Biological availability of various sources of Ca and P supplements in young chicks

This experiment was carried out to evaluate biological availability of Ca and P in 4 different sources of tricalcium phosphate in young chicks. One hundred and twenty five-day-old male Single Comb White Leghorn chicks (10 treatments x 3replication x 4chicks) were used in trial 1 and 2, respectively, for 12 days of feeding period. Trial I was to evaluate the availability of phosphorus in the supplements. Standard purified diets were prepared to 0.07, 0.14 and 0.21 % P using a mixture (1 : 1) of NaH2PO4 and KH2PO4 as the reference Phosphorus sources. Bone breaking strength of the tibia determined by an Instron instrument appeared inadequate to be used as a criterion due to very high variations of the measurement within a treatment. Thus, tibia bone ash content was utilized as a criterion to evaluate the biological availability of phosphorus in the supplements. The levels of the biological availability of the four different sources of dicalcium phosphate were 77.1, 91.0, 96.4 and 95.5 %, respectively, and those of the three tricalcium phosphate sources were 94.1, 95.0 and 99.5 %, respectively. Trial 2 was to determine the levels of Ca biologically available in the supplemants. Standard purified diets were made to supply 0.2, 0.3 and 0.4 % Ca using CaCO3 as the reference calcium source. When bone ash content was utilized as a criterion for the availability, the levels of calcium biologically available to the chicks were 78.3, 234.1, 87.6 and 244.5 %, respectively, for the 4 different sources of dicalcium phosphate and 99.5, 84.0 and 101.5 %, respectively, for the 3 different sources of tricalcium phosphate. The observation that two calcium sources appeared to be utilized with an unusual efficiency can hardly be explained at this moment. When they were reevaluated on the basis of body weight gain, the availabilities of the four sources of dicalcium phosphate were 89.2, 58.2, 104.1 and 103.1 % and of the three tricalcium phosphate were 112.6, 106.0 and 96.3 %, respectively