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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.

The fact that sensory modalities do not become functional at the same time raises the question of how sensory systems and their particular experiential histories might influence one another. Few studies have addressed how modified stimulation to earlier-emerging modalities might influence the functioning of relatively later-developing modalities. Previous findings have shown that enhanced prenatal tactile and vestibular (proximal) stimulation extended and delayed normal patterns of auditory and visual responsiveness to species-typical maternal cues in bobwhite quail respectively. Although these results were attributed to the increased amount of sensory stimulation, these results may be a function of when prenatal augmented proximal exposure took place. To address this issue the present study exposed groups of bobwhite quail embryos to equivalent amounts of augmented tactile and vestibular stimulation either at a time when a later-emerging modality (auditory or visual) was beginning to functionally emerge or when it had already functionally emerged. Results indicate that differences in the timing of augmented tactile and vestibular stimulation led to differences in subsequent auditory and visual responsiveness. Embryos were unable to learn a maternal call prior to hatching when enhanced proximal stimulation coincided with auditory functional emergence implicating a deficit in auditory functioning, but did learn a maternal call when enhanced proximal stimulation occurred after auditory functional emergence. Augmented proximal stimulation that coincided with visual functional emergence did not appear to influence normal visual responsiveness, but when proximal stimulation occurred after visual emergence, chicks displayed an accelerated approach response to species-typical visual cues. These findings support the view that the timing of enhanced stimulation to earlier-emerging modalities is important, and have meaningful implications for intersensory theory and research. / Ph. D.

Early perceptual learning capacity has been shown to correspond with the relative status of emergent sensory systems throughout prenatal and postnatal development. It has also been shown that young infants can learn perceptual information during perinatal development. However, the exact nature of the relationship between prenatal and postnatal perceptual development and the role of early experience on learning ability have yet to be examined. The present study examined how auditory learning capacity in bobwhite quail chicks is affected by the interrelationship between the developing auditory and visual systems in late prenatal/early postnatal development. Chicks were provided with auditory information during the period immediately prior to or the period following hatching. In addition, visual experience was either provided or attenuated during both the prenatal and postnatal periods. Findings revealed that chicks postnatally exposed to 10 min/hr of maternal auditory stimulation in lighted conditions required 72 hr exposure to the call in order to learn that bobwhite maternal call (Experiments 1A and 1B). Control chicks who experienced the prenatal egg-opening procedure demonstrated no naive preference for two individual variants of the bobwhite maternal assembly call (Experiment 2). However, embryos who received 10 min/hr of prenatal visual stimulation, or who were reared in prenatal darkness successfully learned a maternal call with only 24 hr of postnatal exposure (Experiments 3A and 3C). Embryos who received prenatal visual and postnatal darkened rearing conditions (a mismatch between prenatal and postnatal experience) showed deficits in postnatal auditory learning (Experiment 3B). Embryos who were exposed to 10 min/hr of prenatal maternal auditory stimulation and 10 min/hr of nonconcurrent visual stimulation remembered the maternal call into later ages of postnatal development than in previous studies when reared in lighted or darkened postnatal conditions (Experiments 4A and 4B). However, when all prenatal and postnatal visual experience were both removed from embryos' and chicks' environments, deficits in prenatal auditory learning and postnatal memory were observed (Experiment 4C). These results indicate that prenatal and postnatal learning in bobwhite quail occur differently, that mismatches in prenatal and postnatal experience interfere with postnatal auditory learning, and that prenatal learning and postnatal memory are affected by the amount of visual stimulation present within chicks' environmental milieu. In the broader scheme, these results provide further evidence that the auditory and visual systems are linked during early development and support an ecological perspective of learning and memory. / Ph. D.

