选择免疫力较好的绵羊减少抗生素的使用.pdf

1、Agriculture and Natural ResourcesSelecting sheep with improved immunity to reduce antibiotic useScott Bowdridge,Ph.D.Professor and Livestock Extension SpecialistAgriculture and Natural ResourcesHaemonchuscontortusAgriculture and Natural ResourcesLessons learned in California40%increase in fecal egg

2、count(FEC)after Valbazen trmt-16%decrease in fecal egg count(FEC)after Cydectin trmtAgriculture and Natural ResourcesSomething more recentFor dewormer to be effective FECR 96%Oknow what?Agriculture and Natural ResourcesResistantImmune ResponseGINParasitismLarval EstablishmentAdultsFecundityHost Deat

3、hPasture InfectionAgriculture and Natural ResourcesResistantAgriculture and Natural ResourcesSusceptibleImmune ResponseLarval EstablishmentAdultsFecundityGINParasitismHost DeathPasture InfectionAgriculture and Natural ResourcesThe mechanism of parasite resistance in sheep is better immune responsesA

4、griculture and Natural Resources“A sheep will search its entire life to find a way to kill itself”Agriculture and Natural ResourcesDeath loss in Katahdin lambs under selection for parasite resistance051015202530201820192020202120222023Death Loss(%)Low-PFEC SiredHigh-PFEC SiredAgriculture and Natural

5、 ResourcesDeath loss in Katahdin lambs under selection for parasite resistance A 20%difference in death loss Both genotypes are exposed to“dirty”environment Survival despite high pathogen loadAgriculture and Natural ResourcesAgriculture and Natural ResourcesIgG response to CDT vaccination in Katahdi

6、n lambs by PFEC EBV typeLow+50Agriculture and Natural ResourcesWhat else if PFEC EBV linked to?Agriculture and Natural ResourcesLets revisit St.Croix SheepAgriculture and Natural ResourcesAgriculture and Natural ResourcesAgriculture and Natural ResourcesParasite Resistant Sheep A