Calcium induced phosphorus deficiency in phytase supplemented broiler diets
A.KOWSIGAN 1, R.G.GLORIDOSS, B.S.V.REDDY,
C. BASAVANTA KUMAR AND B.N.SURESH
Department of Animal Nutrition
VeterinaryCollege, University of Agricultural Sciences
Hebbal, Bangalore- 560 024
A broiler growth cum metabolic trial involving 340 day-old chicks constituting two replications of seventeen experimental groups was carried out. A factorially designed dietary regimen with two levels each of phytase enzyme (625 U/kg and 1250 U/kg), available phosphorus (0.30% and 0.40%), calcium (0.8% and 1.0%) and vitamin D 3 (2000 IU/kg and 4000 IU/kg), which resulted in a set of 16 diets of various combinations was employed. The control diet had BIS (1992) specified level of 1.2 percent calcium (Ca) and 0.5 percent available phosphorus (Pav), and vitamin D 3 was fixed at 2000 IU/ kg. Such diets were isonitrogenous and isocalorific and of both starter and finisher types. Various interactions were studied. In diets containing 0.30 percent Pav and 1.0 percent calcium, the lower level of phytase was more beneficial than the higher level in terms of average cumulative feed consumption (2834 g/bird Vs 2598.5 g/bird), average cumulative body weight gain (1528 g/bird Vs 1421.5 g/bird), livability (75% Vs 50%) and net returns (2.08 Vs 1.42 Rs/kg saleable body weight gain). Under these dietary conditions feed conversion ratio was largely unaffected. The calcium and phosphorus retention values of the three-way interaction effects of phytase (625 U/kg) X Pav (0.3%) X calcium (1%) were 43.19 percent and 48.84 percent respectively while that of phytase (1250 U/kg) x Pav (0.3%) X calcium (1%) was 54.13 percent (Ca) and 51.31percent (P). The higher level of phytase had enhanced the retention of calcium by 10.94 percent and phosphorus retention by a meager 2.47 percent. Phytase while causing increased calcium retention than the phosphorus retention for identical levels of dietary Ca and P, infact lead to calcium induced phosphorus deficiency. Under parallel dietary conditions, the reduction in the dietary level of calcium from 1.0 percent to 0.8 percent restored these performance criteria. Thus supplemental phytase can be detrimental too, unless dietary calcium is lowered.