Effects of pretreatment in all-plant feedstuff with microbial phytase on phosphorous utilization and growth performance of Nile tilapia Cao, Ling and James Diana University of Michigan Wang Weimin Huazhong Agricultural University Wuhan China Yang Yi Shanghai Ocean University Shanghai China

Development (USAID) Grant No. EPP-A-00-06-00012-00. Travel funding for this presentation was provided by AquaFish Collaborative Research Support Program AquaFish CRSP USAID The Aquaculture CRSP is funded in part by United States Agency for International Development (USAID) Grant No. EPP-A-00-06-00012-00. The opinions expressed herein are those of the authors and do not necessarily reflect the views of the US Agency for International Development.

Outline Background Experimental design Results Conclusions Acknowledgement

1. Background Decrease of annual fishmeal production Fishmeal substitution by plant proteins High concentration of phytate in plant proteins

Phytate and phytase enzyme Phytate = phytin = phytic acid Up to 80% of the total P content in plants may be present in the form of phytate and is practically not available for monogastric or agastric aquatic animals.

Table 1. Phytate contents in plants or plant products (NRC, 1993)

Phytase: An enzyme specific to hydrolyze phytate, naturally found in animals, plants and microorganisms

Figure 1. Action of phytase (Baruah et al. 2004)

Table 3. Commercial information of microbial phytase (Cao et al. 2007)

Table 4. Optimum dose of phytase addition in diets of different fish species (Cao et al. 2007)

2. Experimental design 2.1 Pretreatment trial Objectives: ＊ Find out the most efficient phytase dose for treating plant ingredients

Enzyme solution (10 U/ml) pH 5.5 Citric acid buffer Phytase (5000 U/g) Enzyme solution (10 U/ml) Mix with plant ingredients (W:V=1:1) Oven 55 ℃ 5～6 h Sampling Chlorine anion 100-200 mesh AG1-X4 （Bio-Rad Laboratory, USA）

2.2 Growth trial Objectives: ＊Find out the optimum addition dosage for growth performance of tilapia juveniles. ＊Determine the best replacing amount for inorganic phosphorous by phytase.

3. Results 3.1 Pretreatment Soybean meal Mix plant ingredients

3.2 Growth performance

4. Conclusion The optimal dose of phytase for the pretreatment of plant ingredients is 1,000 U kg -1, which can efficiently convert phytate P to available P and replace 50% of the inorganic P supplementation to the diets for Nile tilapia juveniles without affecting their growth performance, apparent digestibility coefficients of both crude protein and phosphorous. The addition of phytase in the diets can reduce the use of inorganic P, enhance the utilization of P in plant ingredients, and thus minimize the P discharge to the environment.

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