The effect of dietary phytase supplementation on the N-balance of growing pigs

Some studies suggest that dietary phytase enhance the growth rate of pigs fed P-adequate diets. This may be due to an increased N digestibility and/or improved protein gain. The aim was to study the effect of dietary phytase supplementation on the N-balance of growing pigs upon protein limiting condition. A total of 24 hybrid individually kept barrows (25kg BW) were assigned into 4 treatments. Diet in APO (AP: adequate protein) contained 190g/kg crude protein and no phytase supplementation, diets in RP0, RP500 and RP1000 (RP: reduced protein) contained 160g/kg crude protein and 0, 500 and 1000 FTU/kg phytase supplementation, respectively. The balance trial consisted of 7 days adaptation and 5 days collection, during which the feces and urine were collected quantitatively. Additional phytase to low protein diets increased the N-retention of the pigs (P<0.05). Supplementation of 500 FTU/kg (PR500) resulted similar N-retention as in group APO (P>0.05). Dietary treatments did not affect the digestibility of protein, however, 500 FTU/kg phytase supplementation increased the efficiency of N-retention. Our results show that the protein content of the feed for pigs of 20-30kg can be reduced from 190 to 160 g/kg if the diet is supplemented with 500 FTU/kg phytase without weakening the N-balance of pigs.