Influence of phosphorus level and soaking of food on phosphorus availability and performance in growing-finishing pigs

Abstract

AbstrctThe effects of 1-h soaking of a pig diet based on wheat and barley with low (4·1 g P per kg) and high (6·8 g P per kg) total phosphorus (P) content on total tract apparent digestibility and performance in growing-finishing pigs were studied in a balance and a performance trial respectively. Phosphorus bound to inositol penta- and hexaphosphate (IP5-IP6) was reduced by proportionately 0·1 in the soaked food. Soaking numerically increased the apparent digestibility of P. The digestibility of P did not differ between the dry high P and the soaked low P. Excretion of P in urine was correlated (R2= 0·84) with the intake of digestible P. The average daily weight gain, final body weight and carcass weight were lower (P< 0·001), and the energy conversion ratio was higher (P< 0·001) in the dry low P treatment than in the other treatments. Pigs on the low P diets had lower levels of inorganic P in serum (P< 0·01) and slightly higher serum Ca values (P< 0·05) and there were no effects of soaking. The density of femur was lower (P< 0·01) in both the low P treatments than in the high P treatments, and soaking of the low P diet improved (P< 0·01) femur density. In conclusion, a 1-h soaking of pig food in water appears to be sufficient to improve P availability and growth performance.