Energy and nitrogen metabolism of chickens subjected to infection and reinfection with Eimeria acervulina.

1. The effects of E. acervulina on energy and nitrogen metabolism were studied in respiration chambers on four groups of four broilers aged 16 d: group C was infected with 1.1 x 10(6) oocysts/bird on day 1 and fed ad libitum, while groups A, B and D were pair-fed to group C to day 16 of the experiment. On day 17, groups A and C were given 5.0 x 10(6) oocysts/bird and fed ad libitum, while group B was pair-fed to group A and group D was pair-fed to group C to the end of experiment on day 32. 2. Dietary ME as a proportion of gross energy (0.68) and N retention (42 g/100 g N intake) were reduced in the infected group C compared with pair-fed controls (0.75 and 49 g, respectively) for the period 1 to 16 d. Subsequent challenge of group C saw no effects on the two variables, but metabolisability (0.65) and N retention (33 g) were significantly reduced in group A when infected for the first time on day 17. 3. The daily heat production and food intake of group A infected for the first time with E. acervulina on day 17, and group B, their pair-fed controls, were reduced during days 20 to 25 but no such reductions were observed in group C, receiving a challenge dose of E. acervulina, and group D, non-infected pair-fed to group C. The efficiency of utilisation of ME for growth of groups C and D was 0.60 over the 17 to 32 d period. 4. Challenge of immune birds did not affect the apparent digestibility of total minerals, calcium and phosphorus.