estrous synchronization in sheep and goat

7/16/2019 estrous synchronization in sheep and goat

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1

Estrus synchronization inSheep and Goat

ByDr. T.C.Jangir (2012V22M)

MAJORCREDIT SEMINAR

ON


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DEFINITIOS:-

ESTRUS: Period of sexual receptivity.

Commonly referred to as Heat

ESTROUS CYCLE: Reproductive cycle of female,

generally defined as period from one estrus to the

next.

ESTROUS CYCLE


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ESTROUS CYCLE

Seasonally polyestrus:

Cycles occur only during certain times of the year

Long-day breeders:

Cycle when day length increases

Ex: mare

Short-day breeders:

Begin to cycle as day length decreases

Ex: sheep, goats


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Reproductive parameters of sheep and goat (Jainudeen, et al.

Reproduction in farm animals 7th edition)

Particular sheep goat

Length of estrous cycle

(days)

17

(14-19)

21 (also short cycles)

(18-22)

Duration of estrous (hrs) 24-36 24-48

Time of ovulation 30-36 hrs from begning

of estrous

21-36 hrs from begning

of estrous


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Considerations for Small Ruminants

seasonal breeding patterns

lack of large-scale application of AI.

In sheep, AI is further impaired by problems in freezing

ram semen and problems in the transcervical deposition

of semen.


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Endocrine changes during the

oestrous cycle


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7


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8


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Trends in harmone concentrations in the peripheral

circulation of the ewe during the oestrous cycle (DavidNoakes ,Veterinary Reproduction and Obstetrics 9th edition)

FSH (ng/ml)

LH (ng/ml)

Estrogens (pg/ml)

Progestrone

(ng/ml)


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Endocrine changes during the oestrous cycle

in ewe-

Just before the onset of oestrus rise in oestrogens in the

peripheral circulation, particularly oestradiol-17.

This is followed by a sudden surge of LH which reaches a peakabout 14 hours before ovulation; coincidental with this peak is

a rise in FSH.

There is also a second FSH peak 2 days after ovulation.

Prolactin fluctuates throughout the oestrous cycle.


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Trends in harmone concentrations in the

peripheral circulation of the goat during theoestrous cycle


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Behavioral signs of estrus

Does

Bleating continuously

Swollen red colored vulva

Flagging of the tail

Frequent urination

Cervical mucus discharge, which causes hairs to stick

together

Restlessness

Mounting other goats andseeking the buck


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Behavioral signs of estrus

Ewes

The signs of estrus in the ewe are not obvious unless a

ram is present.

As in the doe, the vulva is swollen and redder than usual,and there is a discharge of mucus but is difficult to see in

a ewe with a tail or fleece.

Normal duration will be 24 to 36 hours.


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Ram has found ewe on heat. She stands still, looking around

at the ram, tail fanning, ears pricked. She is waiting to be

mounted.


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Ram 'sniff hunting' ewes


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Estrus detection techniques

Using a teaser ram or buck

Tying an apron made of leather or canvas around thebody of a ram or buck.

Using a teaser with a marking harness


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Estrus synchronization

Manipulation of the estrous cycle to bring a large

proportion of females in estrus at a pre-determined

time.


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Introduction

Estrus synchronization (ES) in livestock focuses on themanipulation of either the luteal or the follicular phase

of the estrous cycle.

In does and ewes, the opportunity for control is greaterduring the luteal phase, which is of longer duration and

more responsive to manipulation.

Strategies can be employed to extend the luteal phase by

supplying exogenous progesterone or to shorten this

phase by prematurely regressing existing CL.


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Why do we need to synchronize estrus?

To facilitate the practice of artificial insemination, eitherfor genetic improvement or to reduce the number oframs/bucks needed to be kept.

To match the period of lambing/kidding with feedavailability or to produce products out-of-season.

Used as an initial step for super-ovulation and

subsequent embryo transfer.

Induction of estrus in ewes/does with silent estrus toshorten the lambing/kidding interval.


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Disadvantages of synchronized

ovulation

Low conception rates

Cost

Concentrated labor required during breeding and

calving season

E S h i i


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Estrous SynchronizationMethods

A. Hormonal :

Shortening the luteal phase

PGF2Estrogen

Extending the luteal phase

Long term use of progestrone or progestogen (14-21 days)

B. Non-hormonal :Light,

nutrition,

weaning,

male stimulation


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Compounds used in estrous

synchronization1. Progesterone

It controls the life of thecorpus luteum ormanipulate circulatingprogesteroneconcentrations thatallows regulation ofoestrus and ovulation(Hansel and Convey,1983).


