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Animal Science 434

Animal Science 434. Lecture 8: The Onset of Puberty. Development of Hypothalamus and GnRH Release Centers. Males and Females are Different!!!. Hypothalamus GnRH Control Centers in the Female. Why does the male only have tonic control centers develop?. Male Brain Development. T. Testis.

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Animal Science 434

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  1. Animal Science 434 Lecture 8: The Onset of Puberty

  2. Development of Hypothalamus and GnRH Release Centers Males and Females are Different!!!

  3. Hypothalamus GnRH Control Centers in the Female Why does the male only have tonic control centers develop?

  4. Male Brain Development T Testis T E2 Surge Center Does not Develop Blood Brain Barrier

  5. Female Brain Development Placenta E2 E2 E2 E2 Ovary Blood Brain Barrier

  6. Female Brain Development aFP + E2 Placenta E2 E2 E2 E2 Ovary Surge Center Develops Blood Brain Barrier

  7. Fundamental Male and Female Differences PulsePatterns Surge + Tonic Tonic

  8. Puberty The ability to accomplish reproduction successfully.

  9. Puberty in the Female • Age at first estrus (heat) • Age at first ovulation • Age at which the female can support pregnancy

  10. Puberty 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 sperm

  11. Average Age of Puberty (Range) Species Male Female Bovine 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 yr Canine 9 mo (5 - 12) 12 mo (6 - 24) Feline 9 mo (8 - 10) 8 mo (4 -12)

  12. Puberty Genetic Hormonal Environment Nutritional

  13. Role of GnRH Pulses Hormonal

  14. GnRH 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 occur

  15. Hormonal Changes in the Female

  16. Changes in GnRH Secretion With Puberty Surge Tonic Low Amplitude and Frequency

  17. Changes in GnRH Secretion With Puberty Surge Tonic

  18. Changes in GnRH Secretion With Puberty Surge Surge Tonic Tonic

  19. Surge Tonic

  20. Potential Regulators of GnRH Pulses at Puberty • Development of surge center • Change in the feedback sensitivity to estradiol

  21. Development of the Hypothalamic GnRH Surge Center Puberty = 28 - 30 weeks

  22. Development of the Hypothalamic GnRH Surge Center Puberty = 28 - 30 weeks Positive Feedback is possible prior to puberty

  23. Negative Feedback Decreased Neg. Feedback Changes in Feeback Sensitivity to Estradiol

  24. Puberty in the Female

  25. Silent Ovulation at Puberty

  26. Hormonal Changes in the Male

  27. Puberty in the Stallion Puberty FSH LH (ng/ml) FSH (ng/ml) Testosterone (ng/ml) LH T

  28. Caused by GnRH Increased Gonadotropins FSH LH (ng/ml) FSH (ng/ml) Testosterone (ng/ml) LH T

  29. Sertoli cells mature and multiply • Spermatogonia begin to divide Testosterone Remains Low FSH LH (ng/ml) FSH (ng/ml) Testosterone (ng/ml) LH T

  30. FSH Increases Puberty FSH LH (ng/ml) FSH (ng/ml) Testosterone (ng/ml) LH T Sperm found in the ejaculate Testosterone Increases

  31. Genetics

  32. Influence of Breed on Age of Puberty Average Age at Puberty (Months)

  33. Nutrition

  34. Availability of Energy Changes with Growth

  35. Effect of 2-deoxyglucose on LH Pulses GnRH Before 2DG During 2DG 3 2 LH (ng/ml) 1 0 1 2 3 4 5 6 7 8 9 10 11 Time (hours)

  36. Effect of 2-deoxyglucose on LH Pulses GnRH Before 2DG During 2DG 3 2 LH (ng/ml) 1 0 1 2 3 4 5 6 7 8 9 10 11 Time (hours) Decreased Amplitude and Frequency

  37. Metabolic Signals Influence GnRH Neurons Blood Glucose Glucose sensingneurons ? Neuropeptide Y neurons GnRH neurons GnRH Leptin Fatty Acid sensing neurons ? Adipocytes (Fat) Blood Fatty Acids

  38. Effect of Nutrition on Puberty 12 1.5 lb/day 2.0 lb/day 10 8 1.2 lb/day Body Weight (X 100 lbs.) 6 Puberty 4 2 0 4 8 12 0 16 20 24 Age (months)

  39. % Mature Weight at Puberty Dairy Cattle 30-40% Beef cattle 55-65% Sheep 40- 63%

  40. Environmental and Social Conditions

  41. Effect of the Number of Females Housed TogetherandExposure to A Male

  42. 32 Weeks 28 Weeks 24 Weeks 24 Weeks

  43. Influence of Growth Rate and Bull Exposure on Age of Puberty Moderate Growth Rate High Growth Rate 500 449 428 422 400 375 300 Age at Puberty (days) 200 100 0 Heifers only Bull Exposure

  44. Puberty Genetic Hormonal Environment Nutritional

  45. Recommended 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 months

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