|Allee, Gary - UNIVERSITY OF MISSOURI|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: April 15, 2009
Publication Date: May 15, 2009
Citation: Carroll, J.A., Allee, G.L. 2009. Hormonal control of feed intake in swine. In: Torrallardona, D., Roura, E., editors. Voluntary feed intake in pigs. Wageningen Academic Publishers. p. 155-187. Interpretive Summary: Under normal circumstances, the regulation of feed intake is a complex, albeit finely orchestrated, biological process that involves multiple biochemical pathways, physiological processes, and physical constraints within the body. Even minor disruptions to this finely tuned process can manifest themselves as phenotypic characteristics such as those associated with obesity and anorexia in humans. Even in an ideal nutritional environment, complications associated with adequate food consumption and appropriate nutrient intake becomes a complicated process regulated by psychological, sociological, physical, environmental, and physiological inputs. In livestock production, however, feed intake is largely controlled through management practices that strive to optimize the economic balance between food intake and overall animal health and productivity. For the most part, maintaining this balance in mature animals is less complex than that associated with young, growing animals, as mature animals are typically retained in livestock production settings for reproductive and lactation purposes. The ability to effectively control feed intake during critical periods of development within livestock production systems will undoubtedly come to pass as scientists continue to elucidate the complex and multifaceted pathways that regulate feed intake and develop novel approaches to manipulate these systems in a beneficial manner. The economic importance associated with achieving optimal feed intake associated with growth, health, and reproduction will continue to drive research directed at understanding and conquering this complex system. This chapter highlights important research that has explored various opportunities for stimulating feed intake in swine with primary emphasis on newly weaned pigs.
Technical Abstract: Voluntary feed intake is controlled by a plethora of factors including, but not limited to, day length, social interactions, environmental conditions, oronasal sensory cues (i.e., taste, smell, texture), gastrointestinal fill, health status, metabolic status, dietary composition, drug interactions, exercise (physical activity), mental status (i.e., depression), and gender. However, most, if not all, of these factors can mediate the hormonal milieu within the body that can ultimately control feeding behavior. Therefore, the focus of this chapter will be on hormonal control of voluntary feed intake in swine. For detailed information pertaining to other factors that affect voluntary feed intake in swine such as perinatal flavor programming, oronasal chemosensory cues, metabolism, antinutritional factors, social interactions, environmental conditions, and pathogen exposure, the reader is referred to the accompanying chapters within this book. With regard to hormonal regulation, voluntary feed intake is controlled by intricate and diverse afferent and efferent communication pathways that transmit hormonal and neural messages throughout the body that ultimately reflect the status of the body’s energy balance to the hypothalamus. Collectively, these signals are responsible for coordinating a delicate balance between energy utilization and energy intake in order to maintain energy homeostasis. Some of these biological messages, such as glucose and cholecystokinin, tend to be more reflective of short-term energy balances associated with food consumption, whereas others, such as insulin and leptin, tend to be more reflective of long-term energy stores within the body. While numerous hormones have been shown to be involved in feed intake, this chapter will focus on hormones associated with the control of feed intake, specifically in swine, with supporting information generated in other species. Specifically, information will be provided on the relationship between feed intake and the somatotrophic axis, the appetite stimulating affects of ghrelin, orexin, neuropeptide Y (NPY) and agouti-related protein (AGRP), and the appetite suppressive effects of leptin and urocortin. Additionally, information will be presented related to the potential effects of glucocorticoids on appetite stimulation in swine.