P. GangadeviT. HARIHARAN2020-01-092020-01-092003http://krishikosh.egranth.ac.in/handle/1/5810140064An investigation spread over a period of eight weeks was carried out to study the effect of citric acid and microbial phytase (Natuphos®-5000G) on nutrient utilization and growth performance in broiler chicken. One hundred and ninety two day-old broiler chicks (Ven cob) 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., Tl, T2,13 and T4. The treatments consisted of a standard broiler ration (SBR) with 0.5 per cent available P (Tl), low available P broiler ration having 0.3 per cent available P (TAPER) and 3.0 per cent citric acid (T2), TAPER supplemented with 700 U of phytase/kg feed (T3) and TAPER with 1.5 per cent citric acid and 350 U of phytase/kg feed (T4). All the rations were formulated as per EIS specifications except in the level of available P. Effect on body weight, weight gain, feed efficiency, protein efficiency, DM retention, nitrogen balance, mineral availability, serum and tibial mineral contents, processing yields and livability of birds were the criteria employed for evaluation. Eody weight and weight gain of the experimental birds were significantly influenced by the dietary treatments. Maximum weight and weight gain were recorded in T4 followed by T2, T3 and Tl in the descending order, indicating the positive and synergistic effects of citric acid and phytase on phosphorus utilization and growth. Cumulative feed intake of experimental birds was significantly (P<0.01) enhanced in the additive supplemented groups over the control, the highest feed intake being noticed in T4 followed by T2, T3 and Tl. Cumulative FCR did not differ significantly (P>0.05) between treatments. However, comparatively better feed efficiency was recorded in citric acid and phytase groups (T2, T3 and T4) at sixth week and comparable values at eighth week with the control group (Tl). Cumulative PER also showed similar trend in eight week with significantly high (P<0.05) PER in T2 and T4 at sixth week. Though not differed significantly, better DM retention, nitrogen balance, per cent retention and reduced nitrogen excretion were noticed in T2, T3 and T4 than Tl. Availability of P, Mg, Zn and Mn were enhanced (P>0.05) in T2, T3 and T4 by citric acid and phytase addition compared to T1 group on SBR. Mg and Mn availability were significantly influenced by dietary treatments with highest availability of Mg and Mn noticed in T3 (P<0.05) followed by T4, T2 and Tl. The excretion of P was significantly reduced (P<0.05) in T2, T3 and 14 on citric acid and /or phytase supplementation. Weight of dried tibia was significantly high (P<0.05) in T4 followed by T2, T3 and Tl at sixth week. Per cent tibial ash at sixth and eighth week were also high (P>0.05) in T2, T3 and T4 compared to Tl on SBR which could indicate that citric acid and/or phytase favour P utilization and bone development. No significant difference could be noticed in tibial and serum Ca, P, Mg, Zn and Mn except for a significantly high tibial Mg (P<0.05) in T4 and serum Zn (P<0.05) in T3 at sixth week. Serum alkaline phosphatase was significantly reduced (P<0.01) with maximum reduction in T4 followed by T3, T2 and Tl. Birds of citric acid, phytase and combination group though maintained on low P diet registered no significant difference in per cent dressed yield, ready-to-cook yield, giblet yield, abdominal fat yield and livability, when compared to Tl fed on SBR. Regarding the cost of production as feed cost/kg gain, phytase group (T3) recorded the lowest due to high cost citric acid. Overall evaluation of the results of the present study revealed that inclusion of either 3.0 per cent citric acid or phytase (700U/kg feed) or its combination (1.5 per cent citric acid + 350 U phytase/kg feed) in low available P diet (0.3 per cent) resulted in better nutrient utilization and growth performance in chicks than chicks maintained on SBR with 0.5 per cent available P; tending to suggest that available P level in the feed could be reduced by 40 per cent without affecting the performance and health of broiler chicks by dietary inclusion of citric acid and/or phytase.ennullThesis