PSVI-14 - Impact of phosphorus, calcium and microbial phytase on growth performance in growing pig; a meta-analysis

Abstract: The requirements for calcium (Ca) and phosphorus (P) differ for growth performance and bone mineralization. A mechanistic model has been developed to predict the requirement for maximum P and Ca deposition, so maximising both soft tissue and bone growth. However, literature showed that high Ca can reduces growth performance which is not considered in the model for the moment. The objective of this study was to quantify the effect of Ca, P and microbial phytase (PhytM) on average daily feed intake (ADFI), average daily gain (ADG) and gain to feed ratio (GF) and add these effects in the model to predict the requirements for growth and bone mineralization. A database built from 42 experiments, including 298 treatments was used in pigs from 35.6 to 59.1 kg BW. The random effect of the experiment has been included in the models. Multiples linear regression models has been fitted using Minitab software. The response of ADG to non-phytate P (NPP) is curvilinear (NPP and NPP x NPP, P < 0.001) while a tendency was found for a curvilinear effect for ADFI (P = 0.06) and GF (P = 0.08). Increasing dietary Ca reduced ADG (P < 0.001) and ADFI (P < 0.001) while GF was not modified. However, this effect is alleviated high NPP diet (Ca x NPP, P < 0.01). The response of growth performance to PhytM tended to be curvilinear for ADG and GF (PhytM x PhytM, P < 0.10). Adding 500 FTU/kg increased ADG by 5%. The effect of PhytM on ADFI depended on Ca (Ca x PhytM, P < 0.01); decreasing Ca increased the effect of PhytM with a 3% increased for 500 FTU in a 5 g Ca/kg diet. For GF the effect of PhytM depended on both Ca and NPP (Ca x NPP x PhytM, P < 0.01) with a PhytM effect of 15% for 500 FTU in a diet low in NPP (1 g/kg) and high Ca diet (8 g/kg). Results of the current meta-analysis showed P deficiency reduces growth performance, and that high Ca aggravated the deficiency mainly through reduced ADFI that induced ADG reduction without modifying GF. PhytM improved growth performance but the improvement is dependent of Ca and NPP levels for ADFI and GF. These results showed that at high NPP, i.e. close to requirement, Ca has no detrimental effect on growth performance. These equations will be implemented in the model predicting Ca and P requirement of pig.