Animal Science 434PubertyPuberty in the FemalePuberty in the MaleAverage Age of Puberty (Range)Slide 6Role of GnRH PulsesGnRH Pulses Determine PubertyHormonal Changes in the MalePuberty in the StallionPowerPoint PresentationSlide 12Slide 13Hormonal Changes in the FemaleSlide 15Hypothalamus GnRH Control Centers in the FemaleMale Brain DevelopmentFemale Brain DevelopmentChanges in LH Secretion With PubertyPotential Regulators of GnRH Pulses at PubertyDevelopment of the Hypothalamic GnRH Surge CenterDevelopment of Estradiol Positive FeedbackSlide 23Slide 24Slide 25Silent Ovulation at PubertyGeneticsInfluence 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 36Influence of Growth Rate and Bull Exposure on Age of PubertySlide 38Recommended Age to BreedLecture Exam 1 Includes:Animal Science 434Lecture 8: The Onset of PubertyPubertyThe 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 (5-70equine 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 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)LHLHFSHFSHTTHormonal Changes in the FemaleHypothalamus GnRH Control Centers in the FemaleWhy does the maleonly have tonic control centers develop?Male Brain DevelopmentFemale Brain DevelopmentChanges in LH Secretion With PubertySurgeTonicSurgeTonicPotential Regulators of GnRH Pulses at Puberty•Development of surge center•Change in the feedback sensitivity to estradiolDevelopment of the Hypothalamic GnRH Surge CenterDevelopment of Estradiol Positive FeedbackAge (weeks) 18 22 26 30 34 38 42Development of Estradiol Positive FeedbackDevelopment of Estradiol Positive FeedbackNegative FeedbackPositive FeedbackPuberty in the FemaleSilent Ovulation at PubertyGeneticsInfluence 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 monthsLecture Exam 1 Includes:•lectures through tues (some points I have missed will be covered)•all handouts and lecture outlines•chapters 1-6 in text•exam format–multiple choice–true/false–short answer–one essay question on mechanism of hormone action (drawing a diagram will not be a suitable
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