Postpartum Anestrus and its Management in Dairy Cattle

Postpartum Anestrus and its Management in Dairy Cattle

Introduction

Postpartum anestrus refers to a condition where cows have

not been observed or reported in estrus for several weeks

after calving, often to the end of the voluntary (elective)

waiting period, in dairy cattle. While a short period of ovarian

inactivity during the immediate postpartum period is normal,

extended anestrus in nonsuckled cattle such as dairy cows

could have negative ramifications on the timely reestablishment

of pregnancy.

Clinical findings

they have not been seen in oestrus

since the time of calving.There are, however, other

animals which relapse into anoestrus after having

started cycling.These may be identified as animals

that have ceased cycling, or may only be discovered

when they are presented for pregnancy diagnosis.

On examination per rectum

, the ovaries of affected cows are small, quiescent and usually flat and smooth .

Depth of anoestrus can be gauged, to some extent, by the

size of the ovaries and the degree of development of the structures within them (Nation et al., 1998).

Thus, cows with very small, inactive ovaries, which

are devoid of any significant structures (i.e. no palpable

follicles or luteal structures), are considered

to be in a greater depth of anoestrus than are those

with larger ovaries containing palpable follicles.

Differentiation must be made from other causes

of anoestrus, but the presence of a large corpus

luteum within an ovary would easily permit detection

of animals that were pregnant or had endometritis.

or pyometra, while the presence of cystic

ovarian disease is also characterised by enlargement

of the ovary.

Ultrasonographic examinationof the ovaries

per rectum permits identification of ovarian structures

for a greater proportion of the oestrous cycle

than does simple manual palpation but, even so,

there are stages of the cycle when differentiation

between the cyclic and anoestrous ovary is not

achievable

If there is sufficient time before the start

of the breeding period, differentiation can eventually

be achieved by waiting 10 days; at this time the

ovary of a cyclic cow will have a mid-cycle corpus

luteum, whereas the anoestrous animal will remain

with inactive ovaries.

Milk or blood progesterone determinations

Are helpful in confirming a diagnosis; two samples can

be taken at 10-day intervals or a single sample 10

days before a rectal palpation is made (Boyd and

Munro, 1979). The more frequent use of milk

progesterone assays from 25 days postpartum

until the first service has been shown to be costeffective

(McLeod, 1990).

Classification of postpartum anestrus

Postpartum anestrus can be classified into different types

based on either ovarian follicle dynamics or progesterone

profiles.

Categorizing anestrus based on ovarian

follicular dynamics

The classification of anovulatory conditions in cattle based

on three functionally critical follicular diameters relating

to emergence (~4 mm), deviation (~9 mm), and ovulation

(10–20 mm) has been proposed

With the above

classification as the basis, four types of anestrus, types I to

IV, were described by Peter et al

In type I anestrus, there is growth of follicles up to

emergence but no deviation occurs resulting in lack of selection

of a dominant follicle. This type of anestrus is presumed due

to extreme malnutrition, which could exert a negative effect

on FSH production suppressing follicular growth, although

other factors could also be involved. Ovaries under this type

may be described as either “inactive” or “smooth” as a

reference to the lack of palpable ovarian structures during

reproductive examinations per rectum.

An Israeli study  from the 1980s reported an incidence of 8.5% inactive ovaries from 7751 lactations.

While type I anestrus is not widely seen in dairy cattle of developed countries, this type of anestrus could be more prevalent in regions of the world where balanced energy-dense rations are unavailable to dairy cattle.

In type II anestrus both follicular deviation and growth

occur, followed by regression, in some cases, after a follicle

attained dominance. Regression of a dominant follicle is

usually followed by the emergence of a new follicular wave,

2–3 days later. In this type of anestrus, there may be

sequential emergence of follicular waves prior to the

eventual occurrence of the first ovulation. Up to nine waves

of follicular growth have been reported in one study.

In type III anestrus, deviation, growth, and establishment

of a dominant follicle takes place, but the dominant follicle

fails to ovulate, becoming a persistent structure which may

either linger as an anovular follicle or continue to grow and

develop into a cystic follicle

Anovular follicles are considered

different from cystic follicles because in cows with the

latter condition there is disruption of the feedback mechanisms

in the hypothalamic–pituitary axis.

