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Latest Experience with Phytase in Poultry

Prof. Necmettin Ceylan and Prof. brahim Ciftçi Ankara University, Turkey

Phytate is a natural dietary content and constitutes 0.4–6.4% (w/w) of most cereals and legumes (Eeckhout and Deaepe, 1994). It is poorly digestible for monogastric animals due to a lack of effective endogenous phytase (Bitar and Reinhold, 1972). Phytate acts as an anti-nutritional factor, exerting its effects via a reduction in the solubility, and availability of phosphorus (P), and to a lesser extent, Ca, Zn, Fe (Nävert et al., 1985; Hallberg et al., 1987; Hurrell et al., 2003). It was also reported that phytate could decrease the utilization of protein, amino acids and starch. It has been suggested that phytate may bind with starch either directly, via hydrogen bonds, or indirectly, via proteins associated with starch (Thompson, 1988; Rickard and Thompson, 1997). Phytate is also known to inhibit a number of digestive enzymes such as pepsin, alpha-amylase (Deshpande and Cheryan, 1984) and increase mucin secretion, excretion of endogenous minerals and amino acids in broiler chickens (Liu et al., 2008). Another issue is higher cost of dietary inorganic P which has been increased remarkably in last decade because of shortened phospate sources. Poultry industry has still been growing and reached huge mass production and contribution to environmental pollution has been heightened concerns because of the poor utilization of phytate phosphorus by poultry.

As a solution of the problems related to phytate, the use of exogenous phytase in poultry diets has found widespread scientific and commercial acceptance to improve dietary phytate phosphorus (P) utilization and reduce the excretion of P in manure. Phytase was first detected in rice bran many decades ago (Suzuki et al., 1907) and then Warden and Schaible (1962) were rst to show that exogenous phytase enhances phytate-P utilisation and bone mineralization in broiler chicks. First commercial phytase was produced from Aspergillus niger and was released in market in 1991 (Selle and Ravindran, 2007). Phytases (myo-inositol hexakisphosphate phospho-hydrolases) are a large family of hydrolases capable of catalyzing the stepwise hydrolysis of myo-inositol hexakisdihydrogen phosphate (phytic acid; IP6). Feed-relevant phytases are divided into 2 subclasses; the 3-phytases such as those from Aspergillus niger initiate phytate degradation at the 3rd carbon position and 6-phytases such as those from Peniophora lycii, Escherichia coli and Aspergillus oryzae initiate phytate degradation from the 6th carbon position.

According to our current knowledge, since first phytase introduced commercially, efficacy of phytases depends on many factors including origin, pH optima, stability to heat and endogenous proteases, particle size and number of enzyme, any factor altering gastric pH, location of phytin within the seed and its chemical associations with other nutrients, Ca/P ratio, and also endogenous phytase activity of ingredients used in the poultry diets. So, great efforts have been made to discover more efficient phytase in each step of the development through years. There are now many commercial phytases from different origin and production technology that make serious contribution to poultry industry. However, efficacy and cost

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benefits of phytases differ significantly among commercial phytases, because different phytase enzymes have various characterizes based on sources from which they are derived so they don’t exert the same effect and activity in the digestive tract.

