Measurement of feeding motivation in sheep and the effects of food restriction

• Published in: Applied animal behaviour science Vol. 132; no. 3; pp. 121 - 130
• Main Authors: Verbeek, Else, Waas, Joseph R., McLeay, Lance, Matthews, Lindsay R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2011; [Amsterdam]: Elsevier Science
• Subjects: animal growth; Behavioural demand; demand elasticities; demand functions; ewes; feeding level; Feeding motivation; food availability; Food restriction; foods; Hunger; motivation; Ovis aries; Sheep; walking; Welfare; Behavioural demand; Sheep; Hunger; Welfare; Feeding motivation; Food restriction
• ISSN: 0168-1591; 1872-9045
• DOI: 10.1016/j.applanim.2011.03.014

The availability of food is a crucial factor determining the health and growth of animals. Prolonged or severe food restriction will trigger the subjective state of hunger, which could potentially reduce welfare. We refined a methodology for the measurement of feeding motivation as an indicator of hunger, evaluated the effects of food restriction on feeding motivation in ewes ( Ovis aries) and applied a behavioural demand analysis to the data. Sixteen ewes were exposed to five different cost levels (i.e., 2, 6.6, 12.1, 22, or 40 m walking distances per reward) and two feeding levels (24 h restriction and an un-restricted control). We found that 24 h restricted ewes worked for a higher number of rewards ( P < 0.001), walked a greater total distance ( P < 0.001) and approached the feeding station faster on the first visit ( P < 0.001). Therefore, the methodology was able to detect differences in feeding motivation between restricted and control ewes and is a potential indirect indicator of hunger. A generic demand function fitted to the data showed that the elasticity of demand, the maximum price paid ( P max) and maximum expenditure ( O max) were not sensitive indicators of motivation, probably because we did not generate a complete demand curve. Imposing a cost by providing sheep with the opportunity to walk for their food could be a valuable tool in establishing acceptable feeding levels from an animals’ perspective. However, more research on validating behavioural demand measures as indicators of motivation is needed.