AVS 101 1st Edition Lecture 11Breeding, Pregnancy & GestationMating occurs during optimum fertilityProestrus Time prior to estrus (heat) Attracts mate Male arousalEstrus Lasts a few hours to a couple of daysPregnancy Fertilized egg migrates to uterus 16 cell stage of embryo Attaches to uterine wall via enzyme actionHorse embryo floats for weeks Delayed implantationPregnancy Uterus changes during cycleBuildup/tear down of uterine tissueProgesterone Produced by CL Maintains pregnancyIf CL removed from ovary à abortion Animals with long gestationCL drops in progesteronePlacenta produces progesteroneProlactin Maintains CL à progesterone à pregnancy maintained Initiates/maintains lactationIf pregnancy does not occur… CL regresses à CA No progesterone Cycle repeatsPregnancy Fertilization occurs in the upper third of the oviduct (fallopian tube)Placenta Development Umbilical cordAttached embryo to fetal membrane AllantoisAttach to fetal kidneyRemoves some waste AmnionWater bagProtects embryo ChorionGas & nutrient exchange02& nutrients into fetusC02 out to momNo direct exchange of bloodUterine Attachment DiffuseMost animals: pigs, dogs, cats, people, horse CotyledonousRuminants: sheep, cowsButton-like carunclesDystocia Difficulty birthing Causes: heavy birthweight, age of dam, pelvic area of damGestation – fertilization to birthBirth = ParturitionWhy it begins?? Placenta ages Decrease progesteroneCL gets old Increase ACTHPituitary hormone - adrenocorticotropic Increase in estrogen – “primes the uterus” Cervix must dilate OxytocinMade in brain, stored in pituitaryCauses uterine contractions RelaxinProduced in ovaryRelaxes pelvic
View Full Document
Unlocking...