In the present study, the effects of phytase supplementation with and without citric acid (CA) on growth performance, carcass characteristics and serum minerals concentration, tibia and shank characteristics, and phosphorus (P) retention were determined in broilers fed non-phytate P deficient diets. Ninety six one day old male broilers (COBB-500) were divided into four groups (twenty four birds each, and were fed one of the following diets until they were 35 days old: positive control (PC) diet formulated based on the NRC (1994) recommendations, negative control (NC) diet containing 0.20 % lower non-phytate P than that in the PC diet, and two other diets were formulated by adding only phytase (500 FTU/kg of feed) or phytase with CA (500 FTU/kg of feed with 2 % CA). At the age of 36 day, birds were sacrificed, samples were collected, processed, and then analyzed. Compared with the PC group, NC group showed impaired growth performance (final BW, BW gain, and FCR), serum P concentration, tibia and shank characteristics (dry weight, contents of ash and P). However, in most cases, these impairments were ameliorated (P
Key words: birds, blood, bone, growth performance, phosphorus retention
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