A genetic selection study to determine the effects on egg hatchability and subsequent chick performance of Japanese quail (Coturnix japonica) eggs incubated at 100 F dry bulb temperature (Control, Line C) when compared to other eggs incubated at 102 F (Selected, Line S) was conducted over 10 consecutive generations. Eggs from a randomly mated population (designated as Generation 0) of Japanese quail maintained at the Oregon Agricultural Experiment Station were randomly allocated to two treatment groups (Lines C and S) and incubated at the different temperatures in separate but identical Jamesway 252 machines. On day 14 of incubation all eggs were transferred to a common hatcher (98.5 F). Using family-based selection, the chicks that hatched from the two lines were subsequently used as breeders (25 paired matings per line) and the resulting eggs from each line incubated at their respective temperatures for 10 consecutive generations. Following the 10th generation percent egg fertility and percent hatch of fertile eggs were greater in Line C vs. Line S (p<O.O3 and p<O.0001, respectively). Embryo development time was shortened in Line S by 24 hours and mean 4- or 5- week body weights were greater (p<0.001) in Line S. Ten-day post-hatch mortality increased greatly in Line S vs. Line C after generation 6 (p<0.001) and hen-day egg production decreased after generation 4 in Line S vs. Line C (p<0.0001). The results indicate that embryo development time can be reduced by high temperature incubation, but at the expense of reproductive traits such as egg production, fertility, and hatchability of fertile eggs. / Graduation date: 2005

Hypoxic responses in quail development differ depending upon stage, duration and level of oxygen partial pressure of embryo. Incubation was switched to/from 110mmHg partial pressure (hypoxia), to/from 150mmHg (normoxia) during different stages in development, and control was incubated in normoxia throughout. Hatchability and embryo survival resulted in no hatchlings in continuous hypoxia. Responses to various hypoxic exposures throughout development resulted in recovery/repair of hypoxic damage by hatch. Heart and body mass, beak and toe length, hemoglobin, and hematocrit were measured to determine embryo responses to hypoxia during development at days 10, 15, and hatch. Hypoxia seemed to have the most deleterious effects on eggs in continuous hypoxia. Collectively, data indicate critical developmental windows for hypoxia susceptibility, especially during mid-embryonic development.

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Appetite is a complex behavior which can be influenced by factors within the animal's body as well as the environment around it. Internal factors include hormonal and nutrient concentrations found in the blood stream and subsequent neuropeptide and neurotransmitter signaling in the hypothalamus. External factors, such as high ambient temperature (HAT), can indirectly affect appetite regulation through other neuroendocrine systems such as the hypothalamo-pituitary-adrenal (HPA) axis. Understanding the physiological responses to endogenous factors and HAT exposure in birds will have implications in both the agricultural and biomedical fields. Thus, the purpose of this dissertation research was to explore the hypothalamic molecular mechanisms associated with food intake in broiler type chickens and Japanese quail, and the effect of HAT exposure on food intake in broiler type chickens. Broiler type chickens have undergone intense artificial selection for traits that promote rapid growth, consequently driving them to consume feed incessantly. It is hypothesized that broiler type chickens lack a mechanism that signals satiety, causing them to eat significantly more than layer type chickens. Selection for rapid growth of meat (muscle tissue) has made the broiler more susceptible to the deficits associated with HAT exposure, as animals composed primarily of muscle dissipate less heat while also producing more heat than those composed of fat. The Japanese quail have undergone relatively minor artificial selection compared to the chicken, suggesting that use of this model may provide insight into the mechanisms of appetite regulation in wild-type bird species. This research involved administrating appetite associated factors into the avian brain via an intracerebroventricular (ICV) injection including gastrin releasing peptide, vasoactive intestinal polypeptide, neuropeptide AF, and prostaglandin D2. Additionally, I explored the effects of HAT on food intake, and on the efficacy of several ICV administered appetite associated factors including neuropeptide Y, corticotropin releasing factor and α-melanocyte stimulating hormone. After treatment administration, I measured changes in food intake and behavior, activation of hypothalamic nuclei including the arcuate nucleus, dorsomedial nucleus, lateral hypothalamus, paraventricular nucleus, and the ventromedial nucleus, and the nucleus of the hippocampal commissure. I then measured changes in gene expression in both whole hypothalamic samples and specific hypothalamic nuclei. The data from non-HAT associated studies provided information on the hypothalamic nuclei which respond to the various appetite associated factors and the molecular mechanisms mediating changes in appetite. The data from the HAT study provided information on the hypothalamic nuclei involved in the avian response to HAT exposure, and the molecular mechanisms involved in the effect on food intake. Overall, these data provide insight on the mechanisms associated with short-term regulation of appetite, and pathways associated with stress and food intake. / Doctor of Philosophy / Appetite regulation can be affected by factors both in the body and out in the environment. Understanding how both internal and external factors affect appetite regulation can have positive implications in both the agriculture industry as well as the biomedical field. In agriculture, animals exposed to high ambient temperatures often exhibit several deficits including immunosuppression, decreased body weight, and ultimately an increased risk of mortality. It is hypothesized that the factor linking negative wellbeing to heat exposure is a reduction in food intake. Animals aside, the prevalence of eating disorders has doubled worldwide every 6 years since the year 2000. These numbers have increased even more during the recent COVID-19 pandemic. In order to improve the wellbeing of both humans and animals exposed to stressing stimuli, it is imperative we understand how individual appetite associated factors affect food intake, and how external stressors can impact the normal physiology of the hypothalamus. Thus, the purpose of this dissertation was to elucidate the hypothalamic mechanisms mediating appetite regulation using broiler type chickens and Japanese quail as models. Related pathways and molecular mechanisms were explored for several appetite associated factors including gastrin releasing peptide, vasoactive intestinal polypeptide, neuropeptide AF, and prostaglandin D2. Additionally, the effect of high ambient temperature on food intake, on the efficacy of several appetite associated factors including neuropeptide Y, corticotropin releasing factor and α-melanocyte stimulating hormone, and the hypothalamic pathways and molecular mechanisms mediating heat-induced anorexia were assessed.

