1. PHYSIOLOGY OF REPRODUCTION
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
PHYSIOLOGY OF REPRODUCTION
REPRODUCTIVE CYCLES
Part I By
Dr. Abdul samik, M.Si.,Drh

2. The Reproduction Cycles
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
The Reproduction Cycles
Phenomena :
Puberty and sexual maturity
The breeding season
The estrous cycle
Postpartum sexual activity
Aging and fertility

3. Regulation of Reproductive Cycle
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Regulation of Reproductive Cycle
Environmental
Genetic
Physiologic
Hormonal
Behavioral
Psychosocial

4. Events of Reproduction
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Events of Reproduction
Puberty- Age at which reproductive organs become functional
Female- Reproduction process occurs within
Estrous cycle- Repetitive cycle occurring when pregnancy does not
Estrus- “Heat” or receptivity to mating
Fertilization- Egg & Sperm unite
Only real male contribution is the sperm
Gestation- Length of time of pregnancy
Parturition- Act of giving birth

5. Age of Puberty Cattle: 6 to 12 Months Sheep: 5 to 7 Months
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Age of Puberty
Cattle: 6 to 12 Months
Sheep: 5 to 7 Months
Swine: 4 to 8 Months
Horses: to 15 Months
Humans: 9 to 16 Years

6. What influences the onset of puberty in heifers?
Physiological events leading up to puberty
Endocrine and morphological events in peripubertal heifers are similar to the resumption of cyclicity post partum in mature cows.
Decreased negative feedback of oestradiol
Maturation of the hypothalamus
Increased frequency of release of LH pulses
Enhanced development of ovarian follicles
Enough oestradiol produced to induce behavioural oestrus and a preovulatory surge of gonadotrophins
Puberty is attained with the first behavioural oestrus that is accompanied by ovulation and development of a corpus luteum with a typical life span
What influences the onset of puberty in heifers?
Factors that can influence the pubertal rise in release of LH pulses are:
genotype
season of year when pubertal age is attained
growth or nutritional intake
social cues
treatment with exogenous hormones

7. Endocrine mechanisms of puberty

8. The Estrus Cycle When Heifer becomes sexually mature
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
The Estrus Cycle
When Heifer becomes sexually mature
ovaries function in a cycle activity
estrus period cycle days (21 days)
Estrous cycle – period of time from one estrus to the next

9. Breeding Season Monoestrous : dog, cat
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Breeding Season
Monoestrous : dog, cat
Polyestrous (cycle throughout year) : cattle, goat,
sheep, swine
Seasonal polyestrous (Decreasing light, Fall) : sheep, goat
Seasonal polyestrus (Increasing daylight, Spring) : horse

10. Length of Estrus Cycle Cattle: 19 to 23 Days Sheep: 14 to 19 Days
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Length of Estrus Cycle
Cattle: 19 to 23 Days
Sheep: 14 to 19 Days
Swine: 19 to 23 Days
Horses: to 37 Days

11. Duration of Estrus Phase
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Duration of Estrus Phase
Cattle: 6 to 27 Hours
Sheep: 24 to 36 Hours
Swine: 48 to 72 Hours
Horses: to 8 Days

12. Luteal phase.
A corpus luteum is formed under the influence of pituitary LH.
The function of the corpus luteum is to secrete progesterone, which reduces
the amount of the hormone oestrogen produced.
As long as the corpus luteum is functional, oestrogen is unable to trigger
formation of the follicle (a large fluid-filled sac containing the egg).
By day 18 the corpus luteum degenerates due to prostaglandin
(released from the uterus) and goes through a regression phase.
Associated with corpus luteum regression is a decline in progesterone

14. Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Follicular phase
Following the decline in progesterone, an increase in oestrogen (mainly oestradiol-17β) takes place and peaks before the onset of oestrus.
Oestrogen stimulates the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus.
GnRH stimulates the release of FSH and LH from the pituitary gland.
LH rises to a peak at the beginning of oestrus. FSH and LH stimulate the development of follicles in the ovary.

15. The follicle ruptures and releases the egg (ovulation).
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
One follicle predominates which secretes oestrogen and triggers a wide range of anatomical and physiological changes in the cow
All the changes ensure that if the cow is mated, the sperm will stay alive until one of the spermatozoa will effect fertilisation.
The follicle ruptures and releases the egg (ovulation).

