Integrating nutrition: a geometrical approach

Abstract

Abstract We present and illustrate using data from insects an integrative approach to modelling animal nutrition. This framework enables the unification within simple geometrical models of several nutritionally relevant measures. These include: the optimal balance and amounts of nutrients required to be ingested and allocated to growth by an animal over a given time period (the intake and growth targets, respectively); the animal's current state in relation to these requirements; available foods and the consequences for the animal's state of ingesting them; the amounts of ingested nutrients that are retained and eliminated; and animal performance. Data are presented on intake targets in insects, illustrating how they change over various time‐scales (physiological, developmental, and evolutionary). Most importantly, the geometrical approach enables a clear description to be made of the trade‐offs reached by animals in regulating their nutritional balance. Animals given a nutritionally balanced food, or two or more imbalanced but complementary foods, can satisfy their nutrient requirements. However, those eating non‐complementary imbalanced foods must reach a suitable compromise between over‐ingesting some nutrients and under‐ingesting others. Data are presented comparing the rules of compromise for protein and carbohydrate ingestion in grass‐feeding ( Locusta migratoria ) and polyphagous ( Schistocerca gregaria ) locusts.