Dietary phytate, calcium and phytase levels affect growth performance in weaned pigs

Phytase addition to swine diets improves mineral utilisation and bone strength with less consistent effects on performance (Selle and Ravindran 2008). The aim of this study was to evaluate the effects on performance in weaned pigs fed diets with different levels of phytate (phy), calcium (Ca) and phytase (C. braakii; Ronozyme HiPhos, DSM). The hypothesis tested was that the phytase (R) concentration would modulate weaned pig performance in the presence of different dietary levels of phy and Ca.

An experiment was conducted with 128 28-day-old castrated male weaned pigs (Large White × Redon) having an initial bodyweight of 7.2 ± 1.2 kg (mean ± s.e.). Pigs were randomly allotted into eight treatment groups of 16 animals each (four pens of four piglets). They were fed ad libitum for 42 days with mash diets based on corn, soybean meal and rapeseed meal. Eight diets were formulated to meet the animal requirements for weaned pigs according to NRC (2012) (crude protein (CP), 198 g/kg; metabolisable energy (ME), 13.0 MJ/kg; total P, 0.47%; total lysine, 1.40%). The experiment was conducted in a 2 × 2 × 2 factorial design with two dietary phy (0.18 and 0.31%), Ca (0.45 and 0.80%) and R (1000 and 2500 FTU/kg) concentrations. Growth performance parameters were recorded throughout the study and average daily gain (ADWG), average daily feed intake (ADFI) and feed conversion ratio (FCR) were calculated. Data were analysed as a 2 × 2 × 2 factorial ANOVA and differences between groups were determined by the Student–Newman–Keuls multiple-range test (significant at P ≤ 0.05) (StatGraphics Centurion XVII, Manugistics, Rockville, MD, USA).

High dietary phy had a positive effect (P < 0.05) on ADWG and FCR for the first period (d 0 to 14) and overall period (d 0 to 42), but increasing (P < 0.05) the ADFI for these periods (Table 1). By contrast, high dietary Ca had a negative impact (P < 0.05) in all periods on ADWG and FCR (Table 1). High dietary Ca inclusions are well documented to significantly reduce the overall impact of phytase (Selle et al. 2009). Indeed, the ability of Ca to bound to phy reduced the potency of phytase to produce digestible P by degrading phy and by that impacted the performance of the weaned piglets (Kim et al. 2017). Furthermore, the high Ca concentrations affected less ADFI, indicating that the reduced ADWG may be due to less available P coming from phy.

Table 1.  Growth performance in weaned pigs fed different levels of Ca, Phy and R

Data from the present study showed that high dietary phytase could not modulate the performance of weaned pigs fed a diet containing a high amount of Ca.