Document Type
Thesis - Open Access
Award Date
2006
Degree Name
Master of Science (MS)
Department / School
Biology and Microbiology
Abstract
Antibiotics are routinely fed as growth promoters to weanling pigs for the past 50 years. However, frequent use of feed antibiotics potentially results in emergence of drug resistance in microbes, which could be transferred to human pathogens and would interfere with the effective use of therapeutic antimicrobials in human medicine. Such health concerns about the use of antibiotics in animal feeds have led to considerable scientific research and debates. Recently, use of antibiotics in animal feeds has been banned in the European Union and would possibly impact US agriculture soon. This study was conducted to understand the molecular mechanisms of growth promotion in weanling pigs in response to use of the antibiotic chlortetracycline in creeper feed and in absence of intestinal microflora. Eighteen half-sib piglets were obtained by cesarean from three healthy sows and were randomly allocated to three different groups Viz. Control, Antibiotics and Gnotobiotics (n=6). The gnotobiotic animals were kept on sterile milk replacer in gnotobiotic units, whereas the control and antibiotic animals were left with two foster mothers until 21days. At weaning, all the pigs were fed sterilized normal pig feed for another 14 days. The experimental animals from the antibiotic group were fed with similar pig feed having chlotetracycline at 50 ppm. Tissue samples from the distal ileum were collected from all animals at 5-weeks of age and were analyzed for differential expression of genes among the three groups using microarrays. The results of the microarray study showed that out of 1172 genes that were differentially expressed (p<0.05), 135 genes (0.0096% of the spotted genes) were significantly different (q<0.1) between the experimental groups. A variety of genes up-regulated in the antibiotic group as compared to the control and gnotobiotic groups were related to immune response, metabolism, DNA replication, cell cycle and cell signaling. This indicates that the antibiotic (chlortetracycline) induced growth promotion is mediated by up-regulation of a variety of biologically important genes. Analysis of the expression levels of Toll-like receptors (TLRs) in the ileum, measured using real-time RT-PCR, showed that TLR5 was significantly more expressed in the gnotobiotic pigs compared to the control and antibiotic groups, whereas TLR4 did not show any significant differences among various groups. Immuno-histochemistry performed on ileal tissue sections using human polyclonal antibodies did not show any significant differences in the expression of TLR2 and TLR9 in the control and antibiotic groups as compared to the gnotobiotic groups. Glycoconjugate composition on the ileal tissues was examined by immunohistochemistry using 23 biotinylated lectins. LEL, Jacalin, PSA, LCA and SNA lectins showed significant differences among three groups in the binding intensities on the dome and villous epithelium and follicles. Ilea] tissues from gnotobiotic piglets expressed significantly weaker lectin binding for many lectins compared to control and antibiotic group piglets. This indicated that except for a very few lectins, use of antibiotics in animal feed as growth promotants did not induce major changes in lectin binding profile of the small intestine. However, this study reveals that the presence of gut microbiota plays an important role in the expression of various carbohydrate moeities on the intestinal epithelium and follicles. The findings of this study throw light on the molecular and biochemical mechanisms involved in growth regulation of weanling pigs in response to feed antibiotics and germ-free conditions. These findings will also help in formulating alternatives for replacing the use of antibiotics as growth promoters in livestock.
Library of Congress Subject Headings
Swine -- Feeding and feeds
Swine -- Growth
Antibiotics in animal nutrition
Drug resistance in microorganisms
Ileum
Gene expression
Format
application/pdf
Number of Pages
131
Publisher
South Dakota State University
Recommended Citation
George, Sajan, "Molecular and Biochemical Changes in the Ileum of Weanling Pigs Fed Antibiotics as Growth Promotant and in Germ-free Conditions" (2006). Electronic Theses and Dissertations. 1263.
https://openprairie.sdstate.edu/etd2/1263