{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/39247"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/39247","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Reproductive performance of dorset ewes in the star accelerated lambing system","abstract":"Reproductive performance of Dorset ewes in the Cornell University STAR accelerated lambing program was evaluated. This program consists of five 30-d concurrent breeding and lambing periods per year beginning on January 1 (Sl), March 15 (S2), May 27 (S3), August 8 (S4) and October 20 (S5). Optimally, a ewe could lamb every 7.2 mo beginning at 1 yr of age, Records on 1,084 ewes over 7 yr beginning S1, 1982 Reproductive traits considered were ewe fertility, prolificacy, days to first lambing (DFL) and days between lambing (DBL). Fertility and prolificacy differed (P < .001) by exposure seasons. Exposure during favorable seasons (S1, S4, S5) increased fertility (P < .001) and prolificacy (P < .01) over that observed in unfavorable seasons (S2, S3). On average, first lambing occurred at 476 ± 5 d with ewe lambs first exposed during S1, S4 and S5 lambing at younger ages (P < .001). Ewes had more DBL (P < .001) if initial exposure following lambing occurred during an unfavorable season. A curvilinear relationship of ewe age with fertility (P < .001) , prolificacy (P < .01) and DBL (P < .05) was observed in ewes less than 4 yr old. At first exposure following lambing, fertility was lower (P < .001) than at subsequent exposures and ewes that had nursed lambs were less prolific (P < .01) than those that had not. Prolificacy and nursing status had little effect on fertility or DBL (P > .10). Fertility was transformed to an underlying liability scale based on the expected fertility of ewes of a given age and reproductive history. Variance components were estimated by least-squares (LS) and restricted maximum likelihood (REML) procedures. First-exposure fertility was not heritable. heritabilities for fertility at first post-lambing exposure, first-lambing prolificacy, and second-lambing prolificacy were .191 ± .088 (LS) and .200 ± .132 (REML), .914 ± .091 (LS) and .158 ± .144 (REML), and .168 ± .082 (LS) and .210 ± .137 (REML), respectively. Genetic variation in DFL (P < .01) and DBL (P < .001) was found. Although intrasire ewe variation was detected for prolificacy (P < .001) and DBL (P < .01), repeatability estimates were low and smaller than heritability.","abstract_html":"Reproductive performance of Dorset ewes in the Cornell University STAR accelerated lambing program was evaluated. This program consists of five 30-d concurrent breeding and lambing periods per year beginning on January 1 (Sl), March 15 (S2), May 27 (S3), August 8 (S4) and October 20 (S5). Optimally, a ewe could lamb every 7.2 mo beginning at 1 yr of age, Records on 1,084 ewes over 7 yr beginning S1, 1982 Reproductive traits considered were ewe fertility, prolificacy, days to first lambing (DFL) and days between lambing (DBL). Fertility and prolificacy differed (P &lt; .001) by exposure seasons. Exposure during favorable seasons (S1, S4, S5) increased fertility (P &lt; .001) and prolificacy (P &lt; .01) over that observed in unfavorable seasons (S2, S3). On average, first lambing occurred at 476 ± 5 d with ewe lambs first exposed during S1, S4 and S5 lambing at younger ages (P &lt; .001). Ewes had more DBL (P &lt; .001) if initial exposure following lambing occurred during an unfavorable season. A curvilinear relationship of ewe age with fertility (P &lt; .001) , prolificacy (P &lt; .01) and DBL (P &lt; .05) was observed in ewes less than 4 yr old. At first exposure following lambing, fertility was lower (P &lt; .001) than at subsequent exposures and ewes that had nursed lambs were less prolific (P &lt; .01) than those that had not. Prolificacy and nursing status had little effect on fertility or DBL (P &gt; .10). Fertility was transformed to an underlying liability scale based on the expected fertility of ewes of a given age and reproductive history. Variance components were estimated by least-squares (LS) and restricted maximum likelihood (REML) procedures. First-exposure fertility was not heritable. heritabilities for fertility at first post-lambing exposure, first-lambing prolificacy, and second-lambing prolificacy were .191 ± .088 (LS) and .200 ± .132 (REML), .914 ± .091 (LS) and .158 ± .144 (REML), and .168 ± .082 (LS) and .210 ± .137 (REML), respectively. Genetic variation in DFL (P &lt; .01) and DBL (P &lt; .001) was found. Although intrasire ewe variation was detected for prolificacy (P &lt; .001) and DBL (P &lt; .01), repeatability estimates were low and smaller than heritability.","abstract_has_math":false,"creators":["Lewis, Ronald M."],"institution":"Virginia Tech","degree_name":"Ph. 