The secretory pattern of LH in cows with cystic ovarian follicle is quite different from that in normal cyclic cows in that mean concentrations of LH, frequency of LH pulses, and amplitude of LH pulses are all higherin addition, in cows with an actively

growing cystic follicle, the estradiol concentration is also significantly higher

A cystic follicle that is growing actively usually exerts dominance, suppressing the growth of other follicles.

Retrospective analysis of data from twice-weekly ultrasonography, from 7 to 35 days after calving, on eight lactating dairy cows that developed cystic ovarian follicles, a

first-wave dominant follicle became cystic in seven cows,

and a second-wave dominant follicle became cystic in one

cow. No other follicle greater than about 5–6 mm diameter

was detected on either ovary of cows until the cystic follicle

turned over. In five cows, the cyst persisted until (possibly

beyond) day 35; in two cows, the initial cystic follicle was

replaced by another one; in one cow two follicles from the

second follicular wave became dominant around day 30 at

which time the original cyst had regressed to below 20 mm

diameter giving way for both dominant follicles to ovulate

(Divakar J. Ambrose, personal observations).

In type IV anestrus, a dominant follicle ovulates and forms

a CL, but the luteal phase is prolonged due to the absence of

timely luteolysis followed by CL regression. Aberrant follicular

growth patterns resulting in the absence of an estrogenic

dominant follicle at the ideal time to trigger luteolysis could

be a reason for this condition of persistent CL.39

Categorizing anestrus based on progesterone

profiles

Cows can also be classified into different categories of

Anestrus based on progesterone measured in milk or blood

at least on a twice-weekly basis. Using twice-weekly

measurement of progesterone in milk fat on 334 dairy cows

from six herds, Opsomer et al.45 reported that 51% of the

cows had a normal progesterone profile with the first rise in

progesterone occurring before 50 days after calving, followed

by regular cyclicity. Among the remaining population,

21.5% of the cows had delayed cyclicity (anestrus for the

first 50 days after calving, characterized by consistently low

progesterone during that entire period), 21.5% had prolonged

luteal phase (progesterone remained elevated for

>20 days without a preceding insemination), 4% had cessation

of cyclicity (normal cycles interrupted by at least

14 days of consistently low progesterone concentrations),

0.5% had short luteal phases (characterized by more than

one luteal phase, excluding the first luteal phase, that was

shorter than 10 days’ duration), and 1.5% of the cows had

irregular progesterone profiles (atypical profiles, that did

not belong to any of the previously described categories).

General strategies to diagnose and minimize

the impact of anestrus

1. Perform body condition scoring (BCS). Assessing BCS of cows will provide an indirect indication of whether cows are

meeting their energy needs adequately. Performing BCS of

the whole herd, paying particular attention to close-up dry

cows, fresh cows and cows in the breeding group, would

be of great value. Close-up dry cows that are in high body

condition (BCS >3.5/5) should be considered high risk for

metabolic disorders and anestrus. A disproportionately

large number of cows beyond 60 days in milk with poor

body condition (BCS <3.0/5) should also be considered a

problem as the prevalence of anestrus will be higher in

those herds. Herdsmen should be educated on the importance

of BCS, properly trained in the technique, and

encouraged to perform condition scoring every 2 weeks,

or at least every month, and keep a good record of the

scores. Inseminating cows in poor body condition must be

avoided and breeding delayed until a threshold BCS is

attained, as low BCS cows have poor conception rates and

a much higher risk of pregnancy loss.

2. Perform gait (locomotion) scoring. Herds where gait scoring

is not performed should be encouraged to do it, routinely,

to identify cows that are showing early signs of

lameness. Periodic gait scoring, regular hoof trimming,

and the use of foot baths must be encouraged to keep

lameness in check. Lame cows will often be the last ones

to reach the feed bunks and they are less motivated to

leave the comfort of their stall to access feed frequently.

As a result, they consume less feed predisposing them to

an increased risk of negative energy balance and anestrus.

Grouping cows with even early signs of lameness

and feeding them separately would be one approach to

improve dry matter intake in these cows, mitigating negative

energy balance.

