Diet selection and animal state: an integrative framework

Abstract

In the present paper we deal with the problems of explaining and predicting diet selection of animals under controlled conditions, i.e. conditions that can be described and in which any influences of the environment can be either controlled or at least monitored. Diet selection is considered within an integrative framework of feeding behaviour that views both food intake and diet selection as an outcome of the animal's internal state and knowledge of the feeding environment. Three questions that arise from the framework are considered: (1) how do animals learn about foods available to them as a choice? (2) what changes in internal state affect diet selection? (3) how much time is needed for a change in the animal's internal state to be detected and for it to react to this change through a modification of its diet selection? It is proposed that animals have developed behavioural mechanisms that allow them to recognize foods on the basis of their nutritional as well as other properties. The rate at which animals learn about foods depends largely on the extent of the animal's deficiency and on the extent of the post-ingestive consequences induced by the foods. There is little evidence that animals modify their diet selection in response to short-term systemic fluctuation of their internal environment. On the other hand, long-term changes in the internal state of the animal lead to consequent long-term changes in diet selection. The time needed for a change in diet selection to be observed depends on the deviation created in the animal's internal state, either as a result of a physiological change or as a consequence of feeding. Thus, a more appropriate question to consider is not 'what time period matters to the animal?' but 'how much change or deviation in the internal state is the animal prepared to accept?'

Behavioural adaptations of sheep to repeated acidosis challenges and effect of yeast supplementation

“…Indeed, during this first challenge, the sheep ate all the concentrate offered for the first 2 days of this challenge and then refused half of it during the next 3 days. Kyriazakis et al (1999) suggested that animals adjust their dietary selection in response to a significant physiological change, which in our case could be an altered rumen state. Nevertheless, the decrease in wheat consumption over the following days did not allow a significant increase in ruminal pH at the end of challenge 1.…”

Human eating behaviour in an evolutionary ecological context

“…Animal feeding behaviour has been described by Kyriazakis et al (1999) as a continuous close-looped system, whereby food intake and diet selection influence, and in turn are influenced by, an animal's internal state and knowledge of its feeding environment. The internal state changes as a direct consequence of feeding (or lack of it) or other stimuli.…”

On the application of mixed hidden Markov models to multiple behavioural time series

“…hormone and metabolite levels or protein and lipid stores), but also externally based motivational aspects (e.g. perceived predation risk) [8][9][10]. Estimates of the motivational state could be derived from physiological measures like hormone profiles [8], or from behaviours that are specific for a certain context, e.g.…”