The objective of the present study was to assess the effect of phytase supplementation of sorghum-canola meal diets without added inorganic phosphorus (iP) on growth performance, apparent total-tract P, calcium (Ca), nitrogen (N), and energy utilization, bone strength, bone ash and serum Ca and P concentrations. For that purpose, two experiments were carried out. For the first trial, 42 crossbred barrows were fed in individual metabolism cages a P-deficient diet for 7 d before starting a 28-d experiment. This trial consisted on 7 treatments that were a negative control (NC) diet supplemented with 0, 400, 800, 1200, or 1600 U of Aspergillus niger (AN) phytase/kg, a positive control (PC) diet, and the PC diet supplemented with 1200 U of AN phytase/kg. Fecal and urine collections were made from d 21–26, and blood samples were collected on d 0, 14, and 28. For the second trial, 126 growing-finishing crossbred pigs with an initial BW of 21.6 kg were group-fed (3 pigs/pen) in 3 phases (grower, early-finisher, and late-finisher). The second trial consisted on 6 treatments that were a NC diet for each phase supplemented with 0, 200, 400, 600, or 800 U of AN phytase/kg and a PC diet. Fecal collections were made from d 49–54 and blood was collected on d 35, 63, and 91.
In both trials, 400 U of AN phytase/kg of diet was satisfactory for growth performance compared with the PC treatment groups. On the first trial, apparent total-tract P absorption and retention plateaued at 1200 U of AN phytase/kg of diet, with a reduction on fecal Ca and P of 22.4% and 28.6%, respectively, compared with the PC treatment group. Pigs fed the PC + 1200 U of AN phytase/kg absorbed and retained more P (g/d) than any other treatment group. On the second trial, apparent total-tract P absorption, bone strength and bone ash weight plateaued at 600 U of AN phytase/kg of diet, with fecal P excretion reduced 29.4% compared with the PC treatment group.
In both trials, the AN phytase treatments did not increase Ca, N, or energy absorption (amount/d or % of intake) and had no effect on serum Ca and P concentrations.
Veum, T.L. and Liu, J. 2018. The effect of microbial phytase supplementation of sorghum-canola meal diets with no added inorganic phosphorus on growth performance, apparent total-tract phosphorus, calcium, nitrogen and energy utilization, bone measurements, and serum variables of growing and finishing swine. Livestock Science. https://doi.org/10.1016/j.livsci.2018.05.017