Lactation specific and life time demographic parameters in a Holstein Friesian herd in the central highlands of Ethiopia

摘要

Thestudywasmadetoestimatethelactationspecificandlifetimedemographicparametersfromtherecordsof901HolsteinFriesiancowsbornintheperiodof1985to2008atHoletaBullDamStation,Ethiopia.Theprobabilityofacowbeinglostfromherdwas0.263duringthefirstlactationandtherateincreasedwithlactation.Survivalrateintheherdduringfirstlactationwasestimatedat0.738andtherateincreasedduringfirstthreelactationsandthereafterdeclinedataninconsistentrate.Stayabilityinthefarmwasmaximum(0.737)forcowsinfirstlactation,andcontinuouslydecreasedwithlactationnumber.Cowshadexpectedherdlifeof2.457lactationsatthefirstlactationandthereaftertheestimatecontinuedtodecline.Theprobabilityofproducingalivefemalecalfbyacowatherfirstlactationwas0.481andapproachedtheexpectedsexratioof50:50atthe4thand5thlactations.Thereproductivevalueofcowswasmaximumatthefirstlactationandallotherlactationshadlessthanone.Oldercowshadlowerreproductivevalue.Themeanlactationsofcowspresentandlostfromtheherdwereinaverage3.49and4.35lactations,respectivelyindicatingthatcowspresentinthefarmwereyounger.Theprobabilityofacowbeinglostfromtheherdandlifeexpectancyatbirthwasas0.32and1.28lactations,respectively.Thenetreproductiveratefortheherdwas1.50indicatingthateachcowproducedonanaverage1.5femalecalves.nbsp;Improvementinmostlactationspecificandpopulationparameterscanbeobtainedbyreducingforcedcullingandmortalityatearlyagethroughbetternutritionandreproductivehealthmanagement.nbsp;