Many aspects of biological function are affected by hormones, from physiology to behavior, and the synthesis and release of hormones in vertebrates are regulated by the endocrine axes of control. A growing body of research shows that the mechanisms underlying the endocrine axes of control are complex and interconnected, with many hormones having multiple effects, and with many interactions between axes. In this study, I examined the effects of decreased thyroid function on the glucocorticoid stress response in Japanese quail, a potential interaction between the hypothalamic-pituitary thyroid (HPT) and hypothalamic-pituitary adrenal (HPA) axes of control. I used the thyroid inhibitor ammonium perchlorate (AP) for 2 weeks and 5 weeks to induce two states of decreased thyroid function: a thyroid challenged state, in which birds have depleted thyroidal T4 content, but still maintain euthyroid (normal) concentrations of plasma T4, and a hypothyroid state, in which birds have depleted thyroidal T4 content and decreased concentrations of plasma T4. Thyroid function was assessed by measuring plasma T4 concentrations, thyroidal T4 content, and thyroid gland mass. I took blood samples from birds both immediately prior to and immediately following a 30 minute confinement and agitation stressor to evaluate the effects of decreases in thyroid function on basal and stress-induced plasma corticosterone and plasma T4 concentrations. I found two key results: First, although baseline levels of plasma corticosterone were unchanged, the corticosterone stress response was significantly blunted in both the thyroid challenged and hypothyroid birds as compared to controls. This finding suggests that the HPT and HPA axes are functionally connected in birds, and other evidence suggests this connection is likely at the pituitary or hypothalamic level. Second, in hypothyroid birds, plasma T4 concentrations were elevated (into the euthyroid range) in response to the experimental stressor, although no change in plasma T4 was observed in thyroid challenged or control birds. This finding suggests that plasma T4 may have a permissive role in mounting a stress response. / Master of Science in Life Sciences

The neuroendocrinology of masculine sexual behavior was examined in Japanese quail selected bi-directionally for adult mating frequency. Experiments were conducted with brain tissues from functionally castrated, High (HM) and Low Mating (LM) line quail to compare (1) the in vivo aromatization of ³H-testosterone and (2) cytosolic estradiol-binding by in vitro saturation analyses. After in vivo incubation with ³H-testosterone, all radioactivity recovered in brain tissues was in the form of testosterone, dihydrotestosterone, or estradiol. Neither the total ³H nor ³H-testosterone metabolite radioactivity differed upon comparison of the two genetic lines. Of all ³H-testosterone metabolite radioactivity, ³H-estradiol represented 45 ± 6% in the HM line and 46 ± 6% in the LM line, indicating that the line difference in mating frequency was not due to a corresponding difference in aromatase activity. Inasmuch as both the HM and LM line birds actively converted testosterone to estradiol, these results implicated a neural mechanism involving estradiol-receptor interactions. Estradiol-receptor binding parameters were estimated in subsequent experiments by fitting a hyperbolic saturation curve to point measurements of total binding. Using this single-class binding site model, the apparent dissociation constant (K_d) for the estradiol-receptor interaction in the HM line was 0.40 ± .06 nM and the number of specific estradiol binding sites (B_max) was 10.4±.4 fmoles/mg cytosol protein. For the LM line, an apparent Kd of 0.41 ± .20 nM and a B<max> of 9.50 ± 1.0 fmoles/mg cytosol protein were obtained. The similarity between corresponding binding parameters for the divergent mating lines indicated that the number and/or estradiol-binding affinity of a single class of cytosol receptors was also not responsible for the line difference in mating frequency. Though these results confirm that interaction of estradiol with cytosol receptors was not the limiting neuroendocrinological mechanism in the differential expression of masculine sexual behavior in quail, the possible involvement of dynamic interrelationships between cytoplasmic and nuclear estrogen binding was discussed. / Ph. D.

Adrenal corticosterone and aldosterone content, body weight changes and serum osmolality were examined during water restriction and water deprivation. Progressive water deprivation resulted in increased serum osmolality and decreased body weight; adrenal aldosterone content did not change. Adrenal corticosterone content tended to be elevated during early water deprivation indicating a stress response, but tended to decrease after seven days of water deprivation suggesting adrenal fatigue. During water restriction, after the period of weight loss, adrenal elevated corticosterone content and serum osmolality were elevated. As the birds began to gain weight aldosterone did not change, but adrenal corticosterone content and serum osmolality approached control values, suggesting the birds were beginning to adapt to the water restriction. The lack of an aldosterone response suggests that high sodium in the diet was more important than the water regimes in regulating aldosterone. The adrenal was sensitive to ACTH as indicated by the elevated adrenal aldosterone and corticosterone content after ACTH injection, however sodium status probably affects the aldosterone response to ACTH. / Master of Science