Feeding behavior is a complex trait that is regulated by various hypothalamic neuropeptides and neuronal populations (nuclei). Understanding the physiological regulation of food intake is important for improving nutrient utilization efficiency in agricultural species and for understanding and treating eating disorders. Knowledge about appetite in birds has agricultural and biomedical relevance and provides evolutionary perspective. I thus investigated hypothalamic molecular mechanisms associated with appetite in broilers, layers, chicken lines selected for low (LWS) or high (HWS) body weight, and Japanese quail, which provide a unique perspective to understanding appetite. Broiler-type chicks have been genetically selected for rapid growth and consume much more feed than do layer-type chicks which have been selected for egg production. Long-term selection has caused the LWS chicks to have different severities of anorexia while the HWS chicks become obese, thus making these lines a valuable model for metabolic disorders. Lastly, the Japanese quail have not undergone as extensive artificial selection as the chicken, thus this model may provide insights on how human intervention has changed the mechanisms that regulate feeding behavior in birds. This research involved applying a variety of different treatments including fasting and refeeding, diets differing in macronutrient composition, and/or central administration of neuropeptide Y, xenopsin, neuropeptide K, oxytocin, mesotocin, gonadotropin-inhibitory hormone, and prolactin-releasing peptide, after which I measured feeding behavior and various aspects of hypothalamic physiology. I measured nuclei activation in hypothalamic appetite-associated regions including the lateral hypothalamus, paraventricular nucleus, ventromedial hypothalamus, dorsomedial nucleus, and arcuate nucleus and I measured gene expression of various appetite-associated factors in the whole hypothalamus and individual nuclei. These data provided information about the regions of the brain involved in mediating effects on appetite and the molecular pathways involved in the effect on appetite. There were differences in dose threshold sensitivity to various injected factors in the different stocks, differential responses to fasting and refeeding, and differences in nuclei and genes that were activated in response to the various treatments. These data provide valuable insights on the molecular mechanisms that are associated with the short-term regulation of feeding behavior and pathways that may be genetically stock-dependent. / PHD / Poultry production and welfare may be enhanced by regulating food intake of chickens during specific stages of growth, resulting in improved nutrient utilization efficiency. For example, broiler breeders are feed restricted to achieve target weights in order to prevent obesity and other disorders and improve performance. To affect the appetite of chickens, an understanding of the neural mechanisms mediating food intake is needed but there is a lack of information in this area. Thus, the purpose of this dissertation was to elucidate some of these mechanisms that control appetite regulation in poultry using chickens and quail as models. Several neuropeptide-associated pathways were studied and appetite-related molecular mechanisms were elucidated for neuropeptides K and Y, oxytocin, mesotocin, gonadotropin-inhibitory hormone, prolactin-releasing peptide, xenopsin, different macronutrient composition diets, and fasting and refeeding.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/95888 |
| Date | 06 June 2018 |
| Creators | McConn, Betty Renee |
| Contributors | Animal and Poultry Sciences, Cline, Mark A., Kuenzel, Wayne J., Siegel, Paul B., Gilbert, Elizabeth R., Denbow, D. Michael |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
Page generated in 0.0015 seconds