3. Improve the efficiency of estrus detection. The use of tail

chalk or tail paint to improve estrus detection efficiency

is one of the simplest strategies that could be implemented

in herds of any size. Using three different colors

to mark fresh cows (to determine cyclicity), cows at the

end of the elective waiting period (to be flagged for

insemination), and previously inseminated cows (for

return service) would provide an efficient yet simple

system for systematically detecting cows in estrus. In the

breeding group, tail chalk scores should be recorded

daily for this system to be effective and fresh chalk

applied at least once weekly. Applying tail chalk or tail

paint on fresh cows 30–40 days before the end of the elective

waiting period is highly recommended. If tail chalk

remains largely intact until the end of the elective waiting

period, the cow is probably anestrous. This is because

“standing estrus,” which is essential for tail chalk to be

removed completely, is only exhibited by 50% of lactating

dairy cows in estrus36 at 9–12 weeks after calving

4. Use of ultrasonography. Transrectal ultrasonography is an

excellent diagnostic tool for the objective assessment of

ovaries, and must be used wherever practical during routine

reproductive examinations. Examining the ovaries by

ultrasonography at approximately 5 weeks after calving

provides great diagnostic value. Diagnosis of the anestrous

condition based on ovarian ultrasonography must

involve at least two consecutive examinations performed

at an interval of 7–14 days.82 Although two examinations

at a 7–14 day interval are preferred, a single ultrasound

examination has fairly good diagnostic value

5. Monitoring progesterone profiles. Albeit somewhat expensive, monitoring milk progesterone concentrations can be

a reliable approach for assessing the prevalence of anestrus

in dairy herds. During the early postpartum period

progesterone concentrations will be very low and will

continue to remain so until first ovulation occurs.

Progesterone will rise following the first ovulation but

will decline after a few days as the first luteal phase is typically

short-lived. The second and later luteal phases will

be of normal duration. Dairy cows relapsing back into

anestrus after the first postpartum ovulation has been

documented regular measurement of progesterone can

assist in determining the patterns of cyclicity in dairy

herds. The recently introduced Herd Navigator® system

(DeLaval International) has the capability to measure

in-line milk progesterone concentrations at the milking

parlor. It has been claimed that Herd Navigator detects

consistently above 95% of all estrus events including

silent heats and is very useful in the detection of postpartum

anestrus, pregnancy, and ovarian cysts.84 While

this is a welcome addition to the reproductive management

6. Measuring plasma metabolites. Measuring plasma NEFAs, an

indicator of negative energy balance and the early diagnosis of subclinical ketosis, particularly during the first

week  can assist in the early identification of cows at risk

Nutritional intervention

Interactions between nutrition and reproductive processes

are complex and it is often difficult to precisely study

effects of specific nutrients on ovarian function.

Excessive energy intake during the close-up dry period can result in changes in metabolism that may predispose cows to

decreased dry matter intake and higher circulating NEFAs

during the immediate peripartal period therefore monitoring

feed intake in close-up dry cows is also quite

important.

Specific nutritional or nutraceutical interventions to

reduce the incidence of postpartum anestrus may include

feeding diets high in starch or daily oral administration of

monopropylene glycol during the postpartum period.

Adding starch or oilseeds enriched in long-chain fatty acids

such as linoleic or linolenic acid  during the prepartum

period have also reduced the interval from calving to first

ovulation.

 One study  reported that cows that consumed an

energy-restricted (80% of calculated requirement) diet during

the entire dry period had lower NEFA concentrations

and higher dry matter intake during the postpartum period

than cows consuming 160% of predicted energy requirements

during the dry period. Thus, several options exist for

dietary manipulations that could mitigate negative energy

balance and reduce anestrus. However, results are variable

and research findings may not always translate into practical

or economic solutions under commercial herd settings.

Therapeutic intervention

Progesterone

Treating anestrous cows with progesterone increased LH pulsatility, estradiol concentrations, and LH receptors in granulosa and theca cells of the preovulatory follicle .

Thus intravaginal progesterone devices can be quite effective in treating true anestrus.

When progesterone is used alone, a treatment regimen

for true anestrous cases would constitute insertion of a

progesterone device for 7–9 days, removal of the device, and insemination at detected estrus.

The insertion of a progesterone-releasing intravaginal device (PRID; 1.55 g progesterone) for 7 days and its removal at the end of that period induced cyclicity in 64 of 90 (71%) of treated cows in contrast to only 33 of 83 (40%) of untreated controls.

cyclicity was confirmed by the presence of a CL at ovarian ultrasonography 11 days after PRID removal.

For therapy of anestrus at herd level, a 7-day treatment followed by PGF2α injection at device removal is often recommended to ensure luteolysis in cows that were “silent ovulators” (sub-estrus) and in those that were falsely categorized as anestrous due to poor estrus detection efficiency (unobserved estrus).

