This experiment was carried out to evaluate the effects of the inclusion of different levels of phytase on broiler performance, bone densitometry, and phosphorus and nitrogen excretion. Nine hundred and sixty one-day old broilers, 50% males and 50% females, were distributed in a completely randomized experimental design into five treatments and six replicates 32 birds each. The treatments consisted of a control diet and four diets with the addition 25, 50, 75, and 100 g/ ton of phytase (250, 500, 750 and 1000 FTU of phytase/kg fed). Diets were formulated to contain equal nutritional levels, and considered the phytase product nutritional levels. In general, the addition of phytase resulted in a linear decrease in broiler performance. However, the performance results obtained with the level of 250 FTU phytase/kg feed were not different from the control treatment. The best bone density results were observed in the control treatment, with no phytase. The results of this experiment indicate that the nutritional matrix of the phytase product needs to be reviewed when added in levels higher 250 FTU/kg to broiler diets.
INTRODUCTIONAiming at lowering production costs, many current research studies have focused on improving the efficiency of feedstuff utilization and to reduce the impact of animal production on the environment (Payne et al., 2005).Phosphorus is one of the most expensive nutrient of poultry and swine feeds, second only to energy and protein (Borges, 1997). It is nutritionally essential, as shown by its several roles in the body, and it is particularly important during growth. However, two thirds of the phosphorus contained in cereal grains and oil seeds are in the form of phytate, which can bind to other nutrients, rendering them unavailable for poultry and pigs, thereby, requiring dietary inorganic phosphorus supplementation (Denbow et al., 1995).The production of industrial phytase is based on microorganisms, using DNA recombination techniques. This enzyme increases phosphorus (P) availability in plant feed ingredients, where P is usually present as phytate. The dietary supplementation of phytase allows poultry and pigs to more efficiently absorb phosphorus, reducing the amount of inorganic phosphorus supplementation, and promoting better weight gain, feed conversion ratio, feed intake, and bone mineralization, as well as reducing mortality (Qian et al., 1996).Along with calcium, phosphorus has an essential role in bone formation. In the animal, phosphorus comprises about 1% of live weight, and it is carefully considered when feeds and supplements are formulated. About 80% of phosphorus in the animal body is deposited
26in bones and teeth. Therefore, the inclusion of phytase in broiler diets may enhance their bone development. The objectives of the present study were to evaluate the effects of the inclusion of different levels of phytase on broiler performance, bone densitometry, and phosphorus and nitrogen excretion in the litter during the starter (1 to 21 days), grower (22 to 42 days), and t...
