Wageningen UR Livestock Research determined the influence of phosphorus (P) content in the feed on growth performance, feed utilisation, phosphorus retention and bone quality in growing sows and boars from 25 to 125 kg. The present recommendations are adequate for animal performance but a higher dietary P content further enhances P retention and bone quality. At a dietary P content commonly used in practical diets, P utilisation and retention in boars is similar to sows. Hence, the present standard value for whole body P-content is adequate for both sows and boars. This study was commissioned and financed by the Dutch Ministry of Economic Affairs and the Dutch product boards for Animal Feed and Livestock and Meat.
Importance of efficient use of phosphorus resources
For optimal use of limited resources of P and to minimise P excretion in the manure, insight in the effect of P in the diet on performance and bone strength of the pigs and P retention in the body is required. Phosphorus is an essential nutrient for all farm animal species and mainly retained in the skeleton and muscle tissue. An adequate P content in the diet is needed for growth performance and health of the pigs. The whole body P content is used to calculate efficiency of P-utilisation on pigs farms.
Different levels of phosphorus in diets studied
In this study we supplied male and female pigs with increasing dietary P levels from 50 to 130% of the present recommendations and determined growth performance, feed conversion and P retention in the body between 25 and 125 kg body weight.
Present recommendations adequate for growth
In general this study indicates that present recommendations are adequate to maximize animal performance. A dietary P content below requirements resulted in a lower daily gain and a less efficient feed utilisation. However, the P-retention in the body and the metacarpus bone ash content increased linearly to the highest diet P content of 130% of recommendations.
Extra phosphorus enhances bone ash
For future application, we will need to define what level of bone ash is desirable in order to estimate what dietary P content is required. At low P levels the pigs give priority to muscle and lean tissue deposition above skeleton development. Consequently, growth performance is maximised at lower dietary P-levels at the expense of P-retention in the skeleton, bone ash content and bone strength.
Phosphorus content similar in boars and sows
Boars realised a higher gain and more efficient feed utilisation than sows and had less lipid and more protein in their bodies. Boars did not show a higher whole body P content. Rather, at low dietary P level, body P-content was higher in sows. Hence, our results indicate that efficiency of P utilisation in pig farms can be based on the same standard whole body P-content for boars and sows.