Change of the apparent digestibility of nutrients and phosphorus as a function of phosphorus source and phytase supplementation in pigs

摘要

The objective of the experiment was to examine the effect of phytase addition on absorption and apparent digestibility of P when a maize-soyabean meal-based diet was supplemented by different levels of inorganic phosphate. An isotope (P-32) metabolic experiment was carried out on crossbred barrows (initial BW of 15-18 kg). The dietary treatments were arranged in a 2 x 2 factorial design with two levels of total P (A:0.67 and L:0.59%) having different levels of P bioavailability (A:0.36 and L 0.28%), and two levels of microbial phytase (0 and 500 FTU/kg of diet). In phase I the pigs in groups 1/a and 1/b were fed diets with two levels of P (A and L) without phytase. In phase 2, these pigs were fed diets of A and L with enzyme supplementation (groups 2/a and 2/b). The apparent digestibility of nutrients was unaffected by phytase. Pigs fed diet L had decreased organic matter- and ether extract digestibility. In group 1/a the piglets digested 52.3% of the total P and a similar value was found in group 1/b. As the result of phytase supplementation, the digestibility of the total P increased by 7% in group 2/a and 23% in group 2/b. The digestibility of P originating from inorganic P supplementation (monocalcium phosphate) decreased by 11 and 4% in groups 2/a and 2/b, respectively. The apparent digestibility of phytate P was not affected in the animals fed the diet without enzyme supplementation (1/a and 1/b). However, phytase enhanced the apparent digestibility of phytate P from 31.6 to 43.9% and from 35.8 to 54.5% in pigs fed diet 2/a and 2/b, respectively. These results show that faecal excretion of inorganic P increases and absorption of phytate-P improves by the action of phytase. In summary, the amount of inorganic P supplementation can be decreased and it is environmentally advantageous to replace inorganic P with microbial phyrase.