Response of laying hens to diet inclusion of canola meal as influenced by dietary nonphytate phosphorus level and microbial phytase supplementation

An experiment employing a factorial arrangement of three levels (0, 8 and 16%) of canola meal (CM), two levels (0.15 and 0.25%) of nonphytate phosphorus (NPP), and two levels (0 and 450 unit/kg; as fed basis) of microbial phytase was conducted using 216 Hy-Line W36 laying hens from 39 to 47 weeks of age. The birds receiving CM consumed more (P < 0.05) feed than birds receiving corn-soybean meal (SBM) diets. During the second 4 weeks of the experiment (44 to 47th weeks of age), egg production and egg mass were lower (P < 0.05) for birds receiving corn-SBM diet containing reduced NPP level; however, the adverse effects of reduced NPP were overcome by phytase supplementation (P < 0.05). During the second 4-week (44 to 47th weeks of age) and over the whole experiment (39 to 47th weeks of age), production of abnormal eggs was increased (P < 0.05) by feeding reduced NPP level; phytase supplementation decreased (P < 0.05) egg abnormality only when added to this diet. At the first egg sampling (43rd week of age), egg shape index and eggshell thickness were increased (P < 0.05) by phytase supplementation. Reduced NPP level caused a lower eggshell thickness in hens fed corn-SBM diet (P < 0.05). At the second egg sampling (47th week of age), birds fed corn-SBM diets or reduced NPP level produced eggs with lower (P < 0.05) shell thickness, whereas dietary phytase supplementation reversed these adverse effects (P < 0.05). Reduced NPP level increased serum thyroxine concentration in birds fed corn-SBM-CM diets (P < 0.05). The results showed that CM can be included in laying hen diets up to 16% during 39 to 47 weeks of age without any adverse effect on their health and productivity. Moreover, the results indicated that reduction of NPP level in corn-SBM-CM diets had little effect on performance and eggshell quality. The adverse effects of lowering NPP level in corn-SBM diets could be substantially reduced by phytase supplementation.