Understanding Postpartum Anestrus

and PubertyDr. Jack C. Whittier, Colorado State UniversityDr. Jim Berardinelli, Montana State University

Dr. Les Anderson, University of Kentucky2008 Robert E. Taylor Memorial Symposium

Anestrus?

• Anestrus is the primary factor reducing reproductive efficiency in beef cow-calf operations.

• Anestrus can be defined as the lack or absence of the expression of estrus.

• Anestrus occurs annually; heifers are anestrus prior to puberty and anestrus occurs in cows after each calving.

Causes of Anestrus

• Before puberty – (prepuberal anestrus)• After calving – (postpartum anestrus)

– Biological protection for dam and offspring• Lactational• Nutritional

– If the environment is not suitable for the dam, why bring a competing calf into this environment

– Every other year calving in harsh environments• Seasonal (ewe, mare)• Pregnancy

Factors Contributing to Infertility

• General Infertility– Biological Ceiling– 25% to 30% effect

• Uterine Involution• Short Estrous Cycles• Anestrus

– Potential for manipulation through management

Relationship of Fertility to Time After Calving

Short et al., 1990

Incidence of Anestrus* in US Beef Cattle at Start of Breeding Season

0

10

20

30

40

50

60

Postpartum Cows Yearling Heifers

Lucy et al., 2001

% A

nest

rus F

emal

es

Range 17-67%

Range 6-81%

14.7 months of age

851 cows at 6

locations Nursing Calves

56 days postpartum

724 heifers 5 locations

*Based on blood samples for progesterone

35

47 45

6861

0

15

30

45

60

75

1994 1995 1996 1997 1999

Year

% o

f all

cow

s

% Cyclic

Percent of Cows Cyclic by Year (~ 60 d postpartum)

(Jackson Branch of the OSU Ag Experiment Station, Jackson, OH)

What Is Anestrus Physiologically?

Postpartum Anestrus in Beef Cows

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75

Stru

c tur

e D

i am

eter

Days Relative to CalvingCalving First

Estrus

Progesterone

* *

Anestrus45 to 90+ days in US Beef Cows

1st DFEstrogen inhibitory!

-55 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 60 65 70 75

“Depth” of Postpartum Anestrus in Beef CowsH

orm

one

Co n

cen t

rat io

n

Days Relative to First Estrus First Estrus

Progesterone

Peri- EstrusAnestrus

Increasing “Depth” of Anestrus

Estrogen inhibitory! Estrogen stimulatory!

GnRH/CIDR Protocols Effective

Factors Regulating the Length of Anestrus

• Presence of the calf– Initiates anestrus

• Body Condition Score (BCS)• Parity• Days Since Calving• Other factors include dystocia, health, and

calving season (fall vs. spring)

Presence of the Calf

Presence of the Calf• Presence of the calf initiates anestrus

– Establishes the negative feedback of estrogen on the hypothalamus

– Results in low LH pulse frequency– Exact mechanisms unknown but both the physical

contact of the calf (nursing) and the mere presence of the calf at side are involved

• Short-term calf removal (48 h) has been shown to be an effective method to induce estrus– GnRH/CIDR synch protocols appear to mimic this

response

Stevenson et al., 1994

• Is it presence of calf, nursing, or other?• Four treatments:

– Mastectomized, calf weaned at birth– Mastecomtized, calf restricted to non-inguinal

contact (head and neck of cows – restricted by pen and panel barriers)

– Mastectomized, unrestricted calf presence– Udder intact, unrestricted calf presence

Stevenson et al., 1994

• Results– Unrestricted presence of calf prolonged anestrus in

both intact and mastectomized cows– A cow must receive stimuli resembling normal

suckling to prolong anestrus whether intact or mastectomized

Presence or Absence of the Bull

• Bull effect• Presence of male (boar, ram)• Several studies indicate a positive response to

bull exposure– Intact– Sterilized– Androgenized cows or steers

• Does putting the bull with the cows at the beginning of the breeding season have the same effect?

Jim Berardinelli, Ph.D.

Department of Animal and Range SciencesMontana Agricultural Experiment Station 

Montana State University‐Bozeman  

17

Biostimulatory effect of bulls (MSU & Others)

Presence of bulls accelerates resumption of estrous cycles; decreasing length of anestrus.

In bos taurus & indicus cows

18

Table 1.  The biostimulatory effect of bulls in primiparous Table 1.  The biostimulatory effect of bulls in primiparous 

and multiparous cows (adapted from Custer et   al., 1990; and multiparous cows (adapted from Custer et   al., 1990; 

and Stumpf et al. 1992, respectively).and Stumpf et al. 1992, respectively).

Primiparous 

cowsMultiparous 

cows

Variable NE BE diff NE BE diffPostpartum 

interval to 

anestrus, d 82 ± 9 a 64 ± 6 b 18 58 ± 2 a 44 ± 2 b 14

a,b

Means that lack a common superscript differ (P <

0.05).

19

What we know about the biostimulatory effect  of bulls (MSU)

1.Caused by pheromone(s) produced by bulls  (Berardinelli and Joshi, 2005b).

2.Does not appear to work before 35 d after  calving in suckled cows (Fernandez et al., 1993.

20

What we know about the biostimulatory effect  of bulls (MSU & Others)

3.Works better as time after calving increases  after 35 d (Berardinelli and Joshi, 2005a).

4.Bulls > 18‐mo‐old and “androgenized”

cows  have same affect as mature bulls (Cupp et al.,  1990; Burns and Spitzer, 1992).

21

What we know about the biostimulatory effect  of bulls (MSU)

5.Intermittent exposure does not work  (Fernandez et al., 1996).

