Relationship between feeding, stereotypies, and plasma glucose concentrations in food-restricted and restrained sows

Previous work has shown that stereotypies, such as chain manipulation and excessive drinking, only develop in food-restricted sows. Furthermore, once stereotypies have been developed, ingestion of a small meal specifically stimulates the performance of stereotypies. These results suggest that the occurrence of stereotypies may strongly depend on the individual's nutritional status. As glucose is one of the main metabolic fuels, the present experiment investigated whether individual differences and/or daily variations in levels of chain manipulation and excessive drinking are correlated to individual differences and/or daily variations in pre- or postfeeding glucose concentrations. Blood samples were taken at regular intervals prior to, during, and after feeding, from sows that had developed stereotypies to different degrees over a period of 110 days of restrictive housing and feeding conditions. Glucose concentrations were low prior to and high after feeding. Levels of stereotypies showed similar variations, suggesting that the performance of stereotypies is not related to low glucose concentrations. Furthermore, whilst sows differed consistently in glucose concentrations, no correlations were found between individual glucose concentrations and stereotypies. Similarly, no correlations were found between glucose concentrations and chain manipulation or drinking on a sample to sample basis. These data show that although performance of stereotypies is strongly dependent on feeding regime, it is not related to plasma glucose concentrations.