Protein Digestibility in Poultry
Over the past 60 years, the poultry industry has advanced significantly, with broiler production becoming the most efficient animal industry, largely due to genetic selection. Feed accounts for 70–80% of broiler production costs, with protein being the second most expensive dietary component. Proteins, made of α-amino acids (AAs), are essential for tissue development and function, primarily supplying AAs for protein synthesis. Optimal bird growth requires accurate AA balance and digestibility knowledge.
Understanding AA digestibility is crucial for efficient feed formulation. It is commonly measured using ileal digesta or excreta analysis. However, excreta-based measurements are affected by microbial activity in the ceca. Ileal digestibility avoids these issues, and standardised ileal digestibility (SID) is now preferred over apparent ileal digestibility (AID), as SID accounts for endogenous AA losses.Not all ingested protein is absorbed; undigested protein undergoes microbial fermentation in the hindgut. Protein digestion starts in the proventriculus with HCl (hydrochloric acid) and pepsin and continues in the small intestine via pancreatic enzymes like trypsin, chymotrypsin, elastase, and carboxypeptidases, each targeting specific peptide bonds.Limitations to Protein DigestionProtein sources differ in composition and digestibility. Antinutritional factors (ANFs) such as protease inhibitors, phytate, and non-starch polysaccharides (NSPs) impair digestion and increase endogenous AA losses. Raw soybeans, for example, contain heat-sensitive ANFs. Improper processing can either leave these inhibitors active or degrade AAs (e.g., Maillard reaction), especially Lys, Cys, Arg, Thr, and Ser.Protein digestion efficiency is also influenced by bird age, with young chicks having immature digestive systems. Other factors include bird class, gender, and health.Improving Protein UtilisationTypically, only 70–75% of dietary energy and 75–80% of protein in broiler diets is utilised, with the rest lost in excreta. Enhancing digestibility involves improving protein accessibility and degradation into absorbable peptides and AAs. Strategies include:
Instructor Bio
Dr Reza Abdollahi currently works as an Adjunct Associate Professor of Poultry Nutrition for the Monogastric Research Centre, at Massey University. He is also founder and president of “A2Z Poultry Feed DynamikZ”, an international independent research and consultancy firm based in France. Dr Abdollahi received his PhD from Massey University, New Zealand on the influence of feed processing on the performance, nutrient utilization, and gut development of poultry. He has published in top-ranking Animal Science Journals and already has over 200 scientific communications, including 91 peer-reviewed articles and two book chapters, to his credit. As an invited and keynote speaker, Dr Abdollahi has presented his work at several international conferences such as European Poultry Conference (EPC, 2014), European Symposium on Poultry Nutrition (ESPN, 2017), International Broiler Nutritionists’ Conference (2014, 2017, 2024), Asia-Pacific Poultry Conference (2018), Australian Poultry Science Symposium (APSS, 2019), First International Feed Technology Conference (IFTC, 2019), 2021 PSA Annual Meeting, and many international industry workshops and conferences. His research interest has a strong applied focus and is relevant to the poultry industry current challenges. His current interest is poultry nutrition focusing on feed processing, feed evaluation, and nutrient utilization