Review of Reproductive Review of Reproductive PhysiologyPhysiology

Jeffrey S. Stevenson, Ph.D.Jeffrey S. Stevenson, Ph.D.

Ontario Association ofOntario Association ofBovine PractitionersBovine Practitioners

Reproductive SymposiumReproductive Symposium

Department of Animal Sciences

and Industry

20 inches(508 mm) 20-24 inches

(508-640 mm)28-32 inches(711-813 mm)

32-36 inches(813-914

mm)36-40 inches

(914-1016 mm)

>40 inches(>1016 mm)

24-28 inches(640-711 mm)

Annual Precipitation

State of KansasState 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

Gonadotropin-Gonadotropin-Releasing Hormone Releasing Hormone

(GnRH)(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

Hypothalamus

Follicle-Follicle-Stimulating Stimulating

Hormone (FSH)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

Hypothalamus

• 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

Luteinizing Luteinizing Hormone (LH)Hormone (LH)

Hypothalamus

Theca cell Granulosa cell

Follicle basement membrane

Cholesterol

Pregnenolone

Progesterone

Androstenedione

(+)

Testosterone

Estradiol-17

Cholesterol

Pregnenolone

Progesterone

LH

LH

FSH

(+)

Estradiol-17Estradiol-17(blood) (follicular fluid)

(–)(–)

(+)

• 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

Estrogen Estrogen (Estradiol-17(Estradiol-17)) Ovary

ProgesteroneProgesterone

• Secreted by the corpus luteum• Induces development of uterine

endometrium• Prevents estrus and ovulation by

negative feedback inhibition of LH secretion

X X

OvaryCL

OvaryX

LH

E2

Onset of estrus

Onset of ovulation

27 hrEstrus

P4

0 2 4 0 2 4 0 2 4HoursHours Hours

E2

LH

E2

LH

E2

LH

Prostaglandin Prostaglandin

FF22

• 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) X

Ovary

CL

5 10 15

PGF2

21

LHLH

P4

Days of the Bovine Estrous Cycle

OvulationE

stru

s

FSH

E2

Metestrus Diestrus Proestrus

Ovulation

0

Est

rus

02468

1012141618

0 3 6 9 12 15 18 21Days of Cycle

Pro

gest

eron

e (n

g/m

L)

0

20

40

60

80

100

Lute

olyt

ic r

espo

nse

(%)

Progesterone Luteolytic Response DF1 DF2

The Estrous Cycle: Follicle Waves, The Estrous Cycle: Follicle Waves, Progesterone, and LuteolysisProgesterone, and Luteolysis

Normal Interval to EstrusNormal Interval to Estrus

02468

1012141618

0 3 6 9 12 15 18 21Days of Cycle

Fol

licle

dia

met

er (

mm

)

PGF2

Estrus

Shorter Interval to Estrus after Shorter Interval to Estrus after PGFPGF

02468

1012141618

0 3 6 9 12 15 18 21Days of Cycle

Fol

licle

dia

met

er (

mm

)

Est rus

PGF2

Longer Interval to Estrus after Longer Interval to Estrus after PGFPGF

02468

1012141618

0 3 6 9 12 15 18 21

Days of Cycle

Fol

licle

dia

met

er (

mm

)

Estrus

PGF2

GnRH-Induced Ovulation of GnRH-Induced Ovulation of Dominant FolliclesDominant Follicles

02468

1012141618

0 3 6 9 12 15 18 21Days of Cycle

Fo

llicl

e d

iam

ete

r (m

m)

Estrus

LH dependent

XX

XX

02468

1012141618

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

02468

1012141618

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Days postpartumStagg et al. (1995)

*

* *

*

Growth and Developmentof Dominant Follicles

(Suckled Cow)

Fol

licle

dia

met

er (

mm

)

Early Postpartum Follicular Early Postpartum Follicular WavesWaves

(Milked Cow)(Milked Cow)

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

Days postpartum

Fo

llicl

e d

iam

ete

r, m

m

Ovulation

Beam and Butler, 1996

Frequency of LH PulsesFrequency of LH Pulses

0

1

2

3

4

0 2 4 6 8 10 12 14 16

Hours

LH

( n

g/m

L)

Week 1 Week 2-3 Week 4-6

Weeks from energy balance nadir (0)

Cow 3 2 1 0 +1 +2 1 1 3 6 5 2 1 2 3 4 5 3 2 6 7 4 0 3 7 8 7 5 1 4 6 6 6 0 2 3 4 5 7 7 0 5 6 7 8 2 4 4 5 6 9 0 3 5 5 6 7 10 3 8

No. of LH Pulses/8 hr - Milked No. of LH Pulses/8 hr - Milked CowsCows

Canfield and Butler, 1990

First ovulation followed the last blood

collection series by 2.5 0.4

days.