6.Twelve hour‐exposure does work (Berardinelli  and Joshi, 2005b).

22

What we know about the biostimulatory effect  of bulls (MSU & Others)

7.Fence‐line contact under certain conditions will  work (Fike et al., 1996; Berardinelli and Tauck, 

2007).

8.Continuous exposure to bulls urine does not  work (Tauck et al., 2006)

23

…it appears to enhance pregnancy when used in conjunction with GnRH‐ and progesterone‐based estrous synchronization protocols that incorporate fixed‐time AI (Berardinelli and Tauck, 2007; Tauck and Berardinelli, 2007). …effect of bulls not only increases the number of suckled cows that begin cycling before the breeding season, but that AI pregnancy rates are significantly improved by the biostimulatory effect of bulls. 

24

Body Condition

Body Condition Score (BCS)

• Body Condition Score is an estimate of the degree of fatness of an animal– 1 = emaciated– 9 = extremely obese

• Estimate of available energy stores

Uses of Nutrients and Energy

Basal MetabolismActivityGrowth

Basic energy reserves (fat)PregnancyLactation

Estrous cyclesAdditional energy reserves (BCS = 4-5)

Unnecessary energy reserves (BCS > 6)

Nutrients

Influence of BCS at Calving on Anestrus

8071

5949

2542

0%

20%

40%

60%

80%

100%

<3.5 4 4.5 5 5.5 >6

Body Condition Score

% C

yclin

g

3371,002726481157 188

Source: Stevenson et al., 2003

Interaction of BCS at Calving and Postcalving Nutrition

Postcalving Nutrition

0

20

40

60

80

100

1 2 3 4 5 6 7 8 9 10Body condition score at calving

Day

s to

firs

t pos

tpar

tum

est

rus

HighAdequate (100% NRC)Low

Source: Short, 1990

Parity

• Young cows (2 year old suckled cows) simply require 20-30 more days to resume estrous cycles

• Recommendation has always been to calve first parity cows 20-30 days before the mature cow herd– Stevenson et al., 2003

Parity Days PP Percent Cyclic1 86 552 68 64

Uses of Nutrients and Energy

Basal MetabolismActivity

Growth

Basic energy reserves (fat)PregnancyLactation

Estrous cyclesAdditional energy reserves (BCS = 4-5)

Unnecessary energy reserves (BCS > 6)

Nutrients

Influence of Days Since Calving

Influence of Days Since Calving on Anestrus

9

25

44 4555

6270

62

01020304050607080

<30 31-40 41-50 51-60 61-70 71-80 81-90 >90

Days Postpartum

% C

yclin

g

Source: Stevenson et al., 2003

Regulation of Anestrus

Hypothalamic‐Pituitary Axis (HP): Control  Unit for Reproduction (Adapted from Senger, 2003)

..

Brain

Hypothalamus

Pituitary gland

36

General Physiological Mechanism for Anestrus :  Hypothalamic‐Pituitary Axis

(Adapted from Senger, 2003)

LH

Anestrus 

conditions

Cycling 

condition

37

HypothalamusGnRH “Pulse Generator”

Anterior Pituitary

Other CNS Signals

+ ‐

GnRH

LH pulse 

frequency

GnRH

LH pulse 

frequency

Metabolic Signals&

“Basics”

of System: Cycling vs. Anestrus

Ovary = 

“quiet”Ovary = 

“active”

38

Anestrus/Anovulation

Function of HypothalamusGnRH pulse Generator

PituitaryLH secretion

Low freq./high amp GnRH

LH:Low freqhigh 

amp 

Estradiol‐17b

Lactation‐cow/calf bond Nutrition/BCSBull Biostimulation 

High freq./low amp GnRH

Estradiol‐17b

LH:High freqLow amp

Ovary

Time after calving

Metabolic Signals&

Pregnancy & parturitionLactation‐cow/calf bond Nutrition/BCSOther CNS Signals

‐+

Normal Follicular 

Development/Estrus/Ovulation

Ovary

39

Puberty

• Puberty is the occurrence of estrus and ovulation followed by the formation of a CL that leads to an estrous cycle of normal length.

• To MAXIMIZE fertility, heifers need to reach puberty by12-13 months of age.

HypothalamusGnRH “Pulse Generator”

+

LH pulse frequency

Anterior Pituitary

Other CNS Signals

‐

GnRH GnRH

LH pulse frequency

Puberty &Estrous cycles

Interactions,i.e., growth rate

Metabolic Signals&

Peripuberal

period

Prepuberal“anestrus”

Sensitivity to Estradiol

Ovary:follicular devel.  

maturation, 

ovulation

Ovary:  lack of 

follicular devel.,  

maturation, ovulation

Environmental FactorsNutrition

Body composition?Season of birth

Social cues: pheromone(s)Hormone  therapy

Stress

(+,‐)

Genetic FactorsBreedSire

Heterosis

(+,‐)

41

“Depth” of Puberty in HeifersH

orm

one

Co n

cen t

rat io

n

Days Relative to First EstrusFirst

Estrus

Progesterone

Peri- PubertyPrepuberty

Increasing “Depth” of Anestrus

Estrogen inhibitory! Estrogen stimulatory!

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 -5 0 5 10 15 20

Summary

• Anestrus is the major factor regulating reproductive efficiency.

• Induction of estrus in anestrous cows is essential to maintaining a high reproductive rate.

• Estrus synchronization protocols for anestrous females MUST include a progestin (CIDR, MGA, or GnRH).

• Bottom Line: Adequate nutrition will solve a high percentage of anestrus problems – both cows and heifers