Sheep as a model for control of appetite and energy expenditure

There has been a world‐wide increase in the incidence of obesity over the last 2‐3 decades, which has generated a great deal of interest in how the brain controls food intake and body weight. It is widely recognised that a number of peripheral hormones and metabolic substrates act within the brain to regulate energy balance. Energy balance is determined by food intake and the rate of energy expenditure. The neural pathways that regulate food intake are known to exert reciprocal control to regulate energy expenditure and this dual control is the focus of this chapter. To date, rodent models, especially mice, have primarily been used to study this phenomenon, because of the ease of performing genetic manipulations. Nevertheless, numerous large‐animal models have provided valuable insights into the neural control of body‐weight. This review will largely focus on the sheep as a model for the study of neuroendocrine regulation of food intake, energy balance and adiposity. Various models have been developed in this species to characterise the control of body weight, including systems for diet manipulation, identification of inherent differences in the predisposition to gain weight and models based on quantitative genetics and selective breeding.