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This program consists of five 30-d concurrent breeding and lambing periods per year beginning on January 1 (Sl), March 15 (S2), May 27 (S3), August 8 (S4) and October 20 (S5). Optimally, a ewe could lamb every 7.2 mo beginning at 1 yr of age, Records on 1,084 ewes over 7 yr beginning S1, 1982 Reproductive traits considered were ewe fertility, prolificacy, days to first lambing (DFL) and days between lambing (DBL). Fertility and prolificacy differed (P < .001) by exposure seasons. Exposure during favorable seasons (S1, S4, S5) increased fertility (P < .001) and prolificacy (P < .01) over that observed in unfavorable seasons (S2, S3). On average, first lambing occurred at 476 ± 5 d with ewe lambs first exposed during S1, S4 and S5 lambing at younger ages (P < .001). Ewes had more DBL (P < .001) if initial exposure following lambing occurred during an unfavorable season. A curvilinear relationship of ewe age with fertility (P < .001) , prolificacy (P < .01) and DBL (P < .05) was observed in ewes less than 4 yr old. At first exposure following lambing, fertility was lower (P < .001) than at subsequent exposures and ewes that had nursed lambs were less prolific (P < .01) than those that had not. Prolificacy and nursing status had little effect on fertility or DBL (P > .10). Fertility was transformed to an underlying liability scale based on the expected fertility of ewes of a given age and reproductive history. Variance components were estimated by least-squares (LS) and restricted maximum likelihood (REML) procedures. First-exposure fertility was not heritable. heritabilities for fertility at first post-lambing exposure, first-lambing prolificacy, and second-lambing prolificacy were .191 ± .088 (LS) and .200 ± .132 (REML), .914 ± .091 (LS) and .158 ± .144 (REML), and .168 ± .082 (LS) and .210 ± .137 (REML), respectively. Genetic variation in DFL (P < .01) and DBL (P < .001) was found. Although intrasire ewe variation was detected for prolificacy (P < .001) and DBL (P < .01), repeatability estimates were low and smaller than heritability."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph. D."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["BTD"]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Reproductive performance of dorset ewes in the star accelerated lambing system"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Notter, David R."],"dc:contributor.committeemember":["Pearson, Ronald","Umberger, Steven H.","Vinson, William E.","Hinkelmann, Klaus","Hoeschele, Ina","Hohenboken, William D."],"dc:contributor.department":["Animal Science"],"dc:creator":["Lewis, Ronald M."],"dc:date.accessioned":["2014-03-14T21:18:15Z"],"dc:date.available":["2014-03-14T21:18:15Z","2008-08-25"],"dc:date.issued":["1990-05-05"],"dc:description.abstract":["Reproductive performance of Dorset ewes in the Cornell University STAR accelerated lambing program was evaluated. This program consists of five 30-d concurrent breeding and lambing periods per year beginning on January 1 (Sl), March 15 (S2), May 27 (S3), August 8 (S4) and October 20 (S5). Optimally, a ewe could lamb every 7.2 mo beginning at 1 yr of age, Records on 1,084 ewes over 7 yr beginning S1, 1982 Reproductive traits considered were ewe fertility, prolificacy, days to first lambing (DFL) and days between lambing (DBL). Fertility and prolificacy differed (P < .001) by exposure seasons. Exposure during favorable seasons (S1, S4, S5) increased fertility (P < .001) and prolificacy (P < .01) over that observed in unfavorable seasons (S2, S3). On average, first lambing occurred at 476 ± 5 d with ewe lambs first exposed during S1, S4 and S5 lambing at younger ages (P < .001). Ewes had more DBL (P < .001) if initial exposure following lambing occurred during an unfavorable season. A curvilinear relationship of ewe age with fertility (P < .001) , prolificacy (P < .01) and DBL (P < .05) was observed in ewes less than 4 yr old. At first exposure following lambing, fertility was lower (P < .001) than at subsequent exposures and ewes that had nursed lambs were less prolific (P < .01) than those that had not. Prolificacy and nursing status had little effect on fertility or DBL (P > .10). Fertility was transformed to an underlying liability scale based on the expected fertility of ewes of a given age and reproductive history. Variance components were estimated by least-squares (LS) and restricted maximum likelihood (REML) procedures. First-exposure fertility was not heritable. heritabilities for fertility at first post-lambing exposure, first-lambing prolificacy, and second-lambing prolificacy were .191 ± .088 (LS) and .200 ± .132 (REML), .914 ± .091 (LS) and .158 ± .144 (REML), and .168 ± .082 (LS) and .210 ± .137 (REML), respectively. Genetic variation in DFL (P < .01) and DBL (P < .001) was found. Although intrasire ewe variation was detected for prolificacy (P < .001) and DBL (P < .01), repeatability estimates were low and smaller than heritability."],"dc:description.degree":["Ph. D."],"dc:format.medium":["BTD"],"dc:format.mimetype":["application/pdf"],"dc:identifier.other":["etd-08252008-162636"],"dc:identifier.uri":["http://hdl.handle.net/10919/39247"],"dc:language.iso":["en"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:title":["Reproductive performance of dorset ewes in the star accelerated lambing system"],"dc:type":["Dissertation"],"dc:type.dcmitype":["Text"],"thesis:degree_discipline":["Animal Science"],"thesis:degree_level":["doctoral"],"thesis:degree_name":["Ph. D."],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:18:53Z"}