Animal Science 434Development of Hypothalamus and GnRH Release CentersHypothalamus GnRH Control Centers in the FemaleMale Brain DevelopmentFemale Brain DevelopmentPowerPoint PresentationPubertyPuberty in the FemalePuberty in the MaleAverage Age of Puberty (Range)Slide 11Role of GnRH PulsesGnRH Pulses Determine PubertyHormonal Changes in the FemaleChanges in GnRH Secretion With PubertySlide 16Potential Regulators of GnRH Pulses at PubertyDevelopment of the Hypothalamic GnRH Surge CenterChanges in Feeback Sensitivity to EstradiolSlide 20Silent Ovulation at PubertyHormonal Changes in the MalePuberty in the StallionSlide 24Slide 25GeneticsInfluence of Breed on Age of PubertyNutritionAvailability of Energy Changes with GrowthEffect of 2-deoxyglucose on LH PulsesEffect of Nutrition on Puberty% Mature Weight at PubertyEnvironmental and Social ConditionsEffect of the Number of Females Housed Together and Exposure to A MaleSlide 35Influence of Growth Rate and Bull Exposure on Age of PubertySlide 37Recommended Age to BreedAnimal Science 434Lecture 8: The Onset of PubertyDevelopment of Hypothalamus and GnRH Release CentersHypothalamus GnRH Control Centers in the FemaleWhy does the maleonly have tonic control centers develop?Male Brain DevelopmentTestisTT E2Surge CenterDoes notDevelopSurge CenterDoes notDevelopBlood BrainBarrierFemale Brain DevelopmentOvaryE2E2E2PlacentaE2FP + E2Surge CenterDevelopsSurge CenterDevelopsBlood BrainBarrierPubertyThe ability to accomplish reproduction successfully.Puberty in the Female•Age at first estrus (heat)•Age at first ovulation•Age at which the female can support pregnancyPuberty in the Male•Age when behavioral traits are expressed•Age at first ejaculation•Age when sperm first appear in the ejaculate•Age when sperm first appear in the urine•Age when the ejaculate contains a threshold number of spermAverage Age of Puberty (Range)Species Male FemaleBovine 11 mo (7-18) 11 mo (9-24)Ovine 7 mo (6-9) 7 mo (4-14)Porcine 7 mo (5-8) 6 mo (5-7)Equine 14 mo (10-24) 18 mo (12-19)Human 13 yr 12 yrPubertyHormonalNutritionalGeneticEnvironmentRole of GnRH PulsesHormonalGnRH Pulses Determine Puberty•Prepubertal period»minimal GnRH release»FSH and LH low»minimal to no folliculargenesis or spermatogenesis•Puberty »increase in the pulse frequency and amplitude of GnRH release»increase in FSH and LH pulses»folliculargenesis and spermatogenesis occurHormonal Changes in the FemaleChanges in GnRH Secretion With PubertySurgeTonicSurgeTonicSurgeTonicPotential Regulators of GnRH Pulses at Puberty•Development of surge center•Change in the feedback sensitivity to estradiolDevelopment of the Hypothalamic GnRH Surge CenterPositive Feedback is possible prior to pubertyPuberty = 28 - 30 weeksPuberty = 28 - 30 weeksNegative Feedback Decreased Neg. FeedbackChanges in Feeback Sensitivity to EstradiolPuberty in the FemaleSilent Ovulation at PubertyHormonal Changes in the MalePuberty in the Stallion0510152025FSH (ng/ml)0 20 40 60 80 10000.511.5Testosterone (ng/ml)0 20 40 60 80 10002468LH (ng/ml)0 20 40 60 80 100Age (wk)PubertyLH (ng/ml)LH (ng/ml)FSH (ng/ml)FSH (ng/ml)Testosterone (ng/ml)LHLHFSHFSHTT0510152025FSH (ng/ml)0 20 40 60 80 10000.511.5Testosterone (ng/ml)0 20 40 60 80 10002468LH (ng/ml)0 20 40 60 80 100Age (wk)Increased GonadotropinsTestosterone Remains LowCaused by GnRH•Sertoli cells mature and multiply•Spermatogonia begin to divideLH (ng/ml)LH (ng/ml)FSH (ng/ml)FSH (ng/ml)Testosterone (ng/ml)LHLHFSHFSHTT0510152025FSH (ng/ml)0 20 40 60 80 10000.511.5Testosterone (ng/ml)0 20 40 60 80 10002468LH (ng/ml)0 20 40 60 80 100Age (wk)PubertyTestosterone IncreasesSperm found in the ejaculateFSH IncreasesLH (ng/ml)LH (ng/ml)FSH (ng/ml)FSH (ng/ml)Testosterone (ng/ml)LHLHFSHFSHTTGeneticsInfluence of Breed on Age of Puberty Species Female Male Cattle Holstein 8.5 9.0Brown Swiss 11.6 8.8Angus 12.4 9.8Hereford 13.0 10.8Brahman 19.0 17.0 Swine Meishan 3.1 3.0Large White 6.3 5.8Yorkshire 7.0 6.5 Sheep Rambouillet 9.2Finish Landrace 8.6Average Age at Puberty (Months)NutritionAvailability of Energy Changes with GrowthEffect of 2-deoxyglucose on LH PulsesDecreased Amplitude andFrequencyEffect of Nutrition on PubertyDairy Cattle 30-40%Beef cattle 55-65%Sheep 40- 63%% Mature Weight at PubertyEnvironmental and Social ConditionsEffect of the Number of Females Housed TogetherandExposure to A Male28 Weeks32Weeks24 Weeks24 WeeksInfluence of Growth Rate and Bull Exposure on Age of PubertyHigh Growth RateModerate Growth RateHigh Growth RateModerate Growth Rate0100200300400500Age at Puberty (days)HeifersonlyBullExposure449428422375PubertyHormonalNutritionalGeneticEnvironmentRecommended Age to Breed•Heifer 15 months (65% mature BW)•Bull 15 natural mating, 12 months AI•Filly 2-3 years•Colt 2 years•Boar 9
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