Specific Dynamic Action in aquaculture is reshaping the industry by revealing how metabolic responses to feeding can influence growth, efficiency, and sustainability. By examining the energy costs of digestion and factors that affect them—like feed composition, temperature, and species— Specific Dynamic Action offers a promising path to optimise production. But how can these insights be practically applied across diverse systems and species?
By Samreen Aushiq & Mehreen Altaf & Ishfaq Nazir Mir & Pankaj Gargotra, Fish Nutrition and Biochemistry, Faculty of Fisheries, SKUAST-Kashmir
In the constantly changing world of aquaculture, the pursuit of sustainable practices and innovative solutions remain essential. One such dynamic action gaining traction is Specific Dynamic Action (SDA), a forward-thinking approach revolutionizing the way we cultivate aquatic life. With its potential to enhance productivity, minimize environmental impact, and meet the growing global demand for seafood, specific dynamic action represents a promising frontier in the realm of aquaculture.
Historically termed “specific dynamic effect” (Beamish, 1974), SDA has been described using various synonyms, including food heat increment, calorigenic effect, and dietary thermogenesis (McCue, 2006). Secor (2009) offers a comprehensive review of these terms. Accurate assessment of SDA is essential for improving feed efficiency and energy budgeting in aquaculture systems.
SDA refers to the increase in metabolic rate following food ingestion, representing the energetic costs of digestion, absorption, and assimilation of nutrients in fish and other aquatic animals (Goodrich et al., 2024). Also known as the thermic effect of food (TEF) or dietary-induced thermogenesis (DIT), SDA is one component of total metabolism, along with resting metabolic rate and physical activity. It contributes significantly to the overall metabolic demands of aquatic organisms and is a key factor in aquaculture for optimizing feed utilization and growth performance (Elvy et al., 2022).
The role of SDA in aquaculture is diverse and serves multiple purposes. Primarily, it aims to optimize the growth and development of aquatic organisms by understanding and harnessing their metabolic responses to various environmental factors, such as temperature, oxygen levels, and feed composition. By tailoring management practices based on these metabolic dynamics, specific dynamic action seeks to improve feed efficiency, enhance growth rates, and ultimately maximize production yields. Additionally, it plays a crucial role in promoting environmental sustainability by reducing nutrient waste and minimizing the ecological footprint of aquaculture operations. Overall, the purpose of specific dynamic action is to revolutionize aquaculture practices by exploiting biological processes to achieve higher efficiency, productivity, and sustainability in seafood production.
SDA is measured as the rise in oxygen consumption after feeding and is most accurately assessed in species that remain still during digestion. However, spontaneous activity during the postprandial period can lead to overestimations of both peak and total SDA due to increased oxygen demand above standard metabolic rate (SMR). In mammals, measuring SDA is more complex and requires prolonged monitoring under controlled conditions to return to basal metabolic rate, often taking over 10 hours (James, 2005).
Nutrient composition strongly influences SDA: Protein produces the highest thermic effect (~30% of its energy), followed by glucose (5–10%), fat (2–5%), and alcohol (0–8%). Other dietary components like caffeine and spices can also increase metabolic rate. For example, spices can raise it by up to 25% compared to non-spiced meals.
FACTORS INFLUENCING SPECIFIC DYNAMIC ACTION
Several factors influence SDA in aquaculture:
1. Feed Composition: High protein or lipid feeds increase SDA due to higher digestion energy demands.
2. Feed Size: Larger feed particles may require more energy to break down.
3. Water Temperature: Higher temperatures elevate metabolic rates, including SDA.
4. Species and Life Stage: Different species and younger individuals often exhibit higher SDA.
5. Feeding Frequency: Frequent feeding sustains metabolic activity, though some studies suggest meal frequency has minimal impact if total intake remains constant.
6. Environmental Conditions: Water quality, oxygen levels, and stocking density affect metabolism and SDA.
7. Physiological State: Health, stress, and reproductive status influence SDA response.
8. Genetic Factors: Genetic variation affects individual metabolic responses.
9. Water Quality: Optimal water conditions support efficient SDA and growth.
Understanding these factors is essential for improving feed efficiency and growth in aquaculture systems.
Even after digestion and absorption, nutrients particularly proteins are not fully accessible to fish without additional metabolic processing. To use amino acids for energy, fish must first undergo deamination, an energy-consuming process that removes the amino group. This contributes to SDA, which is externally observed as an increase in oxygen consumption shortly after feeding, followed by elevated ammonia excretion (Brett & Groves, 1979).
The proportion of amino acids deaminated varies depending on environmental and nutritional conditions. Fish maintained at low temperatures or on restricted rations often deaminate most or all amino acids, using them primarily for energy. In contrast, fish experiencing rapid growth and consuming high-protein diets deaminate a smaller proportion of amino acids, although the absolute amount may still be significant enough to result in a high SDA. The energy required for deamination can be supplied by carbohydrates or fats, which can reduce the need to metabolize protein for energy. This “protein-sparing” effect, particularly from carbohydrates, has been widely applied in salmonid aquaculture to lower feed costs while maintaining growth. However, the role of lipids in protein sparing has received less attention. Although SDA can be reduced through dietary strategies, it cannot be entirely eliminated due to the inherent costs of nutrient processing.
MEASUREMENT AND CALCULATION
To measure and calculate SDA in aquaculture, following are the steps:
1. Experimental Setup: Design an experiment where you can monitor the metabolic rate of the fish before and after feeding.
