An investigation into the causation of chewing behaviour in growing pigs: The role of exploration and feeding motivation

Growing pigs spend a considerable amount of time chewing substrates in their environment. However, it is currently unclear whether chewing behaviour reflects feeding motivation, exploratory motivation or a combination of both, Therefore, the aim of this paper was to test the hypothesis that the initial exploratory chewing of a novel substrate may acquire nutritional feedback which could reinforce feeding motivated chewing leading to the modification of foraging behaviour. This hypothesis was tested by allowing pigs, with either a high or low level of feeding motivation, to chew an initially novel length of tubing which exuded either a sucrose solution, a saccharin solution, or water. A measure of exploratory activity was obtained by also providing each pig with an identical control-tube which exuded only water, The sucrose solution provided a sweet taste and a source of energy, the saccharin provided only a sweet taste, and the water provided neither. The results indicated that the chewing behaviour directed towards the control-tube was representative of exploratory activity because it decreased to a consistent basal level and was not affected by feeding motivation. It was also found that chewing behaviour was slightly reinforced by a sweet taste, but strongly reinforced and perpetuated by a sweet taste which is paired with a supply of nutrients. Therefore, it was concluded that growing pigs can gather nutritional information during exploratory chewing, and furthermore, this nutritional feedback may modify foraging behaviour to correct specific nutrient deficiencies present in an individual's internal state.