Energy BalanceEnergy Balance

IntakeMetabolism

and Partitioning

Expenditures

Feed

Liver

Oxidizable metabolic

fuels

Adipose tissue

Fat stores

Reproduction

ThermoregulationCell

maintenance

Growth (NEG)

Milk yield (NEL)

Locomotion

(+) (–)

NEM

Energy Balance and First Energy Balance and First OvulationOvulation

Item

Mean of 17 dairy cows

SE

Body weight, kg (lbs) Calving Change during anovulation

729 (1607) 56 (123)

13 8

Energy balance, Mcal/day Anovulation

17.5*

4.2

Interval, days Calving to EB nadir EB nadir to ovulation Calving to ovulation

8.7 15.4 24.1

1.1 1.2 1.5

Zurek et al. (1995)

*Sufficient energy to produce

57 lb (26 kg) of milk/day

Uterine InvolutionUterine Involution

0

50

100

150

200

250

5 10 15 20 25 30 35 40 45 50

Days postpartum

Ute

rine

horn

dia

met

er,

mm

Gravid horn

Nongravid horn

Marion and Gier, 1968

E2

FSH

LH

IGF-I

Calving

Days postpartum

Ovulation

Nadir of EB

1015202530354045

2.25 2.50 2.75 3.00 3.25 3.50 3.75

BCS at 70 days in milk

Ano

vula

tion,

%

Body Condition Scores of Dairy Body Condition Scores of Dairy Cattle at 70 DIM and AnovulationCattle at 70 DIM and Anovulation

Santos et al., 2004

Body Weight Loss in Dairy Body Weight Loss in Dairy CowsCows

-80

-60

-40

-20

0

20

40

60

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

Weeks postpartum

kg

3x Milked

6x Milked

Suckled

Bar Peled et al. (1995)

Dry Matter Intake for Dairy Dry Matter Intake for Dairy CowsCows

0

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10

Weeks postpartum

kg/d

ay

3x Milked

6x Milked

Suckled

Bar Peled et al. (1995)

Estimates of Cycling StatusEstimates of Cycling Status

010

2030

4050

6070

8090

100

1 2 3 4 5 6 7 8

Herd-Year

% c

yclin

g

2-yr-old cowsOlder cows

• 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

Prebreeding Anestrus inPrebreeding Anestrus inLactating Holstein CowsLactating Holstein Cows

Item

Early Late Very late

No. of cows 25 14 15 Days to first ovulation 22 43 Days to first estrus 47 73 110 4% milk, kg/day 34 32 29 DM intake, kg/day 19 18 15 BW change, kg/day 0.8 0.8 1.2

Staples et al. (1990)

Onset of First OvulationOnset of First Ovulation

Milking Frequency - Exp. 1Milking Frequency - Exp. 1

Trait

Milked 3x

Milked 6x for 6 wk

Milked 3x + Suckled 3x

Days to 1st ovul. Days to 1st estrus Days to pregnancy 6-wk milk yield, kg/d Nadir of EB, Mcal/d Week at zero EB

26 46

112 35 9 6

37 76

184 43 14 10

48 48

100 50 19 8

Bar-Peled et al. (1995)

Milking Frequency - Exp. Milking Frequency - Exp. 22

Trait

Milked 3x

Milked 6x for 3 wk

Milked 6x for 6 wk

Days to 1st ovul. Days to 1st estrus Days to pregnancy 6-wk milk yield, kg/d 6-wk weight loss, kg Week at zero EB

22 45

105 35 24 6

30 61

148 40 29 -

39 75

189 42 32 10

Bar-Peled et al. (1995)

Thank you!

Department of Animal Sciences

and Industry

Ontario Association ofOntario Association ofBovine PractitionersBovine Practitioners

Reproductive SymposiumReproductive Symposium