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Significance of Phytase as a Dietary Supplement

15 February 2008

By Chris Harris Senior Editor ThePoultrySite. The significance of phytase as a supplement to the diet of both broiler chicken and laying hens was one of the central themes in presentations to the recent International Poultry Scientific Forum in Atlanta, Georgia. During a series of presentations, research covering how added phytase reacts with the phytase already within the feed mix and pelleted feed, how it reacts in both simple and complex feeds and how different commercial phytase products perform.

Influence of endogenous phytase activity on exogenous phytase pellet stability evaluation

A large proportion of monogastric feed is enriched with microbially derived phytases to improve the digestibility of phosphorus.

Phytate is the major phosphorus source in wheat and corn, and approximately 75 per cent of all phosphorus in the grains is bound within phytate molecules. According to S. Dalsgaard in his paper on the Influence of endogenous phytase activity on exogenous phytase pellet stability evaluation phytate cannot be degraded by the animal itself, and the animal needs exogenous phytase to degrade the phytate in vivo.

The research by Dr Dalsgaard, F.Isaksen and T. Gravesen from Genecor, Danisco in Denmark and M.Hruby from Danisco Animal Health in St Louis, Missouri, the exogenous phytase pellet stability is an important topic for the feed industry.

The primary way of evaluating exogenous phytase thermostability is by running pelleting tests in commercial feed mills. However, endogenous phytase from the raw materials can influence the outcome of the test results. The endogenous phytase originates mainly from wheat or wheat by-products, which are, in many markets, ingredients used at high levels in animal feed.

The presence of endogenous phytase can then cause an incorrect interpretation of thermostable phytase product thermostability. The evaluation dealt with two aspects of how endogenous phytase influences the outcome of pelleting trials. First, a commercial pelleting trial, where the endogenous phytase is inactivated at 90°C and second, a test of endogenous phytase thermostability over a temperature range of 75°C to 95°C.

The results show 85 per cent inactivation of the original endogenous phytase activity at 95°C.

The overall conclusion is that the endogenous phytase is not thermostable. However, it is present and active in mash feed before pelleting and if the recovery of added (exogenous) phytase product is calculated based on the activity in mash feed, the recovery and thereby the thermostability of the added phytase can be underestimated.

Evaluation of heat stable phytases in pelleted diets fed to broilers from day 0 to 35

While the thermostability of added phytase might be questioned, the addition of a heat stable phytase to pelleted feed can improve leg condition in broilers.

J. R. Timmons told the Poultry Scientific Forum that broiler rations are typically pelleted to promote improved broiler performance.

Before advent of heat stable phytase product forms, phytases (Ph) were generally added post-pelleting to prevent Ph inactivation from high pelleting temperatures.

The aim of the study by Timmons and R. Angel from University of Maryland, College Park, J. M. Harter-Dennis from University of Maryland Eastern Shore, Princess Anne, W. Saylor from University of Delaware, Newark and N. Ward from DSM, Parsippany, NY, was to evaluate retained Ph activity of two heat stable phytase enzymes (PhA and PhB) in pelleted diets fed to 0-35day old straight run Ross 708 broilers.

Phytase diets were deficient in non-phytate phosphorus (NPP) (0.28, 0.185, and 0.11 per cent NPP, starter (S), grower (G), and finisher (F) diets, respectively) and all treatments (TRT) were pelleted at 93.3 °C.

A RCB design was used and per cent retained Ph activity (RPhA), weight gain (WG), feed efficiency (F/G), and percentage tibia ash (TA) were measured. TRT included a positive control (PC) (0.45, 0.40, 0.35 per cent NPP, in S, G, F diets, respectively), negative control (NC) (0.35, 0.25, 0.16 per cent NPP in S, G, F diets, respectively), 0.5XPhA, 1XPhA, 2XPhA, 0.5XPhB, 1XPhB, and 2XPhB (TRT 1-8, respectively).

Manufacturer recommended enzyme level was 1X. RPhA (averaged over 3 diet phases) was not different (P=0.07, SEM 4.15) between TRT 3-8 (64.3, 69.8, 80.0, 81.0, 73.2, and 69.5 per cent, respectively) suggesting heat stability of both PhA and PhB are similar. No differences (P>0.05) between TRT were detected in WG (average 659.2; d21 and 1,618.5 g; d35). F/G of 35 d old birds fed TRT 5-7 was three per cent lower (P=0.05) than F/G of birds fed NC. Differences were detected in TA at d 21 and 35. Day 21 TA of TRT 1 (51.0 per cent) was higher (P=0.05) than TA of TRT 2-8. However, no differences (P>0.05) were detected in TA of birds fed 1XPhA and 1XPhB (49.4 and 49.1 per cent, respectively). Day 35 TA values were 50.51a, 47.95c, 48.90bc, 48.95bc, 49.60ab, 48.87bc, 49.51ab, and 50.10 per cent ab for TRT 1-8, respectively. TA of birds fed the PC diet was five per cent higher (P=0.05) than TA of birds fed the NC diet. However, TA of birds fed TRT 2XPhA, 2XPhB, and 1XPhB were not different (P>0.05) than the TA of birds fed the PC diet, and no differences in TA were detected between any Ph TRT. Results suggest that supplementing NPP deficient diets with a pre-pelleting HS Ph will improve TA of birds fed pelleted diets.

