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Review of Reproductive Physiology

Ontario Association of Bovine Practitioners Reproductive Symposium. Department of Animal Sciences and Industry. Review of Reproductive Physiology. Jeffrey S. Stevenson, Ph.D. State of Kansas. #1 in wheat #1 cattle slaughtered #1 in sorghum grain (milo) #1 in sorghum silage produced

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Review of Reproductive Physiology

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  1. Ontario Association of Bovine Practitioners Reproductive Symposium Department of Animal Sciences and Industry Review of Reproductive Physiology Jeffrey S. Stevenson, Ph.D.

  2. State of Kansas #1 in wheat #1 cattle slaughtered #1 in sorghum grain (milo) #1 in sorghum silage produced #2 in acres of crop land #2 cattle and calves #5 in agricultural exports #10 in milk yield per dairy cow #18 in milk produced Manhattan 24-28 inches (640-711 mm) >40 inches (>1016 mm) 20 inches (508 mm) 32-36 inches (813-914 mm) 20-24 inches (508-640 mm) 28-32 inches (711-813 mm) 36-40 inches (914-1016 mm) Annual Precipitation

  3. Hypothalamus Gonadotropin-Releasing Hormone (GnRH) • Secreted by the GnRH-secreting neurons of the anterior and medial basal hypothalamus • Stimulates release of LH • Stimulates release of FSH • Induces ovulation through LH release • Marketed as gonadorelins: Cystorelin, Factrel, Fertagyl, and OvaCyst or as GnRH agonist: Buserelin or Receptal

  4. Hypothalamus Follicle-Stimulating Hormone (FSH) • Secreted by the anterior pituitary gland • Initiates cyclic waves of follicle growth • Recruits pre-antral follicles to develop an antrum and become antral follicles • Stimulates biosynthesis of estrogen by granulosa cells from thecal cell derived androgen precursors

  5. Hypothalamus Luteinizing Hormone (LH) • Secreted by the anterior pituitary gland • Stimulates antral follicle maturation • Induces ovulation of mature antral or pre-ovulatory follicles • Stimulates secretion of androgens by theca cells from cholesterol • Stimulates secretion of progesterone by the corpus luteum

  6. Theca cell Granulosa cell LH Cholesterol Cholesterol (+) (+) Pregnenolone Pregnenolone (–) (–) Testosterone Progesterone Progesterone (+) Androstenedione LH Estradiol-17 FSH Estradiol-17 Estradiol-17 (blood) (follicular fluid) Follicle basement membrane

  7. Ovary Estrogen (Estradiol-17) • Secreted by the follicle • Induces sexual behavior • Induces pre-ovulatory surge of LH • Stimulates development of reproductive tract • Synergizes with progesterone to induced proliferation and function of uterine glands and their secretions

  8. Ovary Progesterone CL Ovary • Secreted by the corpus luteum • Induces development of uterine endometrium • Prevents estrus and ovulation by negative feedback inhibition of LH secretion X X X

  9. Estrus 27 hr E2 P4 Onset of ovulation Onset of estrus LH E2 E2 E2 LH LH LH 0 2 4 0 2 4 0 2 4 Hours Hours Hours

  10. X CL Ovary Prostaglandin F2 • Secreted by the uterus • Induces death (lysis) of the corpus luteum (CL) • Initiates early uterine contractions as a smooth muscle stimulator • Marketed as Lutalyse, Prostamate, In-Synch, EstroPlan, and Estrumate (agonist)

  11. Ovulation Ovulation Proestrus Metestrus Diestrus Estrus Estrus E2 P4 LH LH PGF2 FSH 21 0 5 10 15 Days of the Bovine Estrous Cycle

  12. The Estrous Cycle: Follicle Waves, Progesterone, and Luteolysis

  13. Normal Interval to Estrus PGF2 Estrus

  14. Shorter Interval to Estrus after PGF Est rus PGF2

  15. Longer Interval to Estrus after PGF PGF2 Estrus

  16. GnRH-Induced Ovulation of Dominant Follicles LH dependent X X Estrus X X

  17. Growth and Development of Dominant Follicles (Suckled Cow) * * Follicle diameter (mm) * * Days postpartum Stagg et al. (1995)

  18. Early Postpartum Follicular Waves(Milked Cow) Ovulation Beam and Butler, 1996

  19. Frequency of LH Pulses

  20. No. of LH Pulses/8 hr - Milked Cows First ovulation followed the last blood collection series by 2.5  0.4 days. Canfield and Butler, 1990

  21. Energy Balance (+) (–) Metabolism and Partitioning Intake Expenditures Liver Reproduction Thermoregulation Oxidizable metabolic fuels Feed NEM Cell maintenance Locomotion Growth (NEG) Adipose tissue Fat stores Milk yield (NEL)

  22. Energy Balance and First Ovulation *Sufficient energy to produce 57 lb (26 kg) of milk/day Zurek et al. (1995)

  23. Uterine Involution Marion and Gier, 1968

  24. Nadir of EB IGF-I Ovulation E2 FSH LH Days postpartum Calving

  25. Body Condition Scores of Dairy Cattle at 70 DIM and Anovulation Santos et al., 2004

  26. Body Weight Loss in Dairy Cows Bar Peled et al. (1995)

  27. Dry Matter Intake for Dairy Cows Bar Peled et al. (1995)

  28. Estimates of Cycling Status • Cycling status during 1 to 3 wk before the end of the VWP (estimated by measuring blood progesterone) 793 first-lactation cows averaged 74.2% 1,126 multiple-lactation cows averaged 80.5% Stevenson, 2001

  29. Prebreeding Anestrus inLactating Holstein Cows Onset of First Ovulation Staples et al. (1990)

  30. Milking Frequency - Exp. 1 Bar-Peled et al. (1995)

  31. Milking Frequency - Exp. 2 Bar-Peled et al. (1995)

  32. Department of Animal Sciences and Industry Ontario Association of Bovine Practitioners Reproductive Symposium Thank you!

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