Feeding behaviour in ruminants: a consequence of interactions between a reward system and the regulation of metabolic homeostasis

Abstract

Feeding behaviour, through both diet selection and food intake, is the predominant way that an animal attempts to fulfil its metabolic requirements and achieve homeostasis. In domestic herbivores across the wide range of production practices, voluntary feed intake is arguably the most important factor in animal production, and a better understanding of systems involved in intake regulation can have important practical implications in terms of performance, health and welfare. In this review, we provide a conceptual framework that highlights the critical involvement and interconnections of two major regulatory systems of feeding behaviour: the reward and the homeostatic systems. A review of the literature on ruminants and rodents provides evidence that feeding behaviour is not only shaped by homeostatic needs but also by hedonic and motivational incentives associated with foods through experiences and expectations of rewards. The different brain structures and neuronal/hormonal pathways involved in these two regulatory systems is evidence of their different influences on feeding behaviours that help explain deviation from behaviour based solely on satisfying nutritional needs, and offers opportunities to influence feeding motivation to meet applied goals in livestock production. This review further highlights the key contribution of experience in the short (behavioural learning) and long term (metabolic learning), including the critical role of fetal environment in shaping feeding behaviour both directly by food cue–consequence pairings and indirectly via modifications of metabolic functioning, with cascading effects on energy balance and body reserves and, consequently, on feeding motivation.