Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design


Animal and Nutritional Sciences

Committee Chair

Stanley M. Hileman.


Nutrition and reproduction are linked in that the nutritional status of an individual influences its reproductive performance, i.e. an individual in negative energy balance will have decreased ability to reproduce. The mechanisms in which nutrition influences reproduction are not understood. My data suggest that reductions in lutenizing hormone secretion resulting from photoperiod-induced increases in sensitivity to testosterone negative feedback may be mediated, at least in part, by elevated neuropeptide Y (NPY), a hypothalamic neuropeptide shown to alter gonadotropin releasing hormone release and potently affect food intake. The results from my second study support our hypothesis that the growth hormone mediated hormone, insulin like growth factor-1 (IGF-1) increases thyroid hormone levels during food deprivation. Furthermore, results from these experiments show that food deprivation has a greater impact on males than females and that the thyroid hormone response to IGF-1 during food deprivation is much greater in females. Though there are likely many humoral and neuroendocrine factors that must act together to coordinate the reproductive response to nutrition, our studies with NPY and IGF-1 have begun to examine some potential mechanisms linking nutrition and neuroendocrine control of reproduction in the sheep.