High dose of phytase on apparent and standardized total tract digestibility of phosphorus and apparent total tract digestibility of calcium in canola meals from Brassica napus black and Brassica juncea yellow fed to growing pigs

A total of 42 barrows weighing 19.8 +/- 1.22 kg were fed seven diets to give six replicates per treatment. The experiment was conducted in a factorial arrangement with factors being (1) two canola meals (CM) types and (2) three phytase levels (0, 500, and 2500 FTU kg(-1)). The basal endogenous phosphorus (P) losses and standardized total tract digestibility (STTD) was calculated using the P-free method. There was no effect of CM types on feed intake and fecal P output, but an interaction effect was observed for P intake (CM x phytase; P < 0.05). Supplementation of phytase (2500 FTU kg(-1)) reduced (P < 0.001) fecal P output (g d(-1)), and the output was reduced by 58% in Brassica napus black (BNB) and 64% in Brassica juncea yellow (BJY) diets. Supplementation of phytase improved (P < 0.001) both apparent total tract digestibility (ATTD) and STTD of P in both BNB and BJY, regardless of dose. The basal endogenous P loss (EPL) was determined to be 111.28 +/- 35.09 mg kg(-1) of dry matter intake (DMI). There was no further improvement in STTD of P when phytase was increased from 500 to 2500 FTU kg(-1) in both CM types. The ATTD of calcium (Ca) was increased (P < 0.001) in BNB and BJY when phytase was supplemented at 500 and 2500 FTU kg(-1). The results, therefore, indicate that supplementation of phytase at 500 FTU kg(-1) improved both ATTD and STTD of P in two CM types, but a super dose of 2500 FTU kg(-1) had no additional benefit. Similarly, ATTD of Ca was increased when phytase was supplemented at 500 FTU kg(-1) without further improvement at 2500 FTU kg(-1).