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Environmental factors, pasture composition, growth rate and puberty in growing Thoroughbreds

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dc.contributor.authorCubitt, Tania Anneen
dc.contributor.committeechairKronfeld, David S.en
dc.contributor.committeecochairSplan, Rebecca K.en
dc.contributor.committeememberGwazdauskas, Francis C.en
dc.contributor.committeememberHerbein, Joseph H. Jr.en
dc.contributor.committeememberStaniar, William Burtonen
dc.contributor.departmentAnimal and Poultry Sciencesen
dc.date.accessioned2014-03-14T20:32:59Zen
dc.date.adate2004-05-04en
dc.date.available2014-03-14T20:32:59Zen
dc.date.issued2004-01-05en
dc.date.rdate2012-11-20en
dc.date.sdate2004-03-30en
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
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-03302004-114931en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-03302004-114931/en
dc.identifier.urihttp://hdl.handle.net/10919/31576en
dc.publisherVirginia Techen
dc.relation.haspartThesisFinal.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectYearlingsen
dc.subjectGrowthen
dc.subjectProgesteroneen
dc.subjectEnvironmenten
dc.titleEnvironmental factors, pasture composition, growth rate and puberty in growing Thoroughbredsen
dc.typeThesisen
thesis.degree.disciplineAnimal and Poultry Sciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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