The effects of phytase supplementation on nutrient digestibility, plasma parameters, performance and carcass traits of pigs fed diets based on low-phytate barley without inorganic phosphorus

A total of 80 crossbred pigs (25.5 +/- 2.6 kg) were assigned to one of eight dietary treatments. A positive control, based on Harrington barley, was formulated to meet requirements for total phosphorus. Three experimental diets (low in total phosphorus) were formulated based on either Harrington barley (0.28% phytate phosphorus) or the low phytate genotypes LP422 (0.14% phytate phosphorus) and LP 635 (0.09% phytate phosphorus). The four diets were fed with and without 1000 FTU kg(-1) phytase. Calcium and phosphorus digestibility were significantly higher (P < 0.05) as a result of supplementation with phytase. For the barley diets formulated without dicalcium phosphate, calcium digestibility averaged 69.6, 73.3 and 72.2% while phosphorus digestibility averaged 36.5, 50.5 and 57.7% for pigs fed the Harrington, LP 422 and LP 635 diets, respectively. The addition of phytase to the diet consistently reduced the percentage of phosphorus excreted in feces and fecal phosphorus excretion declined as the level of phytate in the barley declined. The addition of phytase tended to improve weight gain (P < 0.10) and significantly improved feed conversion (P < 0.05). For pigs fed the barley diets formulated without dicalcium phosphate, daily gain averaged 0.90, 0.99 and 1.01 kg d(-1) while feed conversion averaged 2.70, 2.39 and 2.38 for the Harrington, LP 422 and LP 635 diets, respectively. The overall results of this experiment indicate that the performance of pigs fed diets containing low-phytate barley formulated without a source of inorganic phosphorus is at least equal to that of pigs fed diets containing normal-phytate barley and inorganic phosphorus. In addition, the increased availability of organic phosphorus reduced the amount of phosphorus excreted thus reducing the amount of phosphorus that can potentially pollute the environment.