One area of innovation in the aquaculture industry lies in fish feed, specifically exploring new additives that can enhance growth, health, and the utilization of industry byproducts. Researchers are investigating sustainable feed additives to improve fish health and growth while reducing environmental impact.
A recent study examined the effects of hop acids—a byproduct of the brewing industry—as a feed additive for Nile tilapia (Oreochromis niloticus). The findings, published in the Journal of the World Aquaculture Society by scientists from the University of Florida, provide promising insights into the potential of hop acids in aquaculture.
What are hop acids?
Hop acids, derived from hops (Humulus lupulus), are known for their antimicrobial properties, particularly against Gram-positive bacteria. They are an important component of spent brewer’s yeast (SBY), a byproduct of beer production.
With the growing interest in circular economy practices, SBY and its hop acid content offer an opportunity to repurpose brewery waste into aquaculture feed. In addition to their antimicrobial action, hop acids have also been associated with antioxidant and anti-inflammatory activities in other contexts.
Study design and key findings
Researchers conducted a 56-day feeding trial to examine how the addition of hop acids to tilapia feed affected various production and quality parameters. They formulated four diets with increasing concentrations of hop acids (alpha, beta, and iso-alpha acids), ranging from 0 mg/kg (control) to approximately 1,200 mg/kg.
The low (≈60 mg/kg) and medium (≈300 mg/kg) hop acid levels in the diets were designed to mimic the concentrations that could be found if SBY from different breweries was used to replace a portion of fishmeal protein.
The study assessed:
- Growth performance: No significant differences were observed in total weight gain or feed conversion ratio (FCR) across treatments. However, fish fed a medium dose of hop acids (300 mg/kg) showed slightly higher average weights toward the end of the trial.
- Health metrics: Lysozyme activity (an immune marker) remained constant across all groups, indicating no adverse effects on fish health.
- Fillet quality: Small differences in fillet color were detected, but sensory tests revealed no significant changes in aroma, whether raw or cooked.
- Sustainability: Hop acids did not negatively affect fish growth or quality, suggesting their potential as a sustainable feed ingredient.
Implications for aquaculture
The study highlights several key takeaways:
✅ No harmful effects: Even at the highest concentration (1,200 mg/kg), hop acids did not impair fish growth, health, or fillet quality.
✅ Potential growth benefits: The medium hop acid dose (300 mg/kg) showed a slight growth advantage, suggesting possible dose-dependent benefits.
✅ Sustainable feed option: The use of SBY with hop acids could reduce waste and feed costs while maintaining fish performance.
Future research directions
While this study demonstrates the safety of hop acids in tilapia feed, further research is needed to:
- Investigate their antimicrobial effects under disease-risk conditions.
- Optimize hop acid concentrations for maximum growth benefits.
- Explore synergies with other feed additives, such as probiotics.
Conclusion
Although this study did not find significant improvements in growth or immune function when adding hop acids to tilapia feed under controlled conditions, the key takeaway is the absence of negative effects. This suggests that hop acids—whether isolated or as part of brewery byproducts like SBY—could be incorporated into tilapia diets without harming fish or compromising fillet quality.
The use of hop acids aligns with the goal of greater sustainability in aquaculture by potentially utilizing industry byproducts and offering a natural feed additive.
The study was funded by the University of Florida and the Yeoman Scholarship Foundation.
Contact
Andrew J. MacIntosh
University of Florida
520 Newell Drive rm126, Gainesville, FL 32611, USA.
Email: andrewmacintosh@ufl.edu
Razieh Farzad
University of Florida
120 Newell Drive rm104, Gainesville, FL 32611, USA.
Email: rfarzad@ufl.edu
Reference (open access)
Lee, J. K., Farzad, R., Lee, T., Ying Chuah, S. X., Omidvar, R., Sims, C., Zhang, B., Ropicki, A., & MacIntosh, A. J. (2025). Effect of hop acid inclusion as a feed additive on Nile tilapia, Oreochromis niloticus, production, lysozyme activity, fillet color, and aroma. Journal of the World Aquaculture Society, 56(2), e70014. https://doi.org/10.1111/jwas.70014
Editor at the digital magazine AquaHoy. He holds a degree in Aquaculture Biology from the National University of Santa (UNS) and a Master’s degree in Science and Innovation Management from the Polytechnic University of Valencia, with postgraduate diplomas in Business Innovation and Innovation Management. He possesses extensive experience in the aquaculture and fisheries sector, having led the Fisheries Innovation Unit of the National Program for Innovation in Fisheries and Aquaculture (PNIPA). He has served as a senior consultant in technology watch, an innovation project formulator and advisor, and a lecturer at UNS. He is a member of the Peruvian College of Biologists and was recognized by the World Aquaculture Society (WAS) in 2016 for his contribution to aquaculture.