Prenatal sensory stimulation can have facilitative or interfering effects upon subsequent perceptual learning and development in bobwhite quail. Exposure to moderate amounts of unimodal prenatal sensory stimulation has been shown to accelerate early intersensory responsiveness, while exposure to concurrent prenatal bimodal sensory stimulation has been shown to interfere with perceptual learning and development. An immediate mechanism that may underlie this developmental intersensory interference is the arousal level of the organism associated with exposure to prenatal bimodal stimulation. Concurrent bimodal stimulation is known to elicit significantly higher levels of behavioral arousal and heart rate in bobwhite quail embryos. This study investigated the possibility that increased arousal associated with prenatal bimodal stimulation could have enduring effects upon subsequent postnatal behavioral organization and perceptual abilities in bobwhite quail. Subjects were exposed to one of three prenatal stimulation regimes: (a) concurrent bimodal (auditory/visual) stimulation, (b) unimodal auditory stimulation, or (c) no supplemental stimulation. Chicks exposed to concurrent prenatal bimodal stimulation demonstrated significantly greater levels of behavioral activity as well as decreased social behavior in the open-field when compared to unimodal auditory subjects and controls. Additionally, prenatal bimodal exposure may have led to a failure to utilize multimodal maternal cues in determining species-specific perceptual preferences in the days following hatching. All exposure groups demonstrated postnatal auditory learning of a maternal call, thus no interference effect was found for concurrent prenatal bimodal stimulation on postnatal auditory learning. These results suggest that concurrent prenatal bimodal stimulation has enduring effects upon postnatal behavioral arousal that may impact perceptual responsiveness of bobwhite quail in the days following hatching. / Ph. D.

Previous research has demonstrated that augmented prenatal sensory stimulation can influence the emergence of normal or species-typical patterns of intersensory perception. For example, unusually early visual experience can produce a facilitative effect on subsequent postnatal perceptual responsiveness, while substantially augmented prenatal visual stimulation can interfere with early postnatal responsiveness. In constructing a link between early experience and neuronal plasticity, it has been established that unusual visual experience can produce measurable changes in post-synaptic structures, particularly dendritic morphology, in brain areas responsible for vision. In avian species, the brain area responsible for vision is the visual Wulst, thought to be analogous to the mammalian visual cortex. This study examined the effects of differing amounts of augmented prenatal visual stimulation on the plasticity of neurons in the visual Wulst and on subsequent postnatal visual responsiveness to maternal cues in bobwhite quail chicks. Results revealed that the pattern of neuronal organization and postnatal behavior was influenced by the amount of prenatal visual experience subjects were provided. Specifically, chicks exposed to 240 min of prenatal visual stimulation during the last 24 hr prior to hatching had neurons with significantly fewer spines/10 mm dendrite and displayed accelerated patterns of species-typical visual responsiveness. In contrast, chicks provided 900 min of prenatal visual stimulation had more complex neurons (including more spines, longer dendrites, and more branches) and failed to display normal species-specific visual responsiveness in the days following hatching. These results suggest that neuronal organization in the bobwhite Wulst proceeds in a selective fashion, molded by experience, and appears to influence early perceptual development and organization during the perinatal period / Ph. D.

The effect of dietary fats on reproductive performance, egg quality, fatty acid composition of tissues and egg yolk, and prostaglandin levels in embryonic tissues in Japanese quail (Coturnix, coturnix japonica) were evaluated. The addition of 5.0% chicken fat (CHX), hydrogenated soybean oil (HSBO), menhaden fish oil (MENH) or soybean oil (SBO) to the maternal and paternal diet altered tissue and yolk composition of the hens and tissue composition of the males to reflect the dietary source. Comparisons were made to chicken fat which served as a control. Feeding MENH increased the omega three fatty acid concentrations in liver, heart, testicle, and yolk. Feeding HSBO and SBO increased the omega six fatty acid concentrations in yolk. Feeding MENH and SBO increased the total monosaturated fatty acids in yolk. The concentrations of polyunsaturated fatty acids were increased by feeding MENH and SBO. Feeding MENH decreased egg production. Feeding MENH and HSBO decreased hatchability. Feeding MENH decreased specific gravity of eggs at day 30, 60, and 90. Feeding CHX increased specific gravity at day 30, 60 and 120. In addition, feeding CHX increased chick weight. Feeding SBO decreased early embryonic death. There were no consistent differences noted in tissue prostaglandin levels of embryos from hens on the differing diets. / Master of Science