Impact of a bacterial phytase on broiler chickens when fed simple or complex diets.

A study into one bacterial phytase product to reduce the negative influences of dietary phytate was conducted by T. M. Parr, R. Upton, C. L. Wyatt, from Syngenta Animal Nutrition, Research Triangle Park, in North Carolina and S. W. Davis from Colorado Quality Research, Wellington, Colorado.

An evolved, thermo-tolerant bacterial phytase (Quantum Phytase™; QP) has been evaluated in many broiler studies which utilized diets typically composed of a commercial corn-soya-animal protein base.

Dr Parr said that with increasing ingredient prices, more non-traditional feedstuffs are being considered so the objective of the study, Impact of a bacterial phytase on broiler chickens when fed simple or complex diets was to compare the response of feeding QP to broilers in a simple corn-soya, semi-complex or a complex diet (containing corn, soybean meal, canola meal, rice bran and sunflower meal).

The phytate content in the corn-soya averaged 0.23 per cent whereas the phytate levels increased in the complex diet (average 0.38 per cent).

For each of the diets AvP, Ca, ME and aa were lowered to result in a negative control (NC) which matched the positive control (PC).

Phytase was added to the NC diets at 200 or 300g/mt (equivalent to 500 or 750FTU/kg, respectively) and fed as pellets for 42 days. Body weight, feed intake, FCR and mortality were recorded over the trial period.

At 42 days, left tibias were collected for bone ash analysis.

The addition of phytase at either inclusion level improved body weight and bone ash in broilers fed NC diets achieving performance equivalent to the positive control group. Increasing dietary phytate levels by including non- traditional feedstuffs negatively impacted performance within the NC groups only.

The study showed the ability of QP to effectively reduce the negative effects of dietary phytate regardless of diet complexity.

Evaluation of a bacterial phytase on nutrient metabolism and performance in broiler chickens

Another study by Wyatt, Upton, Parr, and W. Rieping from Syngenta Animal Nutrition investigated the optimum nutrient digestibility and phosphorous retention for Quantum Phytase.

The researchers told the Scientific Forum that previous research clearly demonstrated that the addition of a phytase liberates phytate-bound phosphorus in poultry diets.

However, the researchers said that discussion still remains on the effects of phytate, and ultimately a phytase, on energy and nitrogen retention.

The objective of the experiment was to evaluate the inclusion of a bacterial phytase (Quantum Phytase; QP) on bird performance from 1-40 days and on nutrient metabolism.

The trial was carried out on broilers on a Brazilian broiler farm.

A total of 1250 male, Ross broiler chicks were randomly distributed among five treatments. There were 10 replicates per treatment, in floor pens containing 25 chicks per pen.

There were two negative controls where phosphorous and calcium were removed and the test checked the feed conversion and consumption rates.

There were three basal diets consisting of a positive control (PC); a negative control (NC1) formulated to contain a nutrient reduction of 0.12 per cent average P, 0.077 per cent Ca, 0.003 per cent Lys, 26 kcal ME, 0.12 per cent protein and a negative control 2 (NC2) formulated to contain a nutrient reduction of 0.13 per cent average P, 0.10 per cent Ca, 0.01 per cent Lys, 45 kcal ME, 0.36 per cent protein.

Quantum Phytase was added at 100g/mt (equivalent to 250FTU/kg) to NC1 and 200g/mt (equivalent to 500FTU/kg) to NC2. Supplementing Quantum Phytase in NC1 and NC2 diets returned BW, FI, and FCR in broilers to equal that of the PC-fed birds. At day 19-23 ileal samples were collected from broilers to determine nutrient digestibility values.

Feeding Quantum Phytase significantly improved the energy values of 30 and 57 kcal DM/kg, respectively for the NC1 and NC2 diets. Quantum Phytase increased ileal digestibility of phosphorus and retained phosphorus (mg/b/d).

Thus, excreted phosphorus was reduced and phosphorus deposition was improved in tibia ash content, especially for birds fed NC2 containing 200g/mt Quantum Phytase.

The inclusion of Quantum Phytase at 200g/mt showed the best results for nutrient digestibility, phosphorus retention, and lower phosphorus excretion and similar performance and tibia composition to the positive control. The test also showed that when phosphorous was taken out of the diet feed consumption went down and body weights reduced. By supplementing the diet with phytase, body weights returned.

February 2008



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