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No description available.

No description available.

No description available.

This study was undertaken to evaluate shear, bending, and torsion test procedures on the radius, ulna, humerus, femur, tibia, and tarsometatarsus of 72 week old caged layers. Shear and bending properties were determined to evaluate the effects of juvenile protein feeding sequence, body size, and cage profile on the strength of these bones. Body size affected (P < 0.05) the ultimate shear forces of the femur, tibia, and tarsometatarsus. The ultimate bending force and shear modulus of the tibia were also influenced by body weight (P < 0. 05). Juvenile protein sequence and body weight affected the torque and torsional shear stress of the tibia. No differences were noted in shear and bending strength when bone geometry as well as force was considered. The frequency pattern of the bending fractures occurring in the radius, ulna, femur, and tibia were influenced by juvenile protein feeding sequence (P < 0.05). The bones from the control birds failed in bending due predominantly to a weakness of tensile stresses. The reversal in protein caused the bones to fail due to a combination of tensile and shear stresses. The torsion test of the tibia and radius showed. the failure pattern to follow a 45 degree helix around the diaphysis of the bone which is indicative of tensile failures. The four point bending test was not desireable for determining the modulus of elasticity of poultry bones with a length to diameter ratio less than 10. No correlations were found between shear and bending properties of any of the bones. Similarly, the shear, bending, and torsion properties of the tibia were not related. / Ph. D.

Studies were conducted to investigate the fermentation and nutritive value of ensiled broiler litter and corn forage. The non-processed broiler litter, containing a wood shaving base, contained 82.9% DM, 26.8% crude protein, 23.0% crude fiber and 16.7% ash. Corn forage was harvested at two stages of maturity, corresponding to 26 and 38% DM. Two studies, one designated "small-bag" and one designated "large-bag" were conducted. For the small-bag study the treatments at each maturity were: untreated; urea, 0.5%, wet basis; and litter at levels estimated to contribute 15, 30 and 45% of the total dry matter. For these, mixtures were mixed by hand in 2 kg amounts and packed into small polyethylene bags supported in cardboard food containers. For the large-bag study the treatments at reach maturity were: untreated; urea, 0.5%, wet basis; and levels of litter to contribute 15 and 30% of the total dry matter. The large-bag silages were mixed with shovels and ensiled in large polyethylene bags containing approximately 114 kg per bag. Both the small-bag and the large-bag silages were evaluated on the basis of nutrient composition and characteristics of fermentations such as pH and organic acid concentration. Total bacteria and coliform counts were conducted on the small-bag silages to evaluate fermentation as a means of destroying microorganisms present in litter. The large-bag silages were fed to sheep in two metabolism trials and two palatability trials to study the digestibility, nitrogen utilization and voluntary intake of the ensiled mixtures. The addition of broiler litter resulted in significant increases (P < .01) in dry matter, crude protein and ash for silages made from forage harvested at both maturities. Litter increased the crude protein from about 8% (dry basis) for the control treatment to about 11, 15 and 18%, respectively, for silages in which litter contributed 15, 30 and 45% of the total dry matter. Ammonia concentrations of silage were increased (P < .01) by each level of litter. Litter and urea appeared to buffer the organic acids of fermentation resulting in final concentrations of lactic acid that were higher than control silages. Total bacteria numbers were in excess of 3 million per gram; however, only the highest level of litter in maturity 2 silages and the two highest levels of litter in maturity 2 silages had significantly higher counts than controls. Coliforms were no higher in litter silages than controls. When fed to sheep, dry matter digestibility was similar for all silages. Crude protein digestibility was depressed by advancing maturity of the corn plant, but significantly increased by each level of litter. Nitrogen retention data indicated that litter nitrogen was well utilized; however, increasing the level of litter from 15 to 30% of the dry matter depressed efficiency of dietary nitrogen utilization. Dry matter intake was significantly greater (P < .01) for silages containing litter than for control and urea silages. There were no significant differences in dry matter intake associated with forage maturity. / Ph. D.

