Phosphorus digestibility in low-phytate barley fed to finishing pigs

Twenty-four crossbred barrows (Camborough 15 Line female × Canabred sire) weighing an average of 51.3 +/- 5.1 kg were used in a trial conducted during two periods according to a completely randomized block design. The pigs were assigned to one of six dietary treatments comprised of a normal two-rowed, hulled variety of barley (CDC Bold) or three low-phytate genotypes selected to contain approximately 68, 41 or 3% of the normal level of phytate. A normal hulless barley (CDC Dawn) and a hulless genotype selected to contain 54% of the normal phytate content were also included. The diets fed contained 99.5% barley and 0.5% chromic oxide. The marked feed was provided for a 7-d acclimatization period, followed by a 3-d fecal collection. At the conclusion of the first replicate, the pigs were assigned to different treatments and the procedure was repeated resulting in eight observations per treatment. Selection for phytate content had no effects on the apparent fecal digestibility of dry matter, crude protein or gross energy (P > 0.05). The digestibility coefficients for dry matter and energy were significantly higher for the hulless varieties of barley than the hulled genotypes. Phosphorus digestibility increased as the level of phytate in the barley declined. The linear relationship relating phosphorus digestibility (y) to phytate content (x) was: y = 67.7 − 12.54x (r2= 0.64; P < 0.0001).