18. Stage of heat Proestrus Estrus Diestrus Metestrus
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Proestrus
Estrus
Stage of heat
Diestrus
Metestrus

19. Stage of heat A. Proestrus day 19 -21
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Stage of heat
A. Proestrus
day
period for preparation of sexual activity

20. Stage of heat B. Estrus (heat, sexual desire)
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Stage of heat
B. Estrus (heat, sexual desire)
period of sexual activity, female permit mating
duration : hrs (heifer 15, cows 18hrs)

21. Signs of Estrus Primary Sign of Estrus Stands immobile when mounted.
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Signs of Estrus
Primary Sign of Estrus
Stands immobile when mounted.

22. Secondary Signs of Estrus
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Secondary Signs of Estrus
Behavioral
Bellowing
Increased Activity
Walking the fence line
Charging
Butting
Licking
Sniffing
Flehmen posture (inverted nostrils)
Circling
Chin-resting
Mounting

23. Physical Signs of Estrus
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Physical Signs of Estrus
Manure on flanks
Roughened tailhead
Loss of hair on tailhead
Abrasions on tailhead
Red vulva
Swollen vulva
Clear mucus discharge from vulva

24. Miscellaneous Signs of Estrus
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Miscellaneous Signs of Estrus
Depressed appetite
Depressed milk production
Frequent Urination
Metestrus bleeding : hours after estrus; too late to breed

25. Stage of heat C. Metestrus (after heat) day 1-5 of cycle
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Stage of heat
C. Metestrus (after heat)
day 1-5 of cycle
not permit mounting
50% cow , 90% heifer - metestral bleeding
corpus luteum begins to develop

26. Stage of heat D. Diestrus (between heat) day 5 - 19
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Stage of heat
D. Diestrus (between heat)
day
complete lack of sexual desire

28. LH and FSH During the Estrous Cycle
Progesterone
Hormone Concentration
FSH 5 10 15
Estrus
Days Relative to Estrus
Estrus

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

30. Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Mechanisms of luteolysis during the oestrus cycle of cows Luteolysis starts between days post oestrus in the cow. Bovine luteal tissue is usually not responsive to PGF2-alpha until after day 4 post oestrus
Two major mechanisms of luteolysis have been suggested:
1. Reduction of the blood flow in the corpus luteum (CL) A rapid decrease in luteal blood flow has been recently proposed as one of the main luteolytic actions of PGF2-alpha. It was demonstrated that the reduction in luteal blood supply 8 hours after prostaglandin injection was coincident with the onset of structural luteolysis, the first significant decrease in CL volume was seen.

31. Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
2. Direct action on luteal cells A direct action of prostaglandin on the luteal cells, resulting from both the decrease in cAMP synthesis normally produced in response to LH and the inhibition of the steroidogenic action of cAMP. These effects would be further amplified by a reduction in the number of receptors for LH. This theory is further supported by the result of a study that demonstrated that a prostaglandin-induced decrease in plasma progesterone concentrations occurs before a detectable decrease in both the volume of the CL and the luteal blood flow.

32. Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009

33. Follicular development in cattle
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Follicular development in cattle
Ovarian follicular growth and development in ruminants is characterised by two or three consecutive follicular waves per oestrous cycle.
Each wave involves the recruitment of a cohort of follicles and the selection of a dominant follicle.
The dominant follicle continues to grow and mature to the preovulatory stage while others undergo atresia.

35. Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009

37. Recruitment of follicular waves
Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Recruitment of follicular waves
The growth of follicular waves is initiated by a rise in circulating FSH. All follicles growing as a cohort contain specific receptors for FSH and depend on this gonadotrophin in their growth.
At this stage the growing follicles do not have a sufficient population of LH receptors to respond to a LH-like stimulation.
For this reason this stage of follicular growth is sometimes called FSH-dependent.

38. Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
For reasons not yet properly understood only one dominant follicle is selected from among the cohort recruited by the small rise in FSH. A defining characteristic of the dominant follicle appears to be its greater capacity for estradiol production.
Selection of the dominant follicle is associated with a decrease in FSH, FSH is maintained at basal levels. The selected future dominant follicle acquires LH receptors which allow it to continue growth in the environment of low FSH and increasing LH levels.

39. Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
It seems that by decreasing the FSH support, the selected follicle depletes subordinate follicles from their vital growth stimulant while it benefits from both the low FSH and growing LH stimulation

40. Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009
Selected dominant follicle and ovulation
Following its selection, DF growth, oestrogen activity and lifespan are controlled by the LH pulse pattern. In response to maximum concentrations of oestrogens produced by the dominant follicle a massive LH release takes place. It is called a pre-ovulatory LH surge or peak and acts as the direct stimulation of ovulation