In order to determine the feasibility of using the laying hen as a source of molybdenum containing eggs, a dose response experiment was conducted which involved the feeding of graded levels of molybdenum to White Rock laying hens. The feeding of 2000 ppm of molybdenum resulted in decreases in egg production and hen weight. Only egg production was decreased at 1000 ppm of molybdenum. The 500 ppm level of supplementation appeared to be most applicable to further studies in that little effect on either hen weight or egg production was noted. It was also observed that at this level the egg concentration of molybdenum plateaued at 16.4 ppm after 14 days of feeding the experimental ration. An experiment designed to assess the toxicity of the molybdenum included in the egg by the laying hen to the developing chick embryo permitted the estimation of the L.D.₁₀₀ to be about 17 ppm of molybdenum. This value agrees quite closely to the L.D.₁₀₀ of yolk sac injected molybdenum. The embryonic death response observed in this experiment did not occur during any specific period of development. Succinoxidase assays conducted to study the death response indicated that there was no difference in succinoxidase. It was further noted that there was a decline in lethal response in embryos from hens fed the molybdenum containing ration for periods in excess of three months. This decline was mediated by a decreased concentration of molybdenum in the eggs from these hens. The mode of inclusion of molybdenum in the egg, by the laying hen was studied. It appeared that the majority of the molybdenum is included during the maturation of the ova in the ovary. The high concentration of molybdenum observed in the uterus suggests that the shell be considered in future studies. A chemical fractionation of the eggs from the hens fed the molybdenum containing diet indicated that very little of the molybdenum was present in the lipid fraction. Twenty-five percent of the total egg molybdenum was found to be associated with the protein fraction. A rat assay coupled with further chemical procedures indicated that the molybdenum to protein bonding was not of a covalent nature. The observation of n growth depression in chicks which had been injected with molybdenum during their embryonic development was not corroborated by a more extensive study. Although this study was confounded by the possible existence of a copper deficiency, some evidence was obtained for the involvement of molybdenum in the copper metabolism of the chicks. It was surprising that no increase in the blood and liver molybdenum concentrations was observed when the diets containing either 500 or 1000 ppm of molybdenum were compared. The blood and liver copper concentrations were little affected by molybdenum supplementation. / Ph. D.

Experiments were conducted to explore physiological, pathological, and immunological aspects of stress in chickens. Mechanisms of habituation and their association with adrenal steroids were also studied. Degree of stress experienced during perinatal and neonatal stages was evaluated. In both stages, heterophilia and lymphopenia were noted and post-hatching heterophil to lymphocyte (H/L) ratios declined in a quadratic manner with age. Feed restriction elicited a similar stress response, as indicated by H/L ratios in dwarfs and normals with the effect of adapting to fasting having dissipated between 12 to 16 days. Resistance to Eimeria tenella infection was greater in normals than dwarfs, and for fasted than ad libitum fed chicks. Neither genotype nor feeding regimen had an effect on antibody response to SRBC. Frustration induced by thwarting of feeding resulted in a dramatic elevation in HIL ratios and conspicuous behavioral responses, suggesting responses to fasting may be physiologically and psychologically modulated. Provision of sand during feed withdrawal attenuated physiological responses, possibly via alteration of psychogenic components. An experiment was designed to evaluate the impact of mild feed restriction at several ages on heat tolerance. Normal chicks feed-deprived during the neonatal stage had lower H/L ratios, improved resistance to marble spleen disease and growth during heat treatment than those fed ad libitum or fasted at older ages. A companion experiment examined habituation and concomitantly the role of glucocorticoids in stress response. Neonatal fasting-induced stress responses without concurrent increases in adrenal steroidogenesis did not enhance ability of normal chicks to withstand high ambient temperatures. The hypothesis regarding modulatory roles of corticosteroids in neonatally-elicited adaptation was affirmed in a subsequent study. Feed withdrawal for 8 or 24 h at 36 days of age did not induce either H/L or plasma corticosterone response of chicks stressed early in life. In contrast, neither criterion provided evidence for adaptation to feed deprivation by neonates treated with an adrenal steroidogenesis blocker during the fast. corticosterone mediated inhibitory feedback regulation of the hypothalamic - pituitary - adrenal axis which down-regulates ACTH response was also evident. / Ph. D.

Five experiments were conducted to investigate the effects of early feed restriction on body weights, feed conversion, organ weights, fat deposition, carcass and muscle composition, plasma lipids, lipogenesis, lipolysis, and muscle tissue DNA and RNA in broiler chickens. In Experiments 1 and 2, broiler chicks were reared in litter pens for 49 days, while Experiments 3,4, and 5 were conducted in battery cages for 28 days. Feed restriction in all experiments was induced by providing male broiler chicks with 40 kcal/bird/day for 7 (Experiments 1 and 2) or 6 (Experiments 3, 4, and 5) days, starting at 4 days of age. Feed restriction (40 kcal/bird/day) for broiler females in Experiment 1 was imposed from 4 to 9 days of age. Ad libitum feeding was resumed after the restriction periods and continued to the conclusion of each experiment. Broilers fed ad libitum for the entire experimental period were used as controls in each study. Broilers under early feed restriction had significantly (P s .05) lower mean body weights than ad libitum fed controls, for all ages measured. However, feed to gain ratios for restricted birds were Significantly lower at 28 (Experiments 1 through 4) and 49 (Experiments 1 and 2) days of age than for birds fed ad libitum. Total pen body weights for restricted and ad libitum fed groups were similar at 49 days of age in Experiments 1 and 2 which, reflected a significant reduction in the rate of mortality observed in the early restricted groups. Significantly higher levels of lipogenic activity, plasma triglycerides and lipoproteins (VLDL + LDL), and significantly larger abdominal fat pads were observed in restricted broilers than in ad libitum fed controls at 28 days of age (Experiment 4). No significant differences were found in organ weights, carcass composition, lipolysis, and muscle tissue DNA/RNA levels, and muscle composition between early restricted and unrestricted broilers. Results from these studies indicate that restricted broilers were not able to attain body weights comparable to ad libitum fed birds at 49 days of age. In contrast, early feed restriction resulted in consistently better feed efficiency in restricted birds when compared to controls. Furthermore, it appears that early feed restriction altered lipid metabolism early in life; however, organ weights, fat deposition, muscle composition, and carcass composition were only minimally affected by this procedure. / Ph. D.

