دانلود رایگان ترجمه مقاله برآورد فیتاز میکروبی در رژیم های غذایی جوجه های گوشتی (نشریه Oxford Journals 2004)

ارزیابی فیتاز میکروبی در رژیم غذایی جوجه های گوشتی

Evaluation of Microbial Phytase in Broiler Diets

Abstract

Two trials were conducted to evaluate the efficacy of a new microbial phytase (Phyzyme XP) for broiler chicks. Trial 1 used 192 8-d-old male broilers in a 14-d trial to assess growth and nutrient utilization. Dietary treatments (221.9 g/kg CP) included a positive control [5.0 g/kg nonphytate P (NPP)], negative control (1.2 g/kg NPP), and negative control plus 500 or 1,000 phytase units/kg of diet. Phytase addition increased weight gain, feed intake, feed efficiency, and tibia and toe ash (linear, P < 0.01) with tibia ash also responding quadratically (P < 0.05). Apparent ileal digestibility of P (linear and quadratic, P < 0.05), tryptophan, and valine (linear, P < 0.05) also increased. Linear and quadratic responses were observed for retention of DM, nitrogen, P, and several amino acids (P < 0.05) with added phytase. Trial 2 utilized 576 1-d-old male broilers over a 42-d period to evaluate growth performance. Diets were formulated for starter (222.7 g/kg CP) and grower (201.5 g/kg CP) phases and included a positive control (starter and grower, 5.0 and 3.8 g/kg NPP, respectively); negative control (starter and grower, 2.4 and 1.8 g/kg NPP, respectively); negative control plus 500, 750, or 1,000 phytase units/kg; and negative control plus 500 phytase units/kg of Natuphos phytase. Phytase increased weight gain and feed intake (starter, grower, overall) as well as feed efficiency during the starter period (linear, P < 0.05). Feed intake was also improved during the grower period and overall (quadratic, P < 0.05). Tibia and toe ash of birds fed for the first 21 d increased (linear, P < 0.05) with tibia ash also increasing quadratically (P < 0.05). Overall, tibia and toe ash were improved due to phytase addition (linear and quadratic, P < 0.05). In conclusion, this microbial phytase, derived from Escherichia coli and expressed in Schizosaccaromyces pombe, elicited improved growth performance, bone mineralization, and P utilization in broiler chicks.

1 Introduction

A significant portion of the P in mature cereal grains and oilseeds is present as phytate P as this is the main storage form of plant P and inositol (Erdman, 1979; Maga, 1982). Nonruminant animals have insufficient phytase to effectively digest phytate (Nelson, 1971), hence inorganic P is often added to their diets. The excretion of P in animal manure has received the greatest attention as potential environmental pollutants of agricultural origin. Phosphates are not highly soluble in water but accumulate in soils that may eventually result in runoff and, along with N, lead to eutrophication of surface waters, a condition that is detrimental to aquatic animals. The poor digestive utilization of phytic acid P by monogastric animals and its consequences on diet cost, environment, and digestibility of minerals and proteins have led to extensive research efforts directed toward improving phytate digestion. Re- search has demonstrated definitively that phytase has merit as a tool for minimizing P excretion by increasing P availability and subsequent utilization (Ravindran et al., 1995a). The currently available feed-grade phytase products have room for improvement in efficacy. The search for novel phytase preparations, with relatively greater potency in intestinal phytate hydrolysis and better heat stability, is an ongoing process. In accordance with this goal, the objective of this study was to evaluate the efficacy of a microbial phytase on growth performance and nutrient utilization when fed to broiler chicks in cornsoy based diets.