1 / 40

Animal Science 434

Animal Science 434. Lecture 8: The Onset of Puberty. Puberty. The 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 pregnancy. Puberty in the Male.

zoie
Download Presentation

Animal Science 434

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  2. Puberty The ability to accomplish reproduction successfully.

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

  4. 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

  5. Average Age of Puberty (Range)

  6. Puberty Genetic Hormonal Environment Nutritional

  7. Role of GnRH Pulses Hormonal

  8. 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

  9. Hormonal Changes in the Male

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

  11. Caused by GnRH Increased Gonadotropins • Sertoli cells mature and multiply • Spermatogonia begin to divide Testosterone Remains Low FSH LH (ng/ml) FSH (ng/ml) Testosterone (ng/ml) LH T

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

  13. Hormonal Changes in the Female

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

  15. Male Brain Development

  16. Female Brain Development

  17. Changes in LH Secretion With Puberty Surge Surge Tonic Tonic

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

  19. Development of the Hypothalamic GnRH Surge Center

  20. Development of Estradiol Positive Feedback 18 22 26 30 34 38 42 Age (weeks)

  21. Development of Estradiol Positive Feedback

  22. Development of Estradiol Positive Feedback Negative Feedback Positive Feedback

  23. Puberty in the Female

  24. Silent Ovulation at Puberty

  25. Genetics

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

  27. Nutrition

  28. Availability of Energy Changes with Growth

  29. Effect of 2-deoxyglucose on LH Pulses Decreased Amplitude and Frequency

  30. Effect of Nutrition on Puberty

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

  32. Environmental and Social Conditions

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

  34. 32 Weeks 28 Weeks 24 Weeks 24 Weeks

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

  36. Puberty Genetic Hormonal Environment Nutritional

  37. 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

  38. Lecture 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 answer)

More Related