Effect of Quantum phytase on nutrient digestibility and bone ash in White Leghorn laying hens fed corn-soybean...

The efficacy of an Escherichia coli 6-phytase supplementation (Quantum) on nutrient digestibility-retention and bone ash in laying hens fed corn-soybean meal (CSM) diets was investigated. White Leghorn hens (Shaver and Bovan strains) were fed CSM diets containing 0.35% (positive control, PC), 0.25% (negative control 1, NC1), or 0.15% (negative control 2, NC2) nonphytate P from 21 to 61 wk of age. Six more diets were manufactured by supplementing the negative control diets with 200, 400, and 600 units per kilogram of exogenous phytase resulting in a total of 9 treatments. Each dietary treatment x strain subclass was replicated twice with 6 hens per replication. Fecal and ileal digesta samples were collected at 42 wk of age to determine apparent nutrient digestibility or retention. Left tibiae were collected at 42 and 61 wk of age to determine bone ash. The coefficients for ileal digestibility and fecal retention for protein were higher (P < 0.05) for the unsupplemented negative control treatments compared with the PC. A linear reduction in phytate digestibility and ileal protein digestibility was reported with increasing levels of phytase to the NC1 diet. Phytase addition to the NC1 treatment resulted in a linear decrease in the digestibility of amino acids except for methionine and proline. Significantly higher phytate digestibility was demonstrated with the NC2 treatment containing 400 units per kilogram of phytase compared with the PC. Tibial bone ash percentage was higher (P < 0.05) in 61-wk-old hens fed 200 or 400 units per kilogram of phytase-supplemented NC2 diets. Significantly higher diet AME and fecal protein retention were demonstrated for Shaver hens in comparison to the Bovan hens. Overall, the Quantum phytase was not efficacious at improving nutrient digestibility-retention in laying hens fed CSM diets deficient in nonphytate P.