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 Testis T TE2E2 Surge Center Does not Develop Surge Center Does not Develop Blood Brain Barrier

5. Female Brain Development Ovary E2E2 E2E2 E2E2 Placenta E2E2 Blood Brain Barrier

6. Female Brain Development Ovary E2E2 E2E2 E2E2 Placenta E2E2  FP + E 2 Surge Center Develops Surge Center Develops Blood Brain Barrier

7. Fundamental Male and Female Differences Surge + Tonic Tonic Pulse Patterns

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) SpeciesMaleFemale Bovine11 mo (7-18)11 mo (9-24) Ovine7 mo (6-9)7 mo (4-14) Porcine7 mo (5-8)6 mo (5-7) Equine14 mo (10-24)18 mo (12-19) Human13 yr12 yr Canine9 mo (5 - 12)12 mo (6 - 24) Feline9 mo (8 - 10)8 mo (4 -12)

12. Puberty Hormonal Nutritional Genetic Environment

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 Tonic Surge 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 Positive Feedback is possible prior to puberty Puberty = 28 - 30 weeks

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 LH (ng/ml) FSH (ng/ml) Testosterone (ng/ml) LH FSH T T

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

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

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

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 3 2 1 01234567891011 Time (hours) LH (ng/ml) GnRH Before 2DGDuring 2DG

36. Effect of 2-deoxyglucose on LH Pulses Decreased Amplitude and Frequency 3 2 1 01234567891011 Time (hours) LH (ng/ml) GnRH Before 2DGDuring 2DG

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

38. Effect of Nutrition on Puberty 12 10 8 6 4 2 0 0 4812 162024 Body Weight (X 100 lbs.) Age (months) Puberty 2.0 lb/day 1.2 lb/day 1.5 lb/day

39. Dairy Cattle30-40% Beef cattle 55-65% Sheep40- 63% % Mature Weight at Puberty

40. Environmental and Social Conditions

41. Effect of the Number of Females Housed Together and Exposure to A Male

42. 28 Weeks 32 Weeks 24 Weeks

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

44. Puberty Hormonal Nutritional Genetic Environment

45. Recommended Age to Breed Heifer15 months (65% mature BW) Bull15 natural mating, 12 months AI Filly2-3 years Colt2 years Boar9 months