Effect of Replacement of Dicalcium Phosphate by Heat Treated Rock Phosphate With and Without Phytase on Performance and Nutrient Utilization in Layers

This study was planned to see the effect of heat treated rock phosphate without and with phytase, instead of DCP on performance, nutrient utilization and serum enzymic activity and serum minerals concentration in layers. Two hundred and ten layers (WLH, Babcock BV-300) of 20 weeks age with identical weights were randomly distributed to 21 replicates of 10 layers each and were allotted to 7 dietary treatments. In control group (T₁), DCP was used as a sole source of phosphorus. Diets 2, 4 and 6 (T₂, T₄ and T₆) were tested to know the usefulness of using heat-treated rock phosphate (HTRP) replacing DCP @ 60%, 80% and 100% in comparison to T₁. While, diets 3, 5 and 7 (T₃, T₅ and T₇) were similar to T₂, T₄ and T₆ except the addition of phytase enzyme (@1 Phytase unit= 4.0 g of P) in those diets. Experiment was conducted for 2140 weeks (Layer phase). The cumulative performance of layers indicated that use of HTRP instead of DCP up to 60% level increased their weight gain, feed intake and % HDP. However, feed intake and % HDP was maximum in birds assigned 80% HTRP instead of DCP. The egg weight, FCR (Kg feed/dozen as well as per Kg egg), age of first egg laid, HU and egg shell thickness were not influenced due to levels of HTRP. However, 80% HTRP (T₁₂) instead of DCP produced better egg quality traits (shape index, albumen index and yolk index). The DM utilization and retention of nutrients (CP, EE, CF, NFE, Ca and P) was also significantly higher in these birds but complete replacement of DCP reduced their DM utilization and retention of nutrients significantly. Supplementation of phytase with different levels of HTRP did not influence the FCR (Kg feed per dozen as well as per Kg eggs), % HDP, egg weights and age at first egg laid. However, when supplemented with 100% HTRP, it increased the feed intake, body weight gain, DM utilization and retention of Ca. Similarly, use of phytase with varying levels of HTRP also did not influence the egg quality traits (albumen index, yolk index, HU and egg shell thickness), retention of nutrients (CP, EE, CF, NFE and P), concentrations of serum enzymes (ALT, AST, and ALP) and minerals (Ca and P). Supplementation of phytase with 100% HTRP increased DM utilization and Ca retention significantly. Use of graded levels of HTRP instead of DCP did not affect serum concentrations of enzymes (ALT, AST and ALP) and minerals (Ca and P) except F which increased when HTRP was increased over 60% instead of DCP. Feed cost (Kg feed/dozen or per kg egg) was lowest in layers assigned 80% HTRP instead of DCP. Hence, DCP replaced to the extent of 80% and 100% HTRP along with phytase was beneficial in the mineral mixture of layers.