| The use of low protein and a new phytase enzyme were studied in swine diets, as nutritional strategies to improve the efficiency in the use of nitrogen and phosphorus, and also to reduce NH3 production and odor offensiveness from pig production, while producing environmentally friendly manure. The effect of reducing dietary crude protein (CP) in growing pigs was evaluated in two independent experiments, using either an adequate or a reduced CP level (19 or 14%). The first study measured the amount of N loss as aerial NH3 and odor offensiveness in the air from growing pigs confined in dynamic airflow chambers, and the second study evaluated the same diets using N balance techniques. Reducing dietary CP did not affect (P > 0.05) growth performance, but decreased slurry pH (P < 0.09) from 6.71 to 6.21 +/- 0.186. Reducing CP decreased (P < 0.001) urinary N excretion by 56% and total N excretion by 41%. Overall, for every one percentage unit reduction in dietary CP (combined with AA supplementation) there were reductions in total N losses (fecal plus urinary) by 8%, and ammonia production by 15%, but no change in odor intensity. To compare the effectiveness of 2 phytase enzymes (Phyzyme and Natuphos), growth performance, fibula ash, and Ca and P digestibilities were evaluated in 4 studies. The first 3 studies (N = 832 pigs) used graded level of the enzymes in P-deficient diets for nursery, grower and finisher pigs. Overall growth performance (ADG and Gain:Feed) and bone ash improved linearly with phytase addition, G:F was, 5% greater (P < 0.05) with Phyzyme than with Natuphos. The fourth study showed that aP increased (P < 0.001) by 0.17 and 0.06 g (+/- 0.023) per 100 FTU consumed for Phyzyme and Natuphos, respectively. Phyzyme proved to be effective in releasing phytate bound P from diets, with an efficacy superior to a commercially available enzyme. It is concluded that the use of low protein diets and the use of phytase enzymes are relevant strategies that increase the efficiency in the use of N and P and also, reduce the excretion of these nutrients to the environment. |
