Interrelationship of dietary phosphorus, aluminum and iron on performance and tissue mineral composition in lambs.

A 76-d feeding trial was conducted with 24 wether lambs (31 kg, initially) to study the interrelationships among dietary P, Al and Fe. A 2 x 2 x 2 factorial arrangement of treatments included two concentrations of supplemental P (0 or .25%) with added P as NaH2PO4, two levels of supplemental Fe (0 or 760 ppm) with Fe added as ferric citrate and two levels of supplemental Al (0 or 1,450 ppm) with Al added as AlCl3 . 6H2O. The basal diet contained .17% P, 40 ppm Fe and 168 ppm Al. Phosphorus increased (P less than .01) feed consumption, but Fe (P less than .01), with added P improving and Fe or Al depressing gain. Additional P improved gain (P less than .05) and intake (P less than .01) in the presence of high Al and intake (P less than .05) when dietary Fe was high. Serum P was increased (P less than .01) by high dietary Fe and reduced (P less than .01) by Al. High dietary P increased (P less than .05) serum MG. High dietary Fe increased (P less than .01) hemoglobin and hematocrit and increased (P less than .01) Fe storage in liver, kidney, spleen and muscle but decreased (P less than .01) kidney Zn concentration. High dietary Al increased (P less than .01) liver Fe and kidney Zn levels but decreased kidney P and Mg (P less than .05) and bone ash and Mg (P less than .01). Based on these studies, additional dietary P appeared beneficial in overcoming the adverse effects of high dietary Al or Fe.