One hundred and ninety two day-old broiler chicks (Vencobb) were divided into four identical groups having four replicates in each group with 12 birds in each replicate and allotted randomly into four dietary treatments viz., T1, T2, T3 and T4 for eight weeks. The treatments consisted of a standard broiler ration (SBR) with 0.5 per cent available phosphorus (T1), low available phosphorus broiler ration having 0.3 per cent available phosphorus (LAPBR) and 3.0 per cent citric acid (T2), LAPBR supplemented with 700 U of microbial phytase/kg feed (T3) and LAPBR with 1.5 per cent citric acid and 350 U of microbial phytase /kg feed (T4). Protein intake (g) of the birds at replication wise was calculated at fortnightly intervals, based on the data on feed intake and protein content of feed. Protein efficiency ratio (PER; g body weight gain/g of protein consumed) was calculated based on the data on body weight gain and protein intake. Synergistic improvement (P<0.01) in cumulative protein intake was noticed in T4 both at sixth and eighth week of age. Regarding the cumulative PER, the birds belonging to various treatments T1, T2, T3 and T4 recorded similar PER (P>0.05) at eighth week and significantly higher PER (P<0.05) in T2 as well as T4 at sixth week. The values were 2.03, 2.14, 2.05 and 2.13 at sixth week and 1.89, 1.97, 1.94 and 1.96 at eighth week for T1, T2, T3 and T4, respectively. The results indicate that birds maintained on low phosphorus diets with additives (T2, T3 and T4) performed equally good compared to control group maintained on SBR, suggesting the favouring effect citric acid and/or microbial phytase on protein utilization
