the apparent digestibility of dry matter, organic matter and N; whereas only the apparent N digestibility was specifically reduced by the double infections. Balances of N were reduced in infected rats and pair-fed controls during anoretic periods, but significant differences between the daily means for infected and pair-fed rats occurred only erratically. Specific increases in urinary N loss did not occur with the single infections, but occurred on 2 d with the double ones. Increased losses of fecal N occurred with both coccidial and double infections, but they were much more pronounced in the latter. No effects of infection on the balances or carcass contents of Ca and P occurred. The only significant differences between mean empty carcass densities occurred with the double-infected and free-fed uninfected groups, with the mean for the uninfected group being the higher.