The present set of experiments were designed to examine the role of histamine, and its interaction with corticotropin releasing factor (CRF) and bombesin (BM) in food intake regulation of chickens. The hypothesis being tested was as follows: One component of the neuroregulation of food intake involves histaminergic activity in the hypothalamus, acting on either H1 or H2 receptors, how these receptors interact with CRF neurons and if BM elicits its effects on feeding through CRF release. Single Comb White Leghorn (SCWL) and broiler cockerels were utilized for these experiments. Birds were stereotaxically implanted with a 23-gauge thin-walled stainless steel guide cannula, and were provided a mash diet and water for ad libitum consumption. All compounds were infused into the right lateral ventricle. Effects were monitored at 15-minute intervals through three hours postinjection. Experiment 1 examined the effects of intracereboventricular (ICV) injections of histamine (HA) and two HA antagonists, the H1 receptor antagonist chloropheneramine maleate (CM) and H2 receptor antagonist cimetidine (CIM), on food and water consumption and body temperature. Histamine was infused using 0, 25, 50, and 100 µg per 10 µl of artificial cerebrospinal fluid (aCSF). Histamine significantly decreased food and water consumption (P< 0.05) over the three hour observation period in a dose-dependent manner. Histamine was then infused to observe if the decrease in water intake was dependent upon the decrease in food intake. Birds were not allowed access to feed during this experiment. Water intake was not affected by HA in either SCWL or broilers when food was not available. To observe the effects of HA on thermoregulation, HA was infused using the same dosages and body temperature recorded for three hours. Histamine produced hypothermia at a dose of 25 µg in SCWL cockerels, with a quadratic trend at 165 and 180 min. Broiler cockerels did not show hypothermia, but rather a constant hyperthermia compared to the control with a quadratic trend throughout the latter part of the experiment. The last phase of the first set of experiments, birds were pretreated with either CM or CIM (100 µg/10 µl aCSF) followed by HA. When the birds were pretreated with either CM or CIM, the hypophagic responses to HA were attenuated. The pair of experiments that utilized H1 and H2 receptors demonstrated that these receptors are involved in the neural regulation of food intake. These experiments also demonstrated that the aphagic effects of HA on food intake can be blocked with the pretreatment of antihistaminics affecting both H1 and H2 receptors. In Experiment 2, studies were conducted to determine if neuronal CRF elicited its effects on feeding through the release of HA. Birds were infused with 0 or 20 µg CRF and either 0 or 100 µg of CM or CIM. CRF decreased food and water intake in both SCWL and broiler cockerels. When birds were pretreated with CM, the hypophagic responses to CRF were attenuated. When birds were pretreated with CIM, the hypophagic responses of CRF were attenuated in broiler cockerels; this response was not seen in SCWL cockerels. Water intake followed a similar pattern. It was concluded that, contrary to studies showing that HA causes the release of CRF in other species, CRF may cause the release of HA in chickens. Experiment 3 was designed to investigate whether bombesin (BM) elicited its effects on feeding through the release of CRF. Birds were infused with either, 0 or 0.5 µg BM, 0 or 5 µg aCRF (9-41) (CRF antagonist), or a combination of both. These compounds were infused to test whether the effects of BM could be blocked with the pretreatment of anticorticotropics. Food and water consumption were significantly decreased (P< 0.05) with the infusion of BM in both SCWL and broiler cockerels. Food intake was not affected with the infusion of aCRF in SCWL or broilers cockerels. However, water consumption was increased when birds were given ICV injections of aCRF. When birds were pretreated with aCRF, the anorexigenic and adipsic effects of BM were attenuated. It was concluded that BM elicits its effects on feeding through the release of CRF. These results also demonstrate that the aphagic effects of BM could be blocked with the pretreatment of anticorticotropics. / Master of Science