Periconceptional Heat Stress of Holstein Cows Affects Subsequent Production Parameters Measured During Adulthood

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dc.contributor.authorBrown, Britni M.en
dc.contributor.committeechairRhoads, Michelleen
dc.contributor.committeememberJames, Robert E.en
dc.contributor.committeememberCassell, Bennet G.en
dc.contributor.committeememberKnight, James W.en
dc.contributor.departmentAnimal and Poultry Sciencesen
dc.date.accessioned2013-09-05T08:00:17Zen
dc.date.available2013-09-05T08:00:17Zen
dc.date.issued2013-09-04en
dc.description.abstractPericonceptional heat stress is known to reduce the likelihood of establishing pregnancy; however, some conceptuses will survive. Of the pregnancies that continue to term, a proportion will be heifers which are retained as replacement animals. Alterations that occur as a result of exposure to thermal stress during such critical stages in development likely result in differential performance between the heat stress-conceieved (HSC) cows and thermoneutral-conceived (TNC) cows. National Dairy Herd Improvement Association data was obtained from Dairy Records Management Systems. Records (n =14,189,891) included cows born between 1977 and 2010 in FL, GA, SC, MS, LA, AL, and TX. Records were edited to include only Holsteins born between 2000 and 2010 (n = 704,419). Conception dates were calculated by subtracting 276 d from the recorded birth date. Records for cows conceived within the months of June, July, and August were retained as HSC cows; cows conceived within the months of December, January, and February were retained as TNC contemporaries. Significant differences (P<0.01) in mature-equivalent milk yield were observed in all first lactation cows, and in cows that were retained within one herd for three lactations. In the latter group alterations in milk compositions were statistically significant (P<0.01), but not biologically so. Furthermore, significant differences (P<0.01) in days open were observed in cows retained within one herd for three lactations. The effects of periconceptional heat stress were particularly noticeable during seasonal comparisons, with HSC cows seemingly having an advantage in subsequent episodes of heat stress.en
dc.description.degreeMaster of Scienceen
dc.format.mediumETDen
dc.identifier.othervt_gsexam:1602en
dc.identifier.urihttp://hdl.handle.net/10919/23749en
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectdairy cowen
dc.subjectheat stressen
dc.subjectReproductionen
dc.subjectlactationen
dc.titlePericonceptional Heat Stress of Holstein Cows Affects Subsequent Production Parameters Measured During Adulthooden
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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