Effect of pelleting mixed feeds on phytase activity and the apparent absorbability of phosphorus and calcium in pigs

Abstract

Six diets were used to determine the apparent absorbability of phosphorus (P), using total faeces collection, in pigs from 40 to 100 kg live weight. In diets containing a considerable phytase activity from feedstuffs such as wheat, wheat middlings or barley, steam pelleting at ∼ 80°C sometimes decreased the P and calcium (Ca) absorbability by 10 percentage units or more. This was mainly due to a considerable reduction of the phytase activity. Cold-pelleting such diets had no negative effect on the P absorbability or phytase activity. In diets without phytase activity, steam pelleting had no negative effect on P and Ca absorbability. The results indicate, that when the temperature of the pellets reaches ∼ 80°C, the concentration of absorbable P can be decreased substantially in feeds containing a high phytase activity. The type of diet and the conditions during pelleting are therefore decisive in determining P and Ca absorbability.