This study investigated the effect of different levels and consumption periods of Aspergillus oryzae meal on performance, carcass characteristics, blood variables, and immunity of broiler chickens. A total of 270 (male and female) Ross 308 chicks were randomly assigned to 9 treatment groups. Two levels (2 g/kg diet and 4 g/kg diet as-fed) of Aspergillus oryzae meal (AO) and 4 consumption periods of AO (starter, grower, finisher, and entire period) in a 2 × 4 factorial arrangement were used. Compared with control, AO used during the entire rearing period increased weight gain, reduced relative weight of abdominal fat, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) serum levels, and increased antibody titers against influenza and Newcastle disease vaccination and sheep red blood cells injection. Few differences in the variables considered were found if AO was added to broiler diets only during specific consumption periods, and between the two supplementation levels of AO. In conclusion, the addition of AO to the broiler diet can have beneficial effects in terms of performance, carcass composition, and health, but these positive effects were mainly reached adding AO for the entire rearing period.

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