Research Summary - Exploring Physiological Indicators of Farmed Insect Welfare (Rethink Priorities)

Over 2.5 trillion insects are reared annually for food and feed, and this upward trend is projected to continue. However, little research is available on farmed insect welfare compared to vertebrates. This paper aims to guide efforts to fill this knowledge gap by evaluating physiological indicators of farmed insect welfare, assessing their correctness, usefulness, and feasibility to prioritize future research. These operational indicators are categorized as 'short-term' (correct and feasible on farms), 'long-term' (correct but not feasible on farms), or 'low' priority.

This review identified seven potential operational indicators as short-term priorities for further research: heart rate, heart rate variability, fat mass, visual body condition scoring, body mass and scaling data, physical injury, and volatile organic compounds. Five indicators are classified as long-term priorities: biogenic amines, neurohormones, markers of oxidative stress, brain region volumes, and cuticular hydrocarbon profiles. Changes in total cuticular melanization, fever/body temperature, molecular markers of immune function, respiratory patterns, heart rate pumping, and growth rate were categorized as low priority. Further research is warranted into other operational welfare indicators, such as behavioral indicators or telomere attrition, and into valid indicators of affective states. Biogenic amines, markers of oxidative stress, and shifts in brain region volumes are suggested as the most likely valid markers of affective states in insects.