Female ReproductionAnatomy and Physiology

Ryon Walker

PhD Grad Student,CSU – Dept. of

Animal Sciences

Cow’s Reproductive CycleCow’s Reproductive Cycle

ReproductiveTract

Follicles andNew Corpus

Luteum

Mature CorpusLuteum

Ovary

Female Gonad (sex gland)Site of Action for LH, FSH, PGF2alphaTransient Organs– Follicle– Corpus Luteum

OvaryOvaryGraffianGraffian Follicle (dominant follicle)Follicle (dominant follicle)-- Fluid filled sac Fluid filled sac –– oocyteoocyte developsdevelops-- OocyteOocyte suroundedsurounded by theca and by theca and granulosagranulosa cellscells-- OvulationOvulation

Corpus Corpus Luteum Luteum (yellow body)(yellow body)-- Develops at site of ovulationDevelops at site of ovulation-- LutealLuteal cells develop from theca and cells develop from theca and granulosagranulosa

cellscells-- Remains if female is pregnantRemains if female is pregnant

Ovarian Structures

HormonesHypothalamus– Gonadtropin Releasing Hormone (GnRH)

Posterior Pituitary– Luteinizing Hormone (LH)– Follicle Stimulating Hormone (FSH)

Ovary– Estrogen – Progesterone

Uterus– Prostaglandin F2α (PG)

Estrous CycleEstrous CycleAlternating domination of Alternating domination of eithereither::

-- estrogen from follicleestrogen from follicle-- Progesterone from corpus Progesterone from corpus luteumluteum

Follicle ProductionFollicle Production

Pituitary gland releases:Pituitary gland releases:-- FSH for initiating growth of folliclesFSH for initiating growth of follicles-- LH for steroid hormone production from LH for steroid hormone production from

folliclefollicleGraffianGraffian follicle produces Estrogen follicle produces Estrogen Corpus Corpus LuteumLuteum produces Progesteroneproduces Progesterone

Estrous CycleEstrous CycleLutealLuteal Phase (d 1Phase (d 1--18)18)Follicular Phase (d 18Follicular Phase (d 18--21)21)

Estrous CycleEstrous Cycle

Estrus (d 0)Estrus (d 0)Ovulation (d 1)Ovulation (d 1)MetestrusMetestrus (d 1(d 1--5)5)DiestrusDiestrus (d 5(d 5--17)17)ProestrusProestrus (d 17(d 17--21)21)Estrus (d 0)…….Estrus (d 0)…….

Follicular Luteal

Follicular

Estrus (day 0)Estrus (day 0)

Follicle maturesFollicle maturesEstrogen increases as follicle maturesEstrogen increases as follicle maturesIncrease estrogen = increase Increase estrogen = increase GnRHGnRHIncrease Increase GnRHGnRH = increase LH= increase LHLH surgeLH surgeEstrus (standing heat)Estrus (standing heat)OvulationOvulation

Ovulation (day 1)Ovulation (day 1)

Oocyte (egg) releaseInduced by LH surge28 hours after first heat

MetestrusMetestrus (day 1 (day 1 –– 5)5)

Corpus luteum formationGrowth and development of follicular waveIncrease in progesterone production– Non responsive to PG– Prepares uterus to accept fertilized egg– Maintains pregnancy and prevents heat– Presence of fetus keeps CL alive

DiestrusDiestrus (day 5 (day 5 –– 17)17)

Mature Corpus LuteumMaximal progesterone productionGnRH inhibited by progesteroneMaternal recognition of pregnancy

Unfertilized cow:– PG kills CL and stops producing progesterone

around day 16 - 18

ProestrusProestrus (day 17 (day 17 –– 21)21)Prostaglandin production by uterusLuteolysis– Decreased progesterone production– CL regresses

GnRH no longer inhibitedFinal maturation of dominant follicleIncreased estrogen

..Estrus (d 0) … Ovulation (d 1)....Estrus (d 0) … Ovulation (d 1)..