2. Baseline Measurement: Measure the baseline metabolic rate of the organisms. This can be done using respirometry techniques, where you measure oxygen consumption or carbon dioxide production over a period of time.
3. Feeding: Feed the organisms with a known quantity and type of food. It’s essential to ensure that the food is similar to their natural diet to minimize confounding variables.
4. Post-Feeding Measurement: Again after feeding measure the metabolic rate of the organisms. To capture the peak metabolic response to feeding this should be done for a sufficient period of time.
5. Data Analysis: Calculate the difference between the post-feeding metabolic rate and the baseline metabolic rate. This difference represents the increase in metabolic rate due to the specific dynamic action of feeding.
6. Statistical Analysis: Perform statistical analysis to determine if the observed increase in metabolic rate is significant and to compare SDA among different treatments or species.
7. Repeat and Validate: Repeat the experiment multiple times to ensure reproducibility and validate the results.
It’s important to note that the specific protocols and techniques for measuring SDA may vary depending on the species of and the specific research objectives.
Additionally, consider factors such as temperature, salinity, and other environmental conditions that may influence metabolic rate and SDA.
OPTIMIZING SDA FOR IMPROVED EFFICIENCY
SDA plays a critical role in influencing feed conversion ratios (FCR) within aquaculture. It affects feed requirements, nutrient utilization efficiency, and the metabolic responses of species to feeding. Species exhibiting higher SDA tend to require an increased amount of feed to satisfy their energy needs, which leads to greater feed consumption for equivalent output and consequently raises the FCR. Therefore, the implementation of effective management techniques and feed optimization strategies is essential to mitigate the impact of SDA on FCR while fostering sustainable aquaculture practices.
Feed Formulation: To improve efficiency, choose feeds that induce lower SDA responses. High-quality, easily digestible feeds with balanced nutrient profiles can reduce the energy expended during digestion, leading to better feed conversion ratios and overall growth performance.
Feeding Strategies: To optimize SDA, implement feeding regimes that align with the metabolic rhythms of the cultured species. For example, feeding during times of peak metabolic activity can maximize nutrient uptake and minimize energy wastage associated with SDA.
FUTURE DIRECTIONS AND RESEARCH
Advancements in SDA Monitoring
The advances in SDA monitoring are enhancing our understanding of metabolic processes in aquaculture and contributing to the development of more sustainable and efficient feeding practices. By integrating cutting-edge technologies and interdisciplinary approaches, researchers and aquaculturists are working towards maximizing metabolic efficiency and minimizing environmental impacts in aquaculture operations. some of the recent advancements include;
• Real time monitoring technologies
• Biochemical markers
• Nutrigenomics
• Remote sensing techniques
• Integrated multi-trophic aquaculture (IMTA) system
CONCLUSION
In conclusion, the study of specific dynamic action in aquaculture offers valuable insights into the metabolic responses of cultured species to feeding, with significant implications for feed efficiency, growth performance, and environmental sustainability. By understanding the energy expended during digestion and processing of food, aquaculturists can optimize feeding strategies, improve feed conversion ratios, and minimize environmental impacts. By integrating recent advancements in SDA monitoring into aquaculture practices, we can strive towards more sustainable and efficient production methods, ensuring the long-term viability of aquaculture as a vital source of nutritious food for a growing global population.
References
1.Beamish, F. W. H. (1974). Apparent specific dynamic action of largemouth bass, Micropterus salmoides. Journal of the Fisheries Research Board of Canada, 31(11), 1763–1769. https://doi.org/10.1139/f74-215
2.Brett, J. R., & Groves, T. D. D. (1979). Physiological energetics. In W. S. Hoar, D. J. Randall, & J. R. Brett (Eds.), Fish physiology: Bioenergetics and growth (Vol. 8, pp. 279–352). Academic Press.
3.Elvy, J. E., Symonds, J. E., Hilton, Z., Walker, S. P., Tremblay, L. A., & Herbert, N. A. (2022). The relationships between specific dynamic action, nutrient retention and feed conversion ratio in farmed freshwater Chinook salmon (Oncorhynchus tshawytscha). Journal of Fish Biology. https://doi.org/10.1111/jfb.15293
4.Goodrich, H. R., Wood, C. M., Wilson, R. W., Clark, T. D., Last, K. B., & Wang, T. (2024). Specific dynamic action: the energy cost of digestion or growth? Journal of Experimental Biology, 227(7), jeb246722. https://doi.org/10.1242/jeb.246722
5.Le Boucher, R., Chung, W., Lin, J. N. K., En, L. T. S., & Sin, L. C. (2025). Evaluating metabolic rate and specific dynamic action in recirculating aquaculture systems: Influence of stocking density and feeding level in Barramundi (Lates calcarifer). SSRN. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=5148435
6.McCue, M. D. (2006). Specific dynamic action: A century of investigation. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 144(4), 381–394. https://doi.org/10.1016/j.cbpa.2006.03.011
7.Secor, S. M. (2009). Specific dynamic action: A review of the postprandial metabolic response. Journal of Comparative Physiology B, 179(1), 1–56. https://doi.org/10.1007/s00360-008-0283-7
8.P.T. James,ENERGY | Requirements,Editor(s): Benjamin Caballero, Encyclopedia of Human Nutrition(Second Edition),Elsevier,2005,Pages 125-131,ISBN 9780122266942, https://doi.org/10.1016/B0-12-226694-3/00101-0
