Prediction of ingredient quality and the effect of a combination of xylanase, amylase, protease and phytase in the diets of broiler chicks. 2. Energy and nutrient utilisation

Abstract

1. In order to investigate the effects of xylanase, amylase, protease and phytase in the diets of broiler chickens containing graded concentrations of metabolisable energy (ME), two 42-d experiments were conducted using a total of 2208 broiler chicks (8 treatments with 12 replicate pens in each experiment).

2. Four diets including one positive and three negative control diets were used. Three maize/soybean meal-based negative control (NC) diets were formulated to be identical in available phosphorus (P), calcium (Ca) and amino acids but NC1 contained approximately 0·17 MJ/kg less ME than NC2 and approximately 0·34 MJ/kg less ME than NC3. A positive control (PC) was fed for comparison and was formulated to be adequate in all nutrients, providing approximately 0·63 MJ/kg ME, 0·13% available P, 0·12% Ca and 1 to 2% amino acids more than NC1.

3. The reduction in nutrient density between NC1 and PC was determined using ingredient quality models Avicheck™ Corn and Phycheck™ that can predict the response to exogenous enzymes in maize/soybean meal-based broiler diets. Supplementation of each diet with or without a cocktail of xylanase, amylase, protease and phytase gave a total of 8 dietary treatments in a 4 × 2 factorial arrangement. The same treatments and diet designs were used in both experiments but conducted in different locations using different batches of maize, soybean meal and minor ingredients.

4. In both experiments, digestibility was improved by the addition of exogenous enzymes, particularly those for P, Ca and certain amino acids. In addition, the supplementation of the PC with enzymes elicited a positive response indicating that over-the-top addition of xylanase, amylase, protease and phytase may offer a nutritionally and economically viable alternative to feed cost reduction.

5. It can be concluded that the digestibility of nutrients by broilers fed on maize/soybean meal-based diets can be improved by the use of a combination of xylanase, amylase, protease and phytase.

Acknowledgements

Danisco Animal Nutrition financially supported this work. The authors are grateful to technical staff at Danisco Innovation and Sciantec Analytical Services for analysis of diets and ingredients. The assistance of Fred Haan of Purdue University Poultry Research Center, Yinka Olukosi, Josh Jendza, Ernest Nyannor and Pat Jaynes are gratefully acknowledged. In addition the authors would like to acknowledge the assistance of Peter Trappett, Tanya Nagle, Max Kemsley, Robert Morton, Paul Kent and Kerry Barram of Poultry Research and Development Centre, Brisbane. Journal paper number 2005-17712 of the Purdue University Agricultural Research Program.