1. The effect of A. subrufescens and P. ostreatus mushrooms as an alternative to antibiotics (avilamycin or monensin sodium) on performance, intestinal morphometry, immunity, and biochemical profile of broilers challenged with Eimeria spp. was studied from 1 to 42 d old. A total of 900 male Cobb (R) broiler chicks were distributed, according to a completely randomised design, into five treatments with six replicates each. 2. The treatments consisted of: negative control (NC) - basal diet (BD) with no anticoccidial or antibiotic (non-challenged birds); negative control challenged (NCC) - NC fed to Eimeria spp. challenged birds; BD with 0.2% A. subrufescens inclusion for challenged birds (As), BD with 0.2% P. ostreatus inclusion for challenged birds (Po); and a positive control - BD with anticoccidial and antibiotic inclusion for challenged birds (ATB). 3. At 11 d.o., the birds were each inoculated orally with 1 ml solution containing 2 x 10(5) sporulated oocysts/ml Eimeria acervulina and 2 x 10(4) sporulated oocysts/ml E. maxima and E. tenella. 4. Birds subjected to Eimeria spp. challenge up to 21 d of age had greater crypt depth, indicating that the presence of undesirable microorganisms had an effect on cell proliferation. 5. At 21 d old, the birds receiving ATB had higher average weight gain (AWG), feed intake (AFI), and feed conversion ratio (FCR) compared to those fed diets supplemented with mushrooms (As or Po). For the total rearing period (42 days), the birds that received ATB had higher AWG and AFI (P < 0.001) compared to those that received As or Po diets. Feeding avilamycin did not affect (P = 0.0676) FCR compared to the As or Po diet groups. 6. From the morphometric and blood analyses there were no differences between broilers fed ATB, Po or As diets in either rearing periods. However, Po and As supplementation lowered blood triglyceride levels. At 21d there was a difference (P < 0.05) for MCV and haemoglobin, in which the mushrooms were similar to the antibiotic. At 42 d, there was a difference (P < 0.05) in haematocrit, erythrocyte, MCV, H: L, protein and albumin variables, in which the use of mushrooms was similar to the positive control, demonstrating that both (mushrooms and antibiotics) promoted a certain improvement in the health of the chickens. 7. A. subrufescens and P. ostreatus can be used in broiler diets without compromising intestinal or haematological status, however, these ingredients did not result in improvements in performance.
