Improved mineral utilisation in weaned pigs fed a diet supplemented with graded amounts of two phytases

The effects of dietary phytase on mineral utilisation in pigs are well known and documented, but less information has been reported when high dietary inclusion levels are used. The aim of this study was to evaluate the effects on phosphorus (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 one, two and three times their recommended feed inclusion levels in weaned pigs. The study tested the hypothesis that high phytase dosages will give additional benefit in piglets by improving mineral utilisation.

An experiment with 96, 28-day-old weaned pigs (Large-White x Redon) having an initial body weight of 7.91 ± 0.73 kg (mean ± SE) was performed. Piglets were randomly allotted into eight groups of 12 animals each. They were fed ad libitum for 42 days with diets based on corn, soybean meal and rapeseed meal. Diets were a positive control diet (PC) formulated to meet the animal requirements according to NRC (2012) [total P: 0.66%; total Ca: 0.80%; crude protein: 192 g/kg; metabolisable energy (ME): 14.2 MJ], or a matrix control diet (MC) with reduced nutrient content [total P: 0.55%; total Ca: 0.63%; crude protein: 188 g/kg; ME: 14.0 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 P and Ca coefficient of total tract apparent digestibility (CTTAD) and excretion, plasma indices and femur characteristics were evaluated. 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 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-fed pigs (Table 1). The CTTAD of Ca was increased (P < 0.05) and Ca excretion decreased (P < 0.05) in the H2000, Q1000 and Q1500 treatments in comparison to the MC diet. Plasma P was increased (P < 0.05) in all phytase-supplemented pigs whereas plasma Ca was only reduced (P < 0.05) in the H2000 group compared to the MC group (Guggenbuhl et al. 2012). Plasma INO, the end product of phytate degradation, was increased (P < 0.05) in H2000, H3000, Q1000 and Q1500-fed pigs. Bone ash and breaking force in all phytase groups, except in Q500 group, were increased (P < 0.05) compared to the MC group.

Data from the present study showed similar effects for both enzymes. Phytases had beneficial effects on all measures, thereby compensating for reduced nutrient levels (Guggenbuhl et al. 2012). Increased plasma INO could be partly involved in the bone strength improvements (Croze and Soulage 2013). Nevertheless, the benefits of including high phytase dosages were limited in comparison to the low levels tested.

Table 1.  Mineral utilisation in weaned pigs fed graded amounts of two different phytases