Research efforts in recent years have focused on the isolation and development of more efficacious phytase which overcome the above challenges. A series of experiments have been performed in broilers and layers by Çiftçi and Ceylan from Ankara University during last 2 years in which graded level of a novel microbial 6-phytase originated from Aspergillus oryzae was compared with inorganic P sources (DCP) and was also tested to other competitors. In broiler trials through 0-3 weeks graded level of the phytase including 500, 1000 and 2000 FYT/kg in the 1st experiment, and 500, 1000, 1500 and 2000 FYT/kg in 2nd experiment were compared to the graded level of inorganic P sources over negative control diets with 0.28% available P(aP) based on corn and soybean meal. In the first experiment, the novel phytase significantly improved the growth rate and feed conversion where the results of 1000 FYT/kg were found equal to 0.15 % additional aP from inorganic P. Excreted P via manure for 2000 FYT/kg phytase was reduced to 0.6% from 1.05% (43% reduction from positive control) and ileal P digestibility was increased by 55 and 26% (P<0.01) with 2000 FYT/kg compared to negative and positive control, respectively. 500 FYT improved ileal P digestibility by 32% (P<0.01) over negative control (0.28% aP) and equal to positive control (0.43% aP). In the second experiment, this trend was also continued and novel phytase supplementation resulted better growth (P<0.01) and feed conversion ratio (P<0.05) over the negative control (0.28% aP) and equal to the positive control. Manure P content was again significantly (P<0.01) reduced to 0.57% from 1.06% as positive control diet (0.28% aP) compared to 1500 FYT supplemented group. Ileal P digestibility was significantly improved to 61.8% from 50.3% by 1500 FYT compared to positive control. 500 FYT was found to be similar P digestibility with positive control, however 1000 and 1500 FYT/kg phytase supplementation had better P utilization over the positive control (P<0.01). In the third experiment, supplementations of 500, 1000 and 1500 FYT/kg phytase from Aspergillus oryzae were tested with un-supplemented negative control (0.28% aP) and positive control (0.43% aP) diets and also compared with 3 other commercial 6 phytases (2 of them originated from E.Coli, and one of them from Pichia pastoris). 500 FYT Phytase from Aspergillus oryzae had significantly better growth performance than negative control and was equal to positive control birds (P>0.05). 1000 and 1500 FYT/kg had additional improvements over positive control (P<0.01) and improved growth performance significantly (P<0.01). The ileal P digestibility results was interesting for tested phytases in which phytase from Aspergillus oryzae, 1500 FYT had the highest with 63.0% digestibility and the 500 FYT had 56.65% while the other three phytases at 500 FTU/kg had at least 6% lower P (P<0.01) digestibility with 48.64, 50.05 and 48.20% for Pichia pastoris and two E.Coli phytases, respectively.

In the layer trail (Ceylan and Çiftçi, 2012 unpublished yet) with Super Nick white hens, graded level of the novel 6 phytase (300, 450, 600 and 1000 FYT/kg) was tested against to P deficient negative control (0.14% aP) and to 4 increased level of aP from DCP (0.19, 0.24, 0.29 and 0.34% aP) in corn, soy and sunflower meal based diets. P deficient negative control diet caused significant reduction in overall performance parameters including livability.

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Phytase supplementation had increased the performance significantly to the peak level (P<0.01) recommended by producer of Super Nick. There was no significant differences (P>0.05) between inorganic P source and novel Phytase in egg mass, egg weight and feed conversion ratio, but overall survival rate was significantly higher in the phytase supplemented hens. Manure P content was significantly reduced and ileal P digestibility increased (P<0.01) by phytase. According to this long term layer trial, the novel 6 phytase has significant potential to improve performance and mineral status of the birds without using any inorganic P sources and reduce manure P content. Besides, 300 FYT is found well enough to keep the performance, but each increment in phytase activity still have response.

These series of experiments confirmed that the novel phytase have great potential to alleviate the anti-nutritional properties of phytate molecule for poultry and additional phytase over 500 FYT/kg up to 2000 FYT/kg still continue to breakdown the phytate.

Additional improvements in growth performance over bone development in our researches can be attributed to the complete breakdown of phytate and removing it’s anti nutritional properties on other nutrients. Liu and Ru (2010) reported that microbial phytase could improve amino acids utilization by decreasing their endogenous losses in the intestine of broiler chickens. Aureli et al.,(2013) showed modified intestinal morphology with phytase, by resulting in longer jejunal (P<0.001) and ileal villi and wider villi in the duodenum (+27%) and jejunum (+25%) compared to NC. It seems that phytase supplementation does not only help the hydrolysis of phytate-P but also have a significant modification on the intestinal tract, even more so in the proximal parts, which could help increase absorption.

We can conclude that efficacy of commercially available phytases in same activity do not give equal improvements in birds. Benefits and contribution of novel phytases is beyond improvement P digestibility which can be explained by effective breakdown of phytate molecule than previous phytase generation. It must be also considered that using this kind of novel enzymes would cause significant changes in dietary strategies and establishments of poultry nutrient requirements. We think that the poultry industry has now a very powerful tool to feed animals and protect the environment.