THE BIOAVAILABILITY OF PHOSPHORUS FROM CANOLA-MEAL AS MEASURED BY HOLSTEIN CALVES AND MOBILE BAG TECHNIQUE

Forty-two male Holstein calves were randomly assigned in a split-plot design to seven dietary treatments. These consisted of a basal diet wi th 0.25% phosphorus (P) and experimental diets supplemented with canol a meal (CM) or Biophos to provide P levels of 0.32%, 0.36% and 0.40%. All diets were formulated to be isocaloric; however, added CM increase d crude protein concentration. Dietary protein thus varied from 14% to 18% (dry matter (DM) basis). The calves were placed on test at 6 week s of age for a 10 week period. Feed intake, weight gain, feed per kilo gram gain, plasma inorganic P, bone ash, bone P, bone Ca and the break ing force of the eighth and ninth ribs were measured. DM consumption, weight pin and feed per kilogram gain were not affected by dietary P ( P>0.05). Each increase in P with CM resulted in an increase in plasma P (P<0.05). Supplementary Biophos resulted in an increase in plasma P (P<0.05) with no differences among the three levels of added Biophos. The breaking force, bone ash and bone P content of the eighth and nint h ribs were not affected by P levels (P>0.1). On the basis of blood P response to increased dietary P, availability of P from CM was at leas t equal to the inorganic P source. In situ P disappearance in the rume n was higher (P<0.05) for soyabean meal (SBM) than for three of the fi ve CM-supplemented diets and similar for two CM samples at 12 h and 16 h of rumen fermentation. From the lower GI tract, the in situ P disap pearance was not different (P>0.05) for SBM compared with CM or among CM samples when pepsin-HCl predigestion was used.