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dc.contributor.authorForrest, James Walteren
dc.date.accessioned2014-03-14T20:37:34Zen
dc.date.available2014-03-14T20:37:34Zen
dc.date.issued2003-05-16en
dc.identifier.otheretd-05192003-133446en
dc.identifier.urihttp://hdl.handle.net/10919/32980en
dc.description.abstractRapid rearing of dairy heifers during late prepuberty has been linked to impairments in mammary development and reductions in milk yield. Our objective was to determine how varying energy intakes between 2 and 14 wk of age affect mammary parenchymal development. At 2 wk of age, Holstein calves were assigned to 1 of 4 treatments (HH, HL, LH, and LL) with 2 levels of energy intake (High or Low) and 2 periods of growth (2 to 8 and 8 to 14 wk of age). At 14 wk, parenchyma at the stromal interface, mid-gland, and above the cistern were collected, fixed, and embedded in paraffin. Digital images of stained sections were used to determine tissue composition (% epithelium, lumen, and stroma). Immunochemistry revealed estrogen receptor (ER) and Ki67 (nuclear proliferation antigen) positive cells, type IV collagen, fibronectin (FN), and laminin. Images representing 4 increasing grades were used to quantify ECM protein deposition. Lumenal and stromal areas were 3.5 ± 1.4% higher (p<0.01) and 4.0 ± 1.7% lower (p<0.01), respectively, in HH and HL heifers. Ki67 labeling in terminal ductular units and subtending ducts was 2.1 ± 0.8% (p<0.01) and 1.4 ± 0.7% (p<0.05) lower for the same feeding level combination. FN deposition was also increased (p<0.05) in HH and HL heifers. High rates of gain between 2 and 14 wk of age resulted in greater lumenal area and reduced cell proliferation in mammary parenchyma at 14 wk of age. Changes in FN deposition could have mediated growth differences.en
dc.publisherVirginia Techen
dc.relation.haspartTHESIS.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectestrogen receptoren
dc.subjectheifersen
dc.subjectmammaryen
dc.subjectextracellular matrixen
dc.subjectNutritionen
dc.titleEffects of varying energy intakes on mammary growth and development in prepubertal heifersen
dc.typeThesisen
dc.contributor.departmentDairy Scienceen
dc.description.degreeMaster of Scienceen
thesis.degree.nameMaster of Scienceen
thesis.degree.levelmastersen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.disciplineDairy Scienceen
dc.contributor.committeechairAkers, Robert Michaelen
dc.contributor.committeememberHoward, Rick Daleen
dc.contributor.committeememberPearson, Ronald E.en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-05192003-133446/en
dc.date.sdate2003-05-19en
dc.date.rdate2003-06-09en
dc.date.adate2003-06-09en


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