A 21 d study was conducted to determine the effects of a low phytic acid mutant barley (Hordeum vulgare L., MB) containing the lpal-l allele compared with a near-isogeneic wild-type hybrid barley (NB) on phosphorus (P) utilization by turkey poults. One-day-old male poults (n = 150) were randomly allotted to 5 treatments (6 pens of 5 poults per treatment). The MB contained 0.21% nonphytate (estimated available) P (aP) and 0.35% total P (tP), whereas NB contained 0.11% aP and 0.35% tP. The 5 treatments were: (A) NB diet containing 0.30% aP and 1.0% Ca; (B) MB diet containing 0.36% aP and 1.0% Ca; (C) NB diet similar to diet A but with KH2 PO4 added to increase the aP to 0.36% to equal the aP in diet B; (D) MB diet containing 0.60% aP and 1.2% Ca; and (E) NB diet containing 0.60% aP, and 1.20% Ca. Growth performance, toe and tibia ash were similar in poults fed diets B and C, and in poults fed diets D and E. Poults fed MB diets retained more P (P<.05) than poults fed the corresponding NB diets. Results indicate that P in MB is more available than P in NB, and decreasing the phytate content did not compromise the nutritional value of MB. A second 35 day experiment was conducted with crossbred barrows (n = 35) averaging 13.5 kg to evaluate MB compared to NB. The five treatments (T) were: (1) a NB diet containing 0.14% aP and 0.32% tP, (2) a MB diet containing 0.22% aP and 0.32% tP, (3) diet 1 with monosodium phosphate added to increase aP to 0.22% to equal the aP in diet 2, (4) a NB diet containing 0.57% tP, 0.30 aP and 0.65% Ca, and (5) a MB diet containing 0.50% tP, 0.30 aP and 0.65% Ca. Diets 1 to 3 were supplemented with whey protein concentrate, blood cells and ground limestone to bring Ca to 0.50%. Diets 4 and 5 were supplemented with soybean meal, ground limestone and dicalcium phosphate. Pigs were housed in individual pens and fed to appetite. Pig performance, and metacarpal and radius bone breaking strength were similar (P>0.04) for T2 and T3, and for T4 and T5. The MB reduced (P<0.03) fecal P excretion 55% compared to NB (1.8 vs 4.0 g/d) when barley was the only source of phytate in the diet. With soybean meal as the protein source, fecal P excretion was reduced (P<0.14) 15% by MB compared to NB (3.7 vs 4.4 g/d). The absorption and retention of P (g/day) were higher (P<0.05) for the diets containing MB compared to NB. Calcium absorption was also increased (P<0.05) with MB compared to NB in the diets where barley was the only source of phytate. In conclusion, MB significantly reduced fecal P excretion and increased P absorption and retention compared to NB. The absorption of Ca was also increased by MB compared to NB. Pig performance and bone strength confirmed our estimate of 0.21% aP in the low phytic acid barley.