Biological Availability of Phosphorus in Rice Bran and Wheat Bran as Affected by Pelleting

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Abstract
Eight-day-old crossbred chicks were used in a series of five assays to evaluate the biologically available phosphorus in ground and steam -pelleted rice bran and wheat bran. Tibia ash was used as the response criterion, and regression analysis was used to evaluate tibia ash as a function of phosphorus intake. In each of the first three assays a standard curve was established by feeding graded levels of KH2 PO4. Estimates of phosphorus availability were then made using the slope-ratio technique. Available phosphorus was estimated by comparing the regression coefficient (mg tibia ash/mg phosphorus intake) of the standard KH2PO4 curve with the regression coefficient of the curve established by feeding graded levels of the test phosphorus source. Available phosphorus was calculated to be .23% of the rice bran and .38% of the wheat bran on an as fed basis. Compared to total phosphorus, the availability of phosphorus was 17.6 and 23.0% for rice and wheat bran, respectively. Pelleting failed to improve the available phosphorus in either test ingredient. In two subsequent assays it was shown that (1) dietary organic phosphorus sources had no effect on utilization of phosphorus from inorganic sources and (2) addition of 13% corn oil did not influence phosphorus utilization.