Comparing the Efficacy of Varieties, Low and High Phytase-expressing Corn, at Equivalent Phytase Levels on Broiler Performance and Bone Ash

Abstract

Objective: A study was conducted to compare the efficacy of two varieties of corn-expressed phytase [low specific activity (203) and high specific activity (1203)] at equivalent FTU kg^–1 in broilers. Materials and Methods: Day-old Cobb 500 male broiler chicks were randomly allocated to one of 10 dietary treatments: Positive Control (PC, standard Ca and aP); Negative Control (NC, -0.15% Ca and aP), NC +0.5 kg MT^–1 203, NC+1.0 kg MT^–1 203, NC +2.0 kg MT^–1 203, NC +3.0 kg MT^–1 203, T7, NC+0.18 kg MT^–1 1203, NC+0.36 kg MT^–1 1203, NC+0.72 kg MT^–1 1203, NC +1.08 kg MT^–1 1203. All birds were weighed on day 14, 28 and 42 to obtain performance parameters: Body weight (BW), feed consumption (FC) and feed conversion ratio (FCR). On d28, left tibias were sampled from 3 birds per pen, for a total of 30 birds per treatment to determine tibia bone ash. Results: On day 14 and d28, birds fed diet supplemented with 203 (day 14, 0.50±0.00 kg, day 28, 1.80±0.00 kg) and 1203 (day 14, 0.50±0.01 kg, day 28, 1.81±0.01 kg) were heavier (p<0.05) than PC (day 14, 0.41±0.00 kg, day 28, 1.65±0.03 kg) and NC (day 14, 0.41±0.00 kg, day 28, 1.50±0.03 kg). On day 42, birds fed diet supplemented with 203 (3.41±0.04 kg) and 1203 (3.45±0.03 kg) were heavier (p<0.05) than NC (3.09±0.07 kg). On day 0-28 and day 0-42, birds fed diet supplemented with 203 (day 0-28, 1.41±0.00, day 0-42, 1.61±0.01) and 1203 (day 0-28, 1.41±0.00, day 0-42, 1.59±0.01) improved FCR (p<0.05) compared to NC (day 0-28, 1.52±0.01, day 0-42, 1.67±0.01). On day 28, birds fed diet supplemented with 203 and 1203 (51.69±0.08%) improved bone ash (p<0.05) when compared to NC (47.95±0.95%). Conclusion: Both low specific activity and high specific activity corn-expressed phytase varieties improved BW, FCR and bone ash compared to PC. Inclusion of either phytase improved broiler performance and bone mineralization in Ca and aP reduced diets and there were no discernible differences in the efficacy of these two enzymes at the tested loading rates.