Does phytate origin affect phytase response differently?

The objective of the current study was to evaluate the response to phytase, in broilers fed the same amount of phytate P (PP) from SBM and RB, on apparent ileal P digestibility (AIPD) and bone ash % (BAP). A total of 576 Ross 308 male broiler chicks were fed a common corn-SBM-based diet from d 1 to d 15. From d 15 to 23, birds were fed 12 semi-purified diets containing 0.25% PP from either a SBM diet (0.44% total P) or a RB diet (0.35% total P), with limestone used to maintain a 1.45:1 Ca:P ratio in both diets. Phytase (CIBENZA® PHYTAVERSE®, Novus International, Inc., St Charles, MO) was added to SBM and RB diets at 0, 250, 500, 750, 1000 and 2000 FTU/kg in a completely randomized 2×6 factorial design with 8 replicate cages (6 birds/replicate). Digesta from the posterior 2/3rd of the ileum and right tibias were collected on d 23. Excreta were collected daily from d 20 to 23. Data were analyzed by 2-way ANOVA to evaluate the effect of ingredient, phytase and their interaction, and by orthogonal polynomial contrasts to test the linear and quadratic effects of phytase in SBM and RB diets. Results indicated no interaction of ingredient × phytase for AIPD (P>0.05). AIPD was affected by phytase (P<0.01) but not by ingredient (P=0.48). Phytase main effect indicated AIPD values of 43.4, 64.9, 69.6, 73.7, 72.9 and 82.7% for 0, 250, 500, 750, 1000 and 2000 FTU/kg of diet, respectively. Phytase effect was quadratic for both ingredients (P< 0.01). A significant (P<0.01) ingredient × phytase interaction was found for BAP. Supplementing phytase to the SBM diet did not affect BAP (P>0.05), while phytase significantly improved BAP at 250 FTU/kg and beyond for the RB diet. Phytase effect on BAP was quadratic for RB (P<0.01). In summary, phytase supplementation of SBM and RB diets with similar PP content resulted in similar AIPD but different BAP response which could be attributed to differences in Ca content used to maintain Ca:P ratio.

 

Keywords: Soybean meal rice bran phytase P digestibility.