Just Accepted

This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.

Additivity and Associate Effects of Metabolisable Energy and Ileal Amino Acid Digestibility in Broiler Diets Combining Sorghum with Different Protein Sources

Asad Sultan, Xiuhua Li , Dagong Zhang, Wayne Bryden

Abstract

Context: Poultry diets consist of a number of ingredients contributing specific amounts of nutrients and assumes that the supply from each ingredient is additive when diets are formulated. However, the additivity of apparent metabolisable energy (AME) and ileal amino acid digestibility in broiler diets combining sorghum with different protein sources has not been examined. Aim: To determine the additivity of AME along with ileal digestibility values for protein and amino acids in diets combining sorghum with different protein sources. Methods: The digestibility assays, based on semi-purified diets containing sorghum, sunflower meal (SFM), meat and bone meal (MBM), soybean meal (SBM), canola meal (CM), and cottonseed meal (CSM), were fed individually, or sorghum was combined with the different protein sources. Each diet was fed to three cages of twelve, 17 day-old broilers for 7 days. Excreta was collected for the final 3 days and at the end of the assay, digesta was collected from the terminal ileum for digestibility determination. Key results: When sorghum was mixed with the different protein sources all predicted values for protein digestibility were additive but for AME only the value for sorghum + SFM was additive. All other predicted AME values for sorghum combinations were different (P<0.05) from the determined value. There were significant (P<0.05) differences between predicted and determined amino acid digestibility coefficients, but amino acids showing associate effects varied between the different sorghum protein source combinations. Conclusion: Overall, the present results indicate that caution should be exercised when predicting the AME and apparent ileal amino acid digestibility values for sorghum-based diets from values determined with individual feed ingredients. Implications: The study indicates that positive and negative interactions are likely to occur between dietary ingredients in mixed diets that have implications for both energy and protein utilisation.

AN24159  Accepted 09 July 2024

© CSIRO 2024