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dc.contributor.authorCubitt, Tania Anneen_US
dc.date.accessioned2014-03-14T20:32:59Z
dc.date.available2014-03-14T20:32:59Z
dc.date.issued2004-01-05en_US
dc.identifier.otheretd-03302004-114931en_US
dc.identifier.urihttp://hdl.handle.net/10919/31576
dc.description.abstractA rapid growth phase often occurs with the onset of spring in the young horse. This coincides with changes in day length, temperature, and progesterone concentrations. The change in growth, from slow to rapid in young horses has been associated with various forms of developmental orthopedic disease. The objective of this study was to distinguish associations between progesterone concentrations and other physiological and environmental measures from birth through 16 mo in young Thoroughbreds. Growth data and plasma samples were collected monthly from 3 annual crops of 20 foals. Plasma progesterone (P4) and insulin like growth factor one (IGF-I) concentrations were measured with previously validated radio immunoassay's (RIA). Progesterone concentrations were compared with day length, IGF-I and ADG using Spearman correlations. Concentrations of progesterone at birth (2.3 ± 0.4 ng/mL) decreased within the first week of life to basal values (0.11 ± 0.01 ng/mL) in colts and fillies. Progesterone in the geldings remained at baseline concentrations at all sample times. An abrupt increase in progesterone concentration was detected in fillies at a mean age of 385 ± 6.4 d, weight 381 ± 7.2 kg, and ADG 0.63 ± 0.04 kg/d. Elevations in progesterone concentrations coincided with a measured day length of 13 ± 0.1 hrs, and temperature of 15 ± 1.7 °C. Positive associations were established between progesterone concentration day length (r = 0.59; P<0.0001), IGF-I (r = 0.25; P<0.01) and ADG (r = 0.34; P<0.0001). Day length IGF-I and ADG began to increase for both geldings and fillies at approximately 340 d of age, while progesterone started to increase at 385 ± 6.4 d for the fillies only. From this it could be hypothesized that an increase in ADG combined with optimal environmental conditions, may be associated with the subsequent elevation in progesterone concentrations in fillies. The relationship between IGF-I, and various reproductive hormones has been studied in the adult horse, yet the associations between environmental factors, ADG, and progesterone concentrations demonstrated in growing yearlings further emphasizes the extensive changes occurring during this crucial developmental stage.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartThesisFinal.pdfen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectYearlingsen_US
dc.subjectGrowthen_US
dc.subjectProgesteroneen_US
dc.subjectEnvironmenten_US
dc.titleEnvironmental factors, pasture composition, growth rate and puberty in growing Thoroughbredsen_US
dc.typeThesisen_US
dc.contributor.departmentAnimal and Poultry Sciencesen_US
dc.description.degreeMaster of Scienceen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.levelmastersen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineAnimal and Poultry Sciencesen_US
dc.contributor.committeechairKronfeld, David S.en_US
dc.contributor.committeememberGwazdauskas, Francis C.en_US
dc.contributor.committeememberHerbein, Joseph H. Jr.en_US
dc.contributor.committeememberStaniar, William Burtonen_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-03302004-114931/en_US
dc.contributor.committeecochairSplan, Rebecca K.en_US
dc.date.sdate2004-03-30en_US
dc.date.rdate2012-11-20
dc.date.adate2004-05-04en_US


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