The two brands of intravaginal progesterone devices

CIDR® and PRID®

Estradiol

Estradiol alone may be used for inducing estrus in anestrous

cattle, but it is not recommended because the ovulatory

response to estradiol is often variable.

the use of a CIDR device for 6 days, followed by an injection of

1 mg estradiol benzoate 24 hours after CIDR removal

resulted in 87% of dairy cows being detected in estrus within

7 days of estradiol treatment; 79% of cows detected in estrus

ovulated and a conception rate of 42% was attained

GnRH

Exogenous administration of GnRH induces LH release as

early as the first week after calving in dairy cows, although

the response is significantly higher by the second week

If a dominant LH-responsive follicle is present

at the time of GnRH injection, there is a high probability

of it ovulating, especially when the follicle has not

been exposed to progesterone.

In our laboratory, four of five lactating dairy cows given 100 μg GnRH in the second week after calving, ovulated (R. Salehi, M. Colazo and D. Ambrose, unpublished data, 2013).

 Inducing an ovulation in anestrous cows with no prior exposure to progesterone could result in short luteal phases, increasing the chances for cows to revert back into anestrus.

 In one study,82 93 of 108 (86%) anestrous cows ovulated in response to a GnRH injection, but 20% of these cows reverted to anestrus. Thus, although GnRH can be used independently to induce ovulations in anestrous dairy cows,

one must recognize that short luteal phases and reversion to anestrus are drawbacks associated with this approach.

Using GnRH in combination with PGF2α in a protocol

such as Ovsynch  followed by timed insemination has been

effective in the management of anestrous cows.

Although the conception rates in anestrous cows following this

approach are generally lower than in cyclic controls, several

studies have reported acceptable conception rates after timed AI,

using porcine LH can be used in lieu of GnRH in the Ovsynch

protocol but these products are significantly more expensive

than GnRH. Furthermore, there is limited research on the

use of these products in the management of anestrous cattle.

In one study,98 replacing the second GnRH injection of the

Ovsynch protocol with a commercial preparation of porcine

LH, in predominantly cyclic lactating dairy cows,

significantly improved pregnancy per AI by 14 percentile

points (42% vs. 28%; n = 308). In the same study, when

porcine LH was used in lieu of the first GnRH injection of

the Ovsynch protocol, on a different subset of cows, the

ovulatory response to porcine LH treatment was significantly

higher than to GnRH treatment (62% vs. 44%). Since several

studies have reported that cows ovulating in response to the

first GnRH treatment of the Ovsynch protocol have higher

pregnancy rates after timed AI,79,83,99 using porcine LH in the

treatment of individual cases of anestrus has potential value.

In this regard, pregnancy per AI was greatly enhanced in

anestrous cows that ovulated in response to the first GnRH

treatment of the Ovsynch protocol (46% vs. 6%) than in

anestrous cows that failed to ovulate.99 These results strongly

indicate that determining the ovulation response to the first

GnRH treatment in anestrous cows, by ultrasonography,

would have significant value in predicting the probability of

pregnancy.

Combined use of progesterone, GnRH, and PGF2α

The incorporation of an intravaginal progesterone device

into a synchronized ovulation program such as Ovsynch is

one approach to improve treatment outcomes (pregnancy)

in anestrous cows.

A second approach is to use either progesterone, GnRH and PGF2α, or PGF2α alone, as a presynchronization treatment before the initiation of the Ovsynch protocol.us cows subjected to Ovsynch

plus timed AI, with the insertion of a proge

Studies show that anestrosterone device for

the first 7 days of the protocol, have higher pregnancy per AI

than that of anestrous cows subjected to the same protocol

without progesterone.

Pregnancies per AI are comparable to that of cyclic cows subjected to Ovsynch plus timed AI wit no progesterone treatment .

A large field trial (12 herds, 1662 cows) conducted in New Zealand on anestrous dairy cows concluded that therapeutic intervention is the most economic option compared with no treatment, and that including an intravaginal progesterone device in the Ovsynch protocol was most cost-effective, attaining the highest net benefit of NZ$80.40 per cow.

 The Ovsynch/timed AI protocol has been used successfully in cows with cystic

ovarian follicles,44 although the addition of a progesterone

device to this protocol did not improve pregnancy.104 Ovarian

responses documented by ultrasonography