Estrous Cycle

0 2 4 6 8 10 12 14 16 18 20 1

Hor

mo

ne L

evel

Progesterone (P4)

Estradiol (E2)

Day of Estrous Cycle

New CLForming

Mature CL Present Fol. Size& CL Size

Sperm ActivitySperm Activity

Sperm travels and waits in oviduct (Sperm travels and waits in oviduct (ampullaampulla))-- Sperm life span in female tract (24 hrs.)Sperm life span in female tract (24 hrs.)-- Need sperm in tract hours before egg Need sperm in tract hours before egg

releasedreleased-- Egg life span in female tract after release Egg life span in female tract after release

(8 (8 -- 12 hrs.)12 hrs.)-- Ovulation occurs 28 hours after heatOvulation occurs 28 hours after heat

Approximately 6% of beef cattle (cows) in Colorado are artificially inseminated.About 18% of heifers in the US are artificially inseminated.

Why?– According to a national survey the #1

reason for not using synchronization or AI “Time and Labor.”

Obstacles

- Lack of producereducation.

- Economics of time and labor.

- Inadequate Facilities- Cost- Relative poor conception rates.- Lack of information

Benefits of SynchronizationTighter breeding and calving seasonDecreased time needed for estrous detectionImproved calf uniformity.Increased time for post partum recoveryInducement of estrous cycles, anestrous cowsIncreased calf performance.

Classes of Synchronization Drugs

1) Prostaglandins

2)Progestins

3) GnRH

Prostaglandins

PGF2α

Causes regression of the corpus luteumStops progesterone block on estrogen and LH release so follicle can mature and ovulate.

Prostaglandins

Cattle with a functional CL at time of PG injection will exhibit estrus 2 to 7 days later.Will only affect cattle in diestrus or the luteal phase.

ProgestinsSynthetic progesterone - prevents estrus from occurring.Most cows exhibit estrus 2-5 days after removal of progestins.Administration:– Oral administration (MGA)– Intravaginal insert (CIDR)– Implant (Syncro-Mate B)

GnRH

Causes release of LH and FSH.LH and FSH act on the ovary to stimulate

follicular development andovulation orregression of dominant follicle.

Manipulation of dominant follicle with MGA Select Synch

Follicle StudyDominant Follicle Corpus Luteum

Follicle StudyDominant Follicle Corpus Luteum

Red Cow Left Ovary

0

2

4

6

8

10

12

14

16

18

20

22

14 15 16 17 18 19 20 0 1 2 3 4 5 6 7 8 9 10 11 12 13

Day of Estrous

Siz

e (m

m)

Follicle IFollicle IIFollicle IIIFollicle IV

Synchronization StudySJBRC – 2003

Objective– Synchronize heifers to increase fertility with a

new progestin (CIDR)Heifers from three locations– San Juan Basin Research Center (CO; 39 head)– Beef Improvement Center (WY; 125 head)– Quinn Cattle CO (SD; 211 head)

Protocol

• Control (CON) - Give nothing at breeding

• Treatment (Trtmt) - Give GnRH at breeding

Day 0 Day 7 Day 9

CIDR Insert

CON54 h Mass Mate

CIDR InsertGnRH

CIDR RemovalPG Trtmt

CIDRs“T” shaped device (insert)Wings collapse to form

a rod and inserted intothe applicator.

Nylon backboneProgesterone

impregnated intosilicone skin.

1.38 g progesterone

CIDR ApplicationCIDR is applied into the vagina with anapplicator gun and released

CIDR is removed by pulling on tail.Progesterone levels rise dramatically within 1 hour.

Follicle Study – SJBRC 2003Objective– Measure dominant follicles at breeding– Determine if ovulation occurs

Pregnancy Results

a52.6 %

a55 %

a54 %

a56.5 %

b40.4 %

a54.2 %

0

10

20

30

40

50

60

70

Preg

nanc

y R

ate

TAI,

%

Colorado (CO) Wyoming (WY) South Dakota (SD)

CONTRMT

Follicle ResultsFollicle Size at Breeding

010203040

50607080

90100

Preg

nanc

y Rat

e, %

10 - 11.9mm

12 - 13.9mm

14 - 15.9mm

16 - 18 mm

FollicleDiameter

Follicle ResultsOvulation

0102030405060708090

Preg

nanc

y R

ate,

%

Control Treatment

Ovulation, %Pregnancy Rate, %