Browsing by Author "Caldwell, David J."
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- Effects of Incubation Temperature and Transportation Stress on Yolk Utilization, Small Intestine Development, and Post-Hatch Performance of High-Yield Broiler ChicksBarri, Adriana (Virginia Tech, 2008-11-21)Growth and performance parameters of broiler chicks depend on adequate development of the small intestine. Stressors such as elevated or decreased temperatures during incubation and post-hatch transportation may have an effect on the gastrointestinal development of the broiler chick. The objective of the first study was to investigate the effects of elevated embryonic incubation temperature (IT) on post-hatch relative nutrient transporter gene expression, integrity of the intestinal epithelium, organ development, and performance in Ross 308 broiler chickens. Nine hundred fertile eggs were incubated at different egg-shell temperatures during development. Body weights and performance parameters were measured at day of hatch (DOH), d 7, 14, 21, 30, and 42. Small intestine and residual yolk were collected at DOH, d 2, 4, 6, and 10 and weighed individually. The small intestine was evaluated for mucosal morphology measurements and relative nutrient transporter (SGLT1, GLUT2, GLUT5, EAAT3, and PepT1) gene expression. The objective of the second study was to evaluate the effects of embryonic incubation, simulating a multi-stage incubation system, and post-hatch transportation temperatures on post-hatch performance, yolk free body weights, relative nutrient transporter gene expression, yolk utilization, intestinal morphology, and organ development of broiler chickens. Cobb 500 eggs (n=5200) were incubated with egg-shell temperatures, which were combined depending on the early and late development incubation periods as found in multi-stage incubators: Low (L): 36.7°C, Standard (S): 37.5°C, and High (H): 39°C. After hatch, chicks were further separated into 2 transportation groups: control (C; 34°C), and heat-stressed (D; 40°C). The eight resulting experimental groups were: LS-C, SS-C, LH-C, SH-C, LS-D, SS-D, LH-D, and SH-D. Three and two way interactions (P<0.05) were observed and discussed in both studies for all the parameters analyzed. These studies present for the first time the effects of altered embryonic IT and stress during transportation of newly hatched chicks, on small intestine morphology, digestive organ development, and expression of nutrient transporters mRNA in high-yield broiler chicks. These results contribute to the understanding of mechanisms by which either low or high temperatures, as compared to standard recommendations, during incubation and transportation can affect embryonic development and subsequent performance of broiler chicks.
- Intestinal Mucosal Mast Cell Immune Response and Pathogenesis of Two Eimeria Acervulina Isolates in Broiler ChickensMorris, Bruce C. (Virginia Tech, 2002-12-05)Five experiments were conducted comparing differential intestinal immune responses to two isolates of Eimeria acervulina (EA), EA1 and EA2. In three experiments, broiler chicks were divided into control (non-challenged), EA1, or EA2 challenged (14 days of age) groups. On day 6 post-challenge (PC), changes in body weight were determined, intestinal lesions were scored, and duodenal tissue was evaluated for morphometric alterations and mucosal mast cell responses. EA1 produced duodenal lesions and reduced villus height to crypt depth ratios when compared to controls; however, no differences were found in mast cell counts. EA2 produced differing results, and observed data were suggestive of an intestinal secretory response when compared to EA1 or controls. In Experiment 4, tissues were analyzed from day 2 through day 6 PC. Villus atrophy and crypt hyperplasia were heightened on day 5 PC in both challenged groups. Mast cell counts were significantly greater on days 3 and 4 PC in EA1 birds. In Experiment 5, EA2 oocysts were cleaned with 5.25% sodium hypochlorite to evaluate the possibility of a bacterial contaminant contributing to the pathogenesis of intestinal alterations. Weight gains were decreased by challenge and villus heights and crypt depths were significantly altered in challenged birds, resulting in lower villus to crypt ratios, however, there were no differences in mast cell number. These data are indicative of differential host response and immunovariability between different isolates of the same Eimeria species and are suggestive of mast cell involvement in coccidial immunity in broiler chickens.