Relative bio-availability of phosphorus from Venezuelan raw rock phosphates for poultry

To evaluate the bio-availability of phosphorus in Venezuelan raw rock phosphates, 1260 1-day-old male chicks of the commercial Cobb hybrid strain, fed a basal diet containing 4.14 g kg−1 total phosphorus (P), were assigned to six raw rock phosphorous dietary sources: Riecito (RIO), Lizardo (LIZA), Chiguará (CHIGUA), Jajı́ (JAJI), Monte Fresco (MONTE), Navay (NAVAY) and a reagent grade dicalcium phosphate (DICAL), at three levels of added P (1–3 g kg−1). Growth rate and bone mineralization were used as response criteria. Birds were housed in electrically heated battery brooders. The diets, offered ad libitum, were formulated to be isoenergetic (12.97) apparent metabolizable energy (AME) (MJ kg−1), and to contain protein 240 g kg−1 and calcium 10 g kg−1. At 4 weeks of age, six chicks/treatment were slaughtered and their tibias removed for the determination of density (g cm−3 fresh bone), fat free dry matter, ash, phosphorus and fluorine content (mg kg−1 dry defatted bone and mg cm−3 fresh bone). The body weight of birds (g), at 4 weeks of age, as an average of the three levels of supplemental P, was higher (P<0.05) for the DICAL treatment (1149) than those treatment with CHIGUA (896), NAVAY (862), MONTE (853) and JAJI (830), and intermediate for RIO (966) and LIZA (974). A similar pattern was observed for bone density and ash and phosphorus content. Positive and significant correlations were observed between body weight and intake (r=0.97) and bone mineralization measured as density (r=0.64), ash (g kg−1dry defatted bone: r=0.63; mg cm−3 fresh bone: r=0.73), and P (mg cm−3 fresh bone: r=0.81) content. Relative bio-availability of P of the sources, using DICAL as a reference control (1), were: RIO (0.802), LIZA (0.795), CHIGUA (0.713), NAVAY (0.684), MONTE (0.675) and JAJI (0.618). Increasing dietary fluorine caused greater accumulation of this element in bone, with the highest values (P<0.05) recorded with the MONTE, NAVAY, JAJI and CHIGUA phosphates. The intake of fluorine at levels over 40 mg per day limited productive performance of the chick and restricted bone mineralization.