ISSUE FOCUS FEED & ADDITIVE MAGAZINE August 2025 79 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. Time to SDA Peak Total SDA Duration SDA Scope SDA Coefficient (CSDA) 8.8–10.7 hours 22.1–22.6 hours 2.0–2.9 14.8–16.4% Time after feeding to reach maximum metabolic rate Total time of elevated metabolism post-feeding Ratio of peak postprandial to baseline metabolism % of meal energy expended as SDA Parameter Description Typical Range Table 1. SDA Parameters in Aquaculture Source: Le Boucher et al. (2025)
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