The bioavailability of phosphorus from canola meal in comparison with an inorganic phosphorus source and soybean meal

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Omole, Rose Cecilia
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Forty-two male Holstein calves were randomly assigned in a split-plot design to four dietary treatments. The dietary treatments consisted of a basal diet wlth 0.25% phosphorus (P) and experimental diet supplemented with canola meal (samples A, B, C, D, E) or Biophos to provide P levels of 0.32, 0.36 and 0.40%. All diets were isocaloric; however, added levels of canola meal increased crude protein levels. Dietary protein level varied from 14 to 18% (DM basis). Dietary treatments were arranged in a 3X2 factorial. Calves were fed whole milk for four weeks plus ad libitum calf starter. The calves were placed on test at 6 weeks of age for a ten-week period. Feed intaker weight gain, feed per kg gain, plasma inorganic P, bone ash, bone P, bone Ca and the breaking force of the eighth and ninth ribs were the response criteria used to measure P availability. Dry matter consumption, weight gain and feed per kg gain were not affected by dietary P level (p > 0.1). Supplementation with P increased plasma P (p < 0.05). Each increase in P level with canola meal resulted in an increase in plasma P level (p < 0.05). The first level of supplementary Biophos resulted in an increase in plasma P level (p < 0.05) with no differences among levels of added Biophos. The breaking force, bone ash and bone P content of the eighth and ninth ribs were not significantly affected by P levels (p > 0.1). Based on blood P response to an increased dietary level of P, availability of P from canola meal was at least equal to the inorganic P source. In situ P disappearance in the rumen was significantly (p < 0.05) lower for SBM compared with canola meal samples B, D, and E at 12 and 16 h of rumen fermentation. From the lower gastrointestinal tract, the in situ P disappearance was not significantly (p < 0.05) different between SBH and CM when pepsin HC1 predigestion was used.