A Dose Response of a Heat Stable Phytase on Broiler Performance and Nutrient Digestibility

Published: January 9, 2023

By: L. NOLLET 1, R. SERWATA 1, T. WIBOWO 2 and F. POERNAMA 2 / 1 Huvepharma NV, Belgium; 2 PT JAPFA COMFEED Indonesia.

Summary

A total of 2160 male broilers were distributed over 60 pens to host 5 treatments. A starter feed (day 1 to 21) and finisher feed (day 22-35) were used (both pelleted). A negative control (NC) feed was reformulated by reducing a positive control (PC) feed by 0.2 percentage point protein, 0.02 percentage point dig. Lys (and other essential amino acids keeping a constant ratio to Lys), 0.18 percentage point Ca and P, and 0.09 MJ/kg ME. The PC starter feed contained 202 g/kg crude protein (CP), 11.5 g/kg dig Lys, 12.04 MJ/kg ME broiler, 8.0 g/kg Ca, 6.8 g/kg P, and 4.0 g/kg available P (aP). The PC finisher feed contained 176 g/kg CP, 9.5 g/kg dig. Lys, 12.67 MJ/kg ME broiler, 7.0 g/kg Ca, 5.9 g/kg P and 3.4 g/kg aP. To the NC feeds 0, 250, 500 or 1000 FTU of phytase was added per kg of feed and performance was measured per feeding phase. At 21 days, bone ash was determined on 3 birds per pen. At the end of the trial, 10 birds per pen were killed and ileal samples was collected to determine P, Ca and CP in order to calculate their digestibility.

Results indicated that the phytase at 250 FTU/kg could compensate for the performance loss due to the feeding the NC, bringing body weight back to the PC level (2445 g/b vs 2428 g/b and 2396 g/b for 250 FTU/kg for the PC and the NC, respectively). The final body weight reached 2447 g/b and 2518 g/b for the 500 FTU and 1000 FTU/kg treatments. Feed conversion (FCR) was significantly increased in the NC (1.600 vs 1.572 for the PC; P < 0.05) while the FCR was 1.575 and 1.580 for the 250 FTU/kg and 500 FTU/kg treatment (not significant versus the PC nor NC). The FCR at a dose of 1000 FTU/kg (1.572) was significantly different from the NC (P< 0.05). Bone ash increased in a dose responsive way whereby the 1000 FTU/kg treatment reached nearly the value of the bone ash of the PC (39.2 % vs 39.7 % respectively).

The digestibility of P increased linearly with increasing levels of phytase addition (71.3, 76.9 and 78.4 % for 250, 500 and 1000 FTU/kg versus 46.3 and 48.7 % for the PC and the NC respectively). This effect was significant for all phytase vs PC and NC while the 1000 FTU/kg treatment was also significantly different from the 250 FTU/kg treatment (P < 0.05). Crude protein digestibility increased with phytase addition, however no significant differences between treatments could be detected (73.3, 73.4, 75.5, 76.4 and 76.3 % for PC, NC, 250 FTU/kg, 500 FTU/kg and 1000 FTU/kg, respectively). Ca digestibility was significantly higher for the NC and the phytase supplemented feeds (30.6, 48.2, 49.8, 50.5 and 54.3 %, respectively). Based on the digestibility values and the P, Ca and CP levels in the feed, it was calculated that the phytase at 250, 500 and 1000 FTU/kg resulted in improvements of 1.11, 1.38 and 1.45 g/kg dig P, of 3.95, 5.67 and 5.49 g/kg digestible protein and of 0.11, 0.15 and 0.40 % dig. Ca per kg feed respectively.

I. INTRODUCTION

Phytases have been heavily researched for decades and been used commercially since the early 1990s). Phytase from microbial origin is therefore added to monogastric diets as it can reduce the incorporation of inorganic P sources in the feed, reducing feed cost and P excretion in the environment. Phytate is the main storage form of phosphate in plant matter and in vegetable feed ingredients where it can normally be found in concentrations of 5 to 25 g/kg (CVB, 2018).

Phytate has anti-nutritive effects in poultry because it binds phosphorous and other nutrients and decreases their availability (Beeson et al., 2017). Therefore, phytase can also lead to improved animal performance. The aim of this trials was to evaluate the effect of a novel, intrinsic heat stable phytase on animal performance and nutrient digestibility.

II. MATERIAL AND METHODS

A total of 2160 male broilers (DOC MB202 Platinum) were distributed over 60 pens (12 pens per treatment and 36 broilers per pen) for 35 days. A starter feed (day 1 to 21) and finisher feed (day 22-35) were used (both pelleted). A positive control feed was formulated to meet all animal requirements including P and Ca. A negative control (NC) feed was reformulated to reduce this positive control (PC) by 2 g/kg protein, 0.2 g/kg dig. lys, 1.8 g/kg Ca and available P (aP), and 0.09 MJ/kg ME (Table 1). The reduction in dig. lysine was applied to all other essential amino acids in order to maintain the same ratio to lysine as in the PC.

Table 1 - Feed composition and calculated composition for starter and finisher (g/kg)

The NC was supplemented with a novel, intrinsic thermostable phytase (OptiPhos® Plus, Huvepharma) to reach 0, 250, 500 and 1000 FTU/kg of feed. To all feed an NSPase (Hostazym® X, Huvepharma) was added. The finisher feed contained TiO₂ as a marker at 4 g/kg.

