1. Reproductive Physiology
What in the World is Going on in There!

3. GnRH

4. GnRH
LH and FSH +

5. Ovarian Structures Follicles Corpus Luteum (CL)
Balloon-like structures
Produces estrogen
Contain the oocyte (egg)
Corpus Luteum (CL)
Solid structure
Produces progesterone
The ovary contains two main structures, follicles and the corpus luteum called the CL. Read the slide.

6. Waves of Follicular Development
Ovulation
Ovulation
1st
2nd
Wave
Wave
Hormone Concentration 5 10 15
Estrus
Days Relative to Estrus
Estrus

7. The Ovarian Cycle – Growth of the CL
Estrus
Estrus
At heat, the a large follicle exists on the ovary. This follicle produces large amounts of estrogen that stimulates heat. Estrogen also causes the rupture of the follicle and the formation of a CL. During the cycle the CL grows until around days after heat. If the female is NOT pregnant, prostaglandin is released and the CL dies. Once the CL begins to die another follicle begins to mature, produce large amounts of estrogen and the next heat results.

8. GnRH
LH and FSH +
Estrogen +
Progesterone -

9. GnRH
LH and FSH +
Estrogen +
Progesterone -
PGF -

10. The Estrous Cycle in CattleLH
1st
Progesterone
2nd
Wave
Wave
Hormone Concentration
Estrogen
FSH 5 10 15
Estrus
Days Relative to Estrus
Estrus

11. General Repro Statistics
Estrous Cycle Length = 21 days; range 17-24
Length of estrus = 12 hours; range 6-24
Ovulation = hours after the end of estrus or 30 hours after beginning of estrus; range 18-48
Gestation length = 283; range

12. Estrus Synchronization

13. Estrus Synchronization
Methods to synchronize estrus were developed to enhance the use of AI in beef and dairy cattle
Daily observation of estrus is labor intensive and inefficient
Choosing the right protocol is the key to success

14. Factors Impacting Your Choice
Cows – how many are likely anestrus?
Anestrus is a reproductive state in which cows are NOT coming into estrus
Anestrus occurs after each calving
Normally mature cows are anestrous for days and young cows for days.
How long a cow is anestrus is influenced by her:
BCS
Number of days since calving
Age (how many two year olds)
The proportion of cows that are anestrous dictates which program is used.

15. Factors Impacting Your Choice
How much time and labor are you willing to dedicate to being successful?
Do you work full time?
Do you have help?
Can you schedule the technician?
Do you have good facilities?
Head catch, chute, alley, sorting tubs
Sort pens, holding pens

16. Pharmaceuticals Used GnRH (gonadotropin-releasing hormone)
Action: Stimulate rupture of a follicle which results in the release of the egg, formation of a corpus luteum, and resets follicle growth
Used at the beginning AND end of most protocols
Products
Cystorelin
Fertagyl
Factrel
Ova Cyst
Generic

17. Pharmaceuticals Used Progestins
Biological Action: Imitates the CL, inhibits estrus if the cows have started cycling, induces estrus in anestrous cows
Products
MGA
Feed additive
Feed at a rate of .5 mg/hd/day
CIDR

18. Pharmaceuticals Used Prostaglandins
Action: Stimulate the death of the CL and decreased progesterone so that the cow can come into estrus
Typically given at the end of the protocol
Products
Lutalyse
Estrumate
In-Synch

19. Heifer Systems
With heat detection

21. With less heat detection
Heifer Systems
With less heat detection

25. Heifer Systems
With no heat detection

29. 5-day PG + CIDR
66-72 hr

30. Cow Systems
With heat detection

31. If Most of the Cows are Cyclic….

32. If Most of The Cows Are Anestrus…

33. With limited heat detection
Cow Systems
With limited heat detection

35. Cow Systems
With no heat detection

37. Resynch GnRH + TAI GnRH GnRH PG Heat Patch Breed Red Patches CIDR CIDR7 10 24 31
32-35
14 days

38. Results Conception Rate Resynch 45-75%
No real difference between protocols
Resynch
70-85% AI after 2 rounds
85-90+% after 3 rounds

39. Summary Tons of systems = information overload! Systems I use
Only have time for timed-insemination
Heifers – 5-day PG + CIDR
Cows – 7-day CO-Synch + CIDR