Effect of dietary phosphorus level on performance and mineral status of grazing cattle in a warm climate region of central Florida

摘要

Athreeyearstudywasconductedtodeterminetheeffectofsupplementalphosphoruslevel(infreechoicemineralmixture)onperformanceandmineralstatusofgrazingcattleinaranchincentralFlorida.Thelowphosphorus(LP)grouphadalower(P0.05)pregnancyrateinyear1whentheconcentrationsofdietaryPwere4%(LP),8%mediumphosphorus(MP)and12%highphosphorus(HP).Pregnancyratesweresimilar(P0.05)inyears2and3whendietaryPlevelswere6%(LP),8%(MP)and12%(HP).TreatmenteffectonbodyweightwasobservedonlyinNovemberwithHPgrouphavingheavier(P0.01)weights.NovemberweightswerehigherthanMayweights(P0.01)inallgroups.Treatmenteffect(P0.05)oncowserummineralconcentrationsofCa,P,MgandCuinbothMayandNovemberwereobserved.CowserummineralsbelowthecriticalvaluewereobservedforMg,PandZn.Treatmenteffectsontissuemineralconcentrationswereminimal,suggestingthatanimalsweregenerallyreceivingadequatemineralsfromtheirdietscombinedwiththemineralsupplement.Meanlivermineralconcentrationsweresimilar(P0.05)inalltreatmentsandinallyears,exceptforPandMn.Allmineralelementswereabovethecriticalvalues,exceptMninMPgroupinyear2.Bonemineralconcentrations,percentashandspecificgravityweresimilar(P0.10)foralltreatmentsandyears.Phosphoruswasadequateinalltreatments.AshwaslowinLPgroupinallyearsandMPgroupofyear2.