Body weight gain, daily growth rate, feed intake and feed conversion were determined for every feeding phase. Bone ash was determined on a pooled sample of 3 birds per pen. The bones were dried overnight at 100ºC, defatted in ether for 6 h, and burnt to ash in a muffle furnace. At the end of the trial, 10 birds per replicate were euthanised and ileal samples was collected according to the methodology of Shastak et al. (2012). Total P, Ca, CP and TiO₂ were analysed in order to calculate their digestibility using TiO₂ as digestibility marker. Phytase was analysed in all feeds by ISO30024 (2009) to verify good incorporation.

III. RESULT AND DISCUSSION

Phytase levels detected in the phytase supplemented feed were in line with the aimed doses (260, 510 and 875 FTU/kg for starter and 270, 670 and 1010 FTU/kg in finisher for 250, 500 and 1000 FTU/kg respectively). Phytase levels in all PC and NC feeds were not detectable (< 50 FTU/kg).

Despite the reduction in nutrients, in particular the strong reduction in Ca and P level, there was only a limited effect on end weight (2396 vs 2428 g for the NC and the PC respectively), and a small, but statistically significant, effect on feed conversion ratio (FCR; 1.600 vs 1.572 respectively; P < 0.05; Fig. 1). Adding the phytase at 250 FTU/kg already brought FCR back to the level of the PC feed, while end weight increased to 2445 g. Dosing higher levels of the phytase did not have a supplemental effect on FCR; however at 1000 FTU/kg the final end weight was 90 g higher than the end weight of the PC birds.

Figure 1- Effect on technical performance at the end of the trial (a,b: values followed by a different superscript are sign. different P < 0.05)

Addition of the phytase had a dose-response effect on bone ash percentage (Table 2). The inclusion of 1000 FTU/kg could bring back the bone ash level to that of the PC level, indicating that it can compensate almost completely for the 1.5 g/kg reduction in aP in the feed.

Table 2 – Effect of phytase addition on bone ash

Based on these digestibility data and knowing the P, Ca and CP level in the feed, it could be calculated that the phytase at 250, 500 and 1000 FTU/kg gave improvements of 1.11, 1.38 and 1.45 g/kg dig. P, 3.95, 5.67 and 5.49 g digestible protein, and of 0.11, 0.15 and 0.40 g dig. Ca per kg feed respectively.

Table 3 – Improvement in ileal digestibility (%)

IV. CONCLUSIONS

It can be concluded from this trial that this novel, intrinsic heat stable phytase has the potential to compensate for a reduction of 0.2 % protein, 0.02 % dig. Lys, 0.18 % Ca and P and 0.09 MJ/kg ME in feed while improving nutrient digestibility. The increase of 1.11, 1.38 and 1.45 g dig. P per kg of feed at the inclusion level of 250, 500 and 1000 FTU/kg is comparable with the standard matrix values of commercially available phytases.

Presented at the 32th Annual Australian Poultry Science Symposium 2021. For information on the next edition, click here.

References

Beeson LA, Walk CL, Bedford MR & Olukosi O (2017) Poultry Science 96: 2243-2253.

CVB (2018) http://www.cvbdiervoeding.nl/bestand/10501/cvb-feed-table-2018-edition2.pdf.ashx

ISO 30024 https://www.iso.org/standard/45787.html.

Shastak Y, Witzig M, Hartung K & Rodehutscord M (2012) Poultry Science 91: 2201–2209.

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Reza Abdollahi

Massey University

8 de octubre de 2023

Nice study and findings. It would be interesting to see if the inorganic P source, MCP here, could be completely removed by higher dose of phytase, especially during the finisher phase.

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Sumit Sipany

ABTL Advanced Bio-Agro Tech Ltd

17 de febrero de 2023

Mechanisms of Action for Phytase Enzymes in Poultry Diets for enhanced Phosphorus availability to Birds.?

1. Since first commercial utilisation, phytase has mainly been considered to be a tool to increase phosphourus (P) availability/digestibility from vegetable sources and so to reduce the inclusion of higher cost P sources. ??

2. Here, phytase releases the P bound in the phytate molecule, increasing the availability/digestibility of this mineral to the animal. ?

a) Thus, increasing the inclusion rate of phytase would be expected to release additional P from the indigestible feed phytate and consequently allow an even greater substitution of higher cost P sources.??

3. Phytate as an anti-nutrient:

a) As more phosphorus is removed from phytate, leading to more breakdown of intact IP-6, the less able it is to bind or chelate minerals, starch or proteins either directly or via ionic bridges (Selle & Ravindran, 2007). ??

b) Decreasing the binding of these compounds through the use of phytase may directly improve the digestibility not only of phosphorus and divalent cations such as Ca, Zn and Mg, but also indirectly increase energy and nitrogen utilization. ??

c) It is interesting that the effect of phytase on amino acid digestibility tends to be greatest on those amino acids that are prevalent in intestinal maintenance and turnover, namely cystine, threonine, proline and glycine when measured (Selle et. al., 2006).??

4. Several trials with higher doses of phytase using diets with normal levels of P have already shown better poultry performance, but this increase of performance was always correlated to an increase in P digestibility even if the diet did not have lower levels of P.

a) Phytases are digestive enzymes which release plant phosphorus from phytic acid.

b) Monogastric animals lack sufficient phytases to release the phosphorus.

c) Adding extra phytases to the diet increases phytate breakdown and consequent utilization of plant phosphorus.

d) If more phosphorus is available naturally, then less of this substance has to be added to the diet. This greatly reduces feed costs.??

5. Research findings on Phytase.

a) It has been clearly shown that phytate solubilises in the acidic region of the chicken gut, thus this is the critical area of digestion where one needs a highly efficacious phytase to work (Tamim, et al., 2004).

b) The response can vary depending if the product is thermo-tolerant and able to survive the normal pelleting process (Parr and Wyatt, 2006).

c) The intrinsically thermo-tolerant enzymes are clearly the best solution,

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