EffectsofheatstressonenergeticmetabolisminlactatingHolsteincowsZhouLuoxiong11/03/2011AuthorsJ.B.Wheelock,R.P.Rhoads,M.J.VanBaaleS.R.Sanders,andL.H.BaumgardJournalofDairyScienceVol.93No.2,2010OutlineIntroductionExperimentalDesignResultsandDiscussionConlusionsIntroductionReducedfeedintakehastraditionallybeenassumedtobeprimarilyresponsibleforthedecreaseinmilkyieldPlasmaNEFAlevelsofheat-stressedcowsisdifferentsfrompoorfedcowsRecombinantbST(rbST)isawell-documentedgalactopoietictoolExperimentaldesignGroup1(n=12)Group2(n=10)P1Thermoneutralcondtions20℃adlibitumfeedintake(TN)Thermoneutralcondtions20℃adlibitumfeedintake(TN)P2Thermoneutralcondtions20℃Limit-fed(PF)Heat-stressedconditions29.4~38.9℃adlibitumfeedintake(HS)P3PF+rbST(PF)HS+rbST(HS)ResultsandDiscussionTheeffectsofheatstress(HS)orpair-feeding(PF)andrbSTon(A)DMIand(B)milkyieldinlactatingcowsTheeffectsofheatstress(HS)orpair-feeding(PF)andrbSTon(A)basalplasmaglucose,(B)NEFA,and(C)plasmaureanitrogen(PUN)inlactatingcowsTheeffectsofheatstress(HS)orpair-feeding(PF)andrecombinantbSTonplasmaglucoseandinsulinresponsetoaGTTinlactatingcows

ConclusionsReducednutrientintakeaccountedforonly50%ofheatstress-induceddecreasesinmilkyield,postabsorptivemetabolismchangesmayberesponsibleforalargeportionoftheremainderHeats-tressedcowshaveincreasedbasalandstimulatedinsulinlevels,resultingindecreasedadiposetissuelipidmobilizatio