Interactive effects of copper sources and superdose phytase on growth performance, nutrient digestibility and tissue mineral concentrations in nursery pigs

This study investigated the interactive effects of copper (Cu) sources and superdose phytase on growth performance, nutrient digestibility and tissue mineral concentrations in nursery pigs. A total of 288 weaning barrows (PIC 337 × 1050, Hendersonville, TN; BW = 6.06 ± 0.99 kg), blocked by BW, were randomly allotted to 1 of 6 dietary treatments, with 12 pens/treatments and 4 pigs/pen. Six dietary treatments were arranged in 3 × 2 factorial design, with 3 Cu sources [125 ppm Cu from copper sulfate (CuSO4), tribasic copper chloride (TBCC) or copper methionine hydroxy analogue chelate (Cu-MHAC, MINTREX® Cu, Novus International, Inc.), respectively] and 2 phytase levels [0 or 1500 FTU/kg from phytase PHYTAVERSE® G10 (Novus International, Inc.)]. There was an interaction (P = 0.05) between Cu sources and superdose phytase on ADG during d 0-41, with the improvement by superdose phytase being 25.84, 33.96 and 40.85% when the Cu sources were CuSO4, TBCC and Cu-MHAC, respectively. Superdose phytase significantly (P < 0.01) reduced F:G during d 0 to 41. Cu-MHAC led to greater ATTD of neutral and acid detergent fiber (NDF, ADF, respectively; P = 0.01) than CuSO4 and TBCC, respectively. Cu-MHAC led to greater (P = 0.03) ATTD of P than CuSO4, with TBCC intermediate. There was no interaction (P > 0.10) between Cu sources and superdose phytase in terms of nutrient digestibility and tissue mineral concentrations. Cu source did not (P > 0.10) affect tissue mineral concentrations; however, superdose phytase increased (P ≥ 0.05) bone Ca and P concentrations. In conclusion, Cu-MHAC may improve the efficacy of superdose phytase in terms of growth performance, most likely by improving phytate P hydrolysis and therefore providing more P for absorption. Superdose phytase is effective in improving growth performance of nursery pigs, mainly driven by increased Ca and P absorption and utilization.