Four experiments were conducted to evaluate the efficacy and safety of a microbial phytase (Novo SP938) in weanling and grower pigs, and starter turkeys fed corn-soybean meal based diets. Pig and turkey BW and pen feed consumption were recorded weekly. Fecal and excreta samples were collected for determination of Ca and P digestibility. At the end of all experiments animals were slaughtered, and 10th ribs or right foot for pigs, and both middle toes for turkeys were removed for bone analysis. In pigs performance, bone measurements, and digestibilities of P and Ca increased as levels of phytase increased. Concentration of P and Ca in the feces decreased as dietary phytase increased. In turkeys, BW gain and toe ash increased as nonphytate P or phytase increased, when added to a low-P diet. Concentrations of P and Ca decreased as phytase was added to the diet. Based on nonlinear or linear equations, the average P equivalency of 500 U phytase/kg feed was .64 and .67 g of inorganic P for pigs and turkeys, respectively. There were no adverse effects of feeding 10,000 U phytase/kg feed in pigs and turkeys. Supplementation with Novo SP938 phytase was effective in improving performance, bone mineralization, P and Ca utilization, and decreasing P and Ca concentrations in the feces of pigs and excreta of young turkeys fed low-P diets, with no health effects, even at very high supplementation rates. / Master of Science

Three studies were conducted. In the first study, 12 Yorkshire barrows (initial BW of 23.2 ± 2.0 kg) were allotted to 2 dietary treatments with 6 replications per treatment using a completely randomized design to determine apparent Ca and P digestibility (AD), true digestibility (TD) and endogenous output (EO) in a corn/SBM-based diet. All pigs were placed in individual feeder pens that allowed for easy collection of individual feces. The AD of Ca and P were 28.4% and 23.9%, respectively. Their TD of 42% and 40% for Ca and P respectively were significantly (P < 0.05) higher than the corresponding AD. EO was 0.8g for Ca and 1.3g for P per kg of dry matter intake (DMI). In the second study, the optimal dietary ratio of true digestible Ca and P was determined in terms of its effect on growing pig performance, excretion of Ca and P in feces and urine in a corn/SBM-based diet using a randomized complete block design. Thirty six growing barrows (initial BW: 24.2 ± 1.9 kg) were allotted to 6 dietary treatments with 6 replications per block. Six corn/SBM-based diets with very similar nutrient contents were formulated but differed in their dietary ratio of Ca to P. The balances of Ca and P and their true digestibility/retention were calculated for each diet. Animal performance and true retention of both Ca and P was optimal (P < 0.05) with diet 2 with a true digestible Ca to P ratio of 0.82: 1 compared to other experimental diets. The third study was conducted with a similar protocol to that used in experiment 1 involving 12 barrows (initial BW: 23.9 ± 1.1 kg) to determine Mg, Cu, Fe, Mn, Se and Zn TD values for the growing pig. Se and Zn AD of 73.9% and 9.5% significantly (P < 0.05) underestimated their TD of 82.1% and 15%, respectively. Se and Zn EO were 0.00004mg and 0.01 mg/kg of DMI, respectively. The TD and EO for Mg, Cu, Fe and Mn could not be estimated because of their negative AD.