The Acute and Chronic Effects of a Cyclic Heat Stress on 24 to 28 Week Old Laying Hens on Performance, Egg Quality, Apparent Metabolizable Energy, and Blood Chemistry

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dc.contributor.authorBarrett, Nathaniel W.en
dc.contributor.committeechairPersia, Michael E.en
dc.contributor.committeememberSchmidt, Carl J.en
dc.contributor.committeememberDalloul, Rami A.en
dc.contributor.departmentAnimal and Poultry Sciencesen
dc.date.accessioned2016-11-03T08:00:27Zen
dc.date.available2016-11-03T08:00:27Zen
dc.date.issued2016-11-02en
dc.description.abstractCommercial laying hens are heavily selected for increased egg production, but little selection has occurred for resistance to extreme temperatures. The objective of the experiment was to determine the effects of a daily cyclic heat stress (HS) on performance, body temperature, egg quality, nitrogen corrected apparent metabolizable energy, and blood chemistry in laying hens at acute and chronic time points. In total, 407 pure line laying hen pullets (18 wk) were sourced from Hy-Line International and housed individually for the duration of the experiment. Feed intake, egg production, and body weights were significantly decreased while egg weight and feed efficiency increased due to HS exposure. All egg quality parameters except yolk weight were decreased by HS exposure, including Haugh unit, eggshell and albumen weights. Egg yolk weights were increased over the first 2 wk of HS before falling. Blood chemistry was affected by HS resulting in respiratory alkalosis likely caused by increased respiration and evaporative cooling. There was a decrease in the PCO2, an increase in pH and a reduction in iCa in the blood within 4 to 6 hours of HS when compared to pre-HS levels. The data indicate that the hens were negatively affected by HS and the response was different for acute and chronic time points. At the acute time point the changes to the hen's physiology were caused by altered blood chemistry, but after chronic exposure, the low feed intake seemed to influence the responses.en
dc.description.degreeMaster of Scienceen
dc.format.mediumETDen
dc.identifier.othervt_gsexam:8986en
dc.identifier.urihttp://hdl.handle.net/10919/73369en
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectHeat stressen
dc.subjectlaying henen
dc.subjectPerformanceen
dc.subjectblood chemistryen
dc.subjectegg qualityen
dc.titleThe Acute and Chronic Effects of a Cyclic Heat Stress on 24 to 28 Week Old Laying Hens on Performance, Egg Quality, Apparent Metabolizable Energy, and Blood Chemistryen
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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