Improved mineral utilisation in grower-finisher pigs fed a diet supplemented with graded amounts of two phytases

Dietary phytase, when used correctly, will prevent possible phosphorus (P) deficiency, reduce the P content in animal waste and maintain animal well-being. The aim of this study was to evaluate the effects on P and calcium (Ca) utilisation, plasma indices and bone strength of a C. braakii-(Ronozyme HiPhos) and an E. coli-(Quantum Blue) derived 6-phytase at high dosages in grower-finisher pigs. The hypothesis tested was that high phytase inclusion levels would give additional benefit in pigs by improving mineral utilisation.

An experiment was conducted with 64, 70-day-old pigs (Large-White × Redon) having an initial body weight of 23.5 ± 1.96 kg (mean ± SE). Pigs were randomly allotted into eight groups of eight animals each. They were fed ad libitum for 84 days with diets based on corn, soybean meal and barley. Diets were a positive control (PC) formulated to meet the animal requirements for the finishing period according to NRC (2012) [total P, 0.47%; total Ca, 0.80%; crude protein (CP), 150 g/kg; metabolisable energy (ME), 13.4 MJ], or a matrix control diet (MC) with reduced nutrient content [total P, 0.37%; total Ca, 0.65%; CP, 145 g/kg; ME, 13.1 MJ]. The MC diets were supplemented with Ronozyme HiPhos at 1000 (H1000), 2000 (H2000) and 3000 U/kg (H3000), and with Quantum Blue at 500 (Q500), 1000 (Q1000) and 1500 U/kg (Q1500). The coefficient of total tract apparent digestibility (CTTAD) of P and Ca, excretion of P and Ca, plasma indices and metacarpal bone characteristics were evaluated at the end of the trial. Plasma myo-inositol (INO) was analysed according to Leung et al. (2011) and the other parameters using the methods described in AOAC (2012). Data were examined by ANOVA and differences between groups were determined by the Student-Newman-Keuls multiple-range test (significant at P < 0.05).

The CTTAD of P was improved (P < 0.05) and P excretion reduced (P < 0.05) in all phytase groups (Table 1). The Ca excretion was lower (P < 0.05) with the phytase and MC treatments in comparison to the PC diet, and was not different (P > 0.05) between phytases or inclusion concentrations. Plasma P was increased (P < 0.05) in all phytase-fed pigs whereas plasma Ca was higher (P < 0.05) in the PC group than in the other groups (Guggenbuhl et al. 2012a). Plasma INO, the end product of phytate degradation, was increased (P < 0.05) in the H100, H2000, H3000, Q1000 and Q1500-fed pigs. Compared to the MC treatment group, bone ash and breaking force were improved (P < 0.05) in all phytase groups.

Data from the present study showed similar effects for both enzymes. The highest dosages from each of both phytases had beneficial effects on all measures, thereby compensating for reduced nutrient levels and further reducing P and Ca supplementation in pig diets (Guggenbuhl et al. 2012a, 2012b). The increased plasma INO could be partly involved in the bone strength improvements (Croze and Soulage 2013).

Table 1.  Mineral utilisation in grower-finisher pigs fed graded amounts of two different phytases