Reproductive behaviour of commercial Zebu cows with calves under a regime of restricted suckling

摘要

Atotalof153commercialZebucowswithameanliveweightof370kgwereallocatedatrandomtotwogroups:(a)cowspregnantand/orwithcalves;and(b)non-pregnantcowswithoutcalves.Thegrazingareawasmadeupof50haofAfricanStargrass(Cynodonplectostachyus),dividedin20paddocks,managedinrotationandfertilisedwith200kgofN/ha/yr.Alltheanimalsreceived3.5kg/dayofamolasses/urea(2.5%urea)supplement.Confirmationofanimalsinheat,inseminationsanddiagnosisofpregnancyweremadeusingconventionalprocedures.Thecalvesweremanagedunderasystemofrestrictedsucklingtwiceadayduringperiodsof30minutes.Theexperimenthadadurationof100days,betweenthemonthsofJuneandSeptember.Thepercentageofanimalscomingintoheatandconceivingwere82.5vs.86.0%,and55.5vs.65.9%forcowswithandwithoutcalves,respectively.Theintervalfromthebeginningofthematingseasontofirstheatwas46.9daysforcowswithcalves,and17.4daysforcowswithoutcalves(P0.001).Thevaluesfortheintervalbetweencalvingandfirstheat,andcalvingandconceptionwere79.7and90.9daysinthatorder.Thepercentageofcowsneedingmorethantwoservicestoachievepregnancywaslessinthetreatmentwithcowsthathadcalves(28.5%)thanthosewithout(43.1%).Theresponseinreproductionbehaviourobtainedfromtheanimalswithcalvesisdiscussedinrelationtothemolasses/ureasupplement.