{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/31576"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/31576","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Environmental factors, pasture composition, growth rate and puberty in growing Thoroughbreds","abstract":"A 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.","abstract_html":"A 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&#x27;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&lt;0.0001), IGF-I (r = 0.25; P&lt;0.01) and ADG (r = 0.34; P&lt;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.","abstract_has_math":false,"creators":["Cubitt, Tania Anne"],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Animal and Poultry Sciences","degree_department":"Animal and Poultry Sciences","school":null,"contributors":[],"advisors":[],"committee_chairs":["Kronfeld, David S.","Splan, Rebecca K."],"committee_members":["Gwazdauskas, Francis C.","Herbein, Joseph H. Jr.","Staniar, William Burton"],"year":2004,"date_issued":"2004-01-05","date_published":"2004-01-05","updated_at":"2026-07-22T22:20:23Z","subjects":["Yearlings","Growth","Progesterone","Environment"],"languages":[],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-03302004-114931"],"render_values":[{"text":"etd-03302004-114931","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/31576","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Kronfeld, David S.","Splan, Rebecca K."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Gwazdauskas, Francis C.","Herbein, Joseph H. Jr.","Staniar, William Burton"]},{"key":"dc:contributor.department","label":"Department","values":["Animal and Poultry Sciences"]},{"key":"dc:creator","label":"Author","values":["Cubitt, Tania Anne"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-03-14T20:32:59Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-03-14T20:32:59Z","2012-11-20"]},{"key":"dc:date.issued","label":"Date","values":["2004-01-05"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Animal and Poultry Sciences"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Yearlings","Growth","Progesterone","Environment"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-03302004-114931"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10919/31576"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["A 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."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:title","label":"Title","values":["Environmental factors, pasture composition, growth rate and puberty in growing Thoroughbreds"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Kronfeld, David S.","Splan, Rebecca K."],"dc:contributor.committeemember":["Gwazdauskas, Francis C.","Herbein, Joseph H. Jr.","Staniar, William Burton"],"dc:contributor.department":["Animal and Poultry Sciences"],"dc:creator":["Cubitt, Tania Anne"],"dc:date.accessioned":["2014-03-14T20:32:59Z"],"dc:date.available":["2014-03-14T20:32:59Z","2012-11-20"],"dc:date.issued":["2004-01-05"],"dc:description.abstract":["A 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."],"dc:description.degree":["Master of Science"],"dc:identifier.other":["etd-03302004-114931"],"dc:identifier.uri":["http://hdl.handle.net/10919/31576"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["Yearlings","Growth","Progesterone","Environment"],"dc:title":["Environmental factors, pasture composition, growth rate and puberty in growing Thoroughbreds"],"dc:type":["Thesis"],"thesis:degree_discipline":["Animal and Poultry Sciences"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:20:23Z"}