Barley protein - improving nutrient digestibility for salmon

Barley protein - improving nutrient digestibility for salmon

Nutrient digestibility

A controlled digestibility study was conducted on juvenile salmon with a fishmeal-rich control diet and test diets replacing 30% of fishmeal with plant proteins, including: barley protein concentrate (BPC), soy protein concentrate (SPC), corn gluten meal (CGM), Hipro sunflower meal (SFM), and guar meal Korma (GMK).

Protein digestibility is a fundamental metric for evaluating feed ingredients. BPC achieved an apparent protein digestibility coefficient (ADC) of 84.2%, comparable to CGM (83.5%) and GMK (82.6%), and higher than SFM (80.7%). Although slightly lower than SPC (86.7%), BPC's protein digestibility remains well within a competitive range for salmon diets.

The lipid digestibility coefficient of BPC reached a high of 90.9%, showing that salmon can efficiently utilize energy from fats. This level of fat utilization not only meets high energy demands for growth but also surpasses SPC (87.7%), CGM (89.0%), GMK (89.9%), and SFM (86.6%). In terms of energy, BPC's energy ADC reached 86.0%, demonstrating a stable contribution to total dietary energy. This indicates that BPC is an effective ingredient choice when optimizing nutritional balance in salmon feeds.

Phosphorus digestibility, an important environmental sustainability indicator, of BPC reached a peak of 33.6%, surpassing SPC (30.6%), CGM (29.7%), SFM (24.8%), and GMK (18.6%). This advantage contributes to reducing phosphorus discharge into the environment, meeting ecological protection requirements.

Lysine and amino acid digestibility

Amino acid digestibility trends parallel crude protein digestibility. BPC achieved an ADC of 82.3% for lysine (SPC 88.7%; CGM 80.9%; SFM 77.8%). Digestibility coefficients for both methionine and leucine exceeded 86%, while arginine reached 89.7%. These values confirm that BPC provides a highly digestible source of essential amino acids, supporting balanced feed formulation.

The dietary treatments had only minor effects on foregut histology. However, fish fed diets containing BPC tended to have taller villi, a higher density of goblet cells, and a higher proportion of acidic mucin compared to those fed lower-quality proteins such as GMK or SFM. This indicates that BPC contributes to maintaining a healthy gut structure in salmon.

In other farmed species, BPC shows protein digestibility of 88-92%, fat digestibility of >93% and phosphorus digestibility of 33-50%, confirming its consistent performance in both freshwater and saltwater fish. BPC offers competitive protein digestibility and superior phosphorus utilization, delivering both nutritional and environmental benefits.