by Shay Sadr
Soybean meal has long been the major protein source in broiler diets because of its favourable amino acid profile and consistent nutritional value. However, increasing interest in feed sustainability, supply security and the use of locally available ingredients has encouraged poultry nutritionists to look more closely at alternative protein sources.
Field peas and faba beans are among the grain legumes with potential to partially replace soybean meal in broiler diets. In Australia, greater use of locally grown legumes could provide an opportunity to diversify feed ingredients and reduce reliance on internationally traded protein sources. However, replacing soybean meal is more complex than simply matching crude protein or amino acid specifications. Changes in ingredient composition can also influence feed intake, nutrient absorption and the physiological responses of the gastrointestinal tract.
Our recent research at the University of Sydney has been exploring this interaction between legume inclusion, broiler performance and intestinal function.
In our feeding study recently published in Poultry Science, field peas and faba beans were used to partially or completely replace soybean meal within reduced protein diets. Interestingly, energy utilisation and protein and starch digestibility remained relatively comparable between the soybean meal control and the legume-based diets. However, birds consuming the legume diets generally had lower feed intake and body weight and poorer feed conversion.
This raised an important question: if conventional measures of nutrient digestibility were not substantially compromised, what else might be contributing to the performance response?
To investigate this, our recently study published in BMC Genomic examined gene expression in the jejunum, the major region of the small intestine involved in nutrient digestion and absorption. We focused on genes associated with nutrient transport, intestinal barrier integrity, mucosal function and appetite-related signalling.
The results showed that the response to the legume-based diets extended well beyond nutrient digestibility. Glucose transporter expression was largely unaffected, but expression of the peptide transporter PepT1 and amino acid transporter y+LAT1 was altered by dietary treatment. Several genes involved in intestinal barrier function, including claudin-3, claudin-2 and ZO-1, were also reduced in birds fed legume-containing diets. Changes were also observed in genes associated with mucosal function including MUC2 and GLP-2. Expression of NPY and POMC, two genes associated with regulation of appetite and energy balance, was reduced across the legume-containing treatments. Several of the genes related to intestinal barrier function and appetite signalling were also correlated with body weight gain and feed efficiency.
These findings complement our recent review, focusing on nutrient transporters in broiler chickens, which highlights how nutrient transporter expression is influenced by diet, age, environmental stress and health status. Nevertheless, changes in transporter expression do not necessarily indicate better or poorer nutrient utilisation but may indicate the bird adapting to changes in nutrient availability or intestinal conditions.
These findings do not yet allow us to conclude that a particular gene caused the reduction in feed intake or growth rate. However, they highlight that the performance response to alternative ingredients may involve a much more complex interaction between diet structure, intestinal integrity, nutrient sensing and gut–brain signalling than is captured by digestibility measurements alone.
Further reading:
Sadr, V.S., Toghyani, M., Liu, S.Y. & Barekatain, R. (2026). Targeted jejunal gene expression analysis suggests that high legume inclusion in reduced-protein diets is associated with increased intestinal permeability and altered gut barrier and appetite-regulating genes in broiler chickens. BMC Genomics. https://link.springer.com/article/10.1186/s12864-026-13238-0
Sadr, V.S., Macelline, S.P., Kim, E., Toghyani, M., Hamungalu, O., Wester, T.J., Barekatain, R. & Liu, S.Y. (2026). Potential of field peas and faba beans as protein-rich alternatives for partial or full replacement of soybean meal in broiler chicken diets. Poultry Science, 105(1), 106191.
Sadr, V.S., Quinteros, J.A., Liu, S.Y. & Barekatain, R. (2025). Nutrient transporters in broiler chickens: intestinal gene expression profiles, functional roles, and influencing factors. Journal of Animal Science and Biotechnology, 16, 165.
