Investigation on bioavailability of rumen bacterial and protozoal phosphorus using a chick-model

Ruminal bacteria and protozoa provide excellent organic phosphorus (p) sources for the host animal. this experiment was conducted to compare the bioavailability of bacterial and protozoal p in comparison with that of dicalcium phosphate (dcp) as a reference phosphorus source. bacteria and protozoa were isolated from the rumen contents of dairy cows and the chick-model was used to determine the phosphorus bioavailability. fifteen day-old chicks were used in a completely random-ized design with 4 treatments consisting of a control diet (without p, as a basal diet), bacterial p+basal diet, protozoalp+basal diet, and dcp+basal diet. phosphorus balance was selected as the response criterion for phosphorus bioavailability assessment, using multiple linear regressions. the results showed a higher phosphorus bioavailability of protozoal p and dcp compared with bacterial p (p<0.05); with no significant difference between protozoal p and dcp. relative phosphorus bioavail-ability values of bacterial source ranged from 0.451 to 0.495, using protozoal source as reference. bioavailability of p in rumen protozoa, relative to that in dcp, was high (approximately 97%); there-fore rumen protozoa may serve as an important source of organic p in ruminants for providing a sig-nificant portion of phosphorus requirements.