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The progesterone or progestagen treatment can be

delivered through-

intravaginal sponge,

CIDR, PRID or

a subcutaneous implant

(Evans and Maxwell, 1987; Ritar et

al., 1989; Freitas et al., 1997).


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2. Synthetic progestogens

Norgestomet Crestar(implant)

Medroxy acetate

progesterone (MAP)

Melengestrol acetate

(MGA) (oral)

flurogestone acetate (FGA)


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Steps in CIDR application/loading


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CIDR application/loading


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Intravaginal Sponges

Intravaginal sponges have

been the traditional

treatment of choice for ES

in small ruminants, during

the breeding and anestrusseasons. They are

impregnated with -

A. progestagens or

B. natural progesterone


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Cont

In sheep, progestagen

impregnated intravaginal

sponges or CIDRs are

inserted intravaginally for

1214 days. Ewes show oestrus

approximately 48 h after

device removal.


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In goats, progestagen

impregnated sponges are

inserted intravaginally for 1618 days, whilst CIDRs are left

in place for 1821 days.

The majority of does will bein oestrus approximately 48 h

after removal (Wheaton et al.,

1993).

At the time of removal,

animals are administered

eCG/PMSG.

Intra-vag na sponges or estrus n uct on


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Intra-vag na sponges or estrus n uct on

and synchronization (prepaired at CSWRI)

Developed indigenously for

estrus induction and

synchronization in sheep

and goats.

A solution of progesterone

(0.175 g/ml) was prepared

in ethanol and each sponge

was loaded with 2 mlsolution.


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Intra-vaginal sponges for estrus induction

and synchronization (CSWRI) Protocol


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prostaglandin or its analogue

The primary luteolytic factor in ruminants is the

prostaglandin F2 ( McCracken et al., 1972); thus,

administration of exogenous PGF2 or its analogues

is useful for inducing luteolysis (Douglas andGinther, 1973).

The main advantage of prostaglandin treatment is

the possibility of administration by intramuscular

injection.


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ProstaglandinsIntramuscular injection requires higher dosage than

intrauterine injection because of the short half-life ofthe substance.

Half-life about 2-3 minutes; approximately 90%deactivated in single passage through body.


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The inconveniences of using


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The inconveniences of using

PGF2 are-

1.The CL can be responsive to PGF2 from day 3 of the

oestrous cycle (Rubianes et al.,2003) to the day of natural

luteolysis; therefore, animals should contain an active CL.

2. The second inconvenience is that the 910-day protocol is

effective in synchronising oestrus, but fertility of the ewes at

first mating is only about 70%, significantly lower than that

after progestagen treatments and natural services (Boland et

al., 1978; Godfrey et al., 1999).


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A protocol developed for synchronization of estrus in

cycling native ewes at CSWRI includes administration of

two intramuscular injections of PGF2 7.5 mg at 10 days

interval.


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GnRH agonists Hypothalamus hormone

Release of FSH, LH

Buselerin (Cystorelin, Factrel, Fertagyl,

OvaCyst, Receptal etc.)


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Estrogens Estradiol conjugates

Estradiol valerate

Estradiol bazoate

Estradiol cypionateGonadotropins

eCG or PMSG

FSHhCG


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Melatonin and Photoperiodicity

Discovered by Lerner et al. (1958).

Photoperiodic information is received at the level of the

retina and transmitted, via a multi-step neural pathway, tothe pineal gland, where the message modulates the

rhythm of melatonin secretion (Bittman et al., 1983).


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Diagram on the role of photoperiod and pineal gland onsteroid feedback and seasonal estrous cycles.


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Cont It has been reported that in anoestrous ewes a

significant increase of GnRH secretion after 40 days andhigh GnRH and LH pulsatility occurs after 74 days of

melatonin treatment (Vigui et al., 1995).

And it is done by reducing tyrosine hydroxylase activity and,therefore, the secretion of dopamine in the median

eminence (Vigui et al., 1997).

Thereby, implants cause a short day-like response bylengthening the duration of the melatonin signal (Malpaux

et al., 1997).


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Cont

The implants contain 18 mg of melatonin and are

designed to maintain high plasma melatonin

concentrations for at least 60 days, although most of

them continue releasing the hormone for over 100 days

(Forcada et al., 2002).

The implant release maintains daytime plasma

concentrations of melatonin >100 pg/mL, in both ewes

(Forcada et al., 1995) and goats (Delgadillo et al., 2001).

The male effect


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The male effect

The male can be used to stimulate estrus activity of

females that have been previously isolated from males

for a period of 34 weeks.

The so-called male effect is a technique to stimulate thesexual activity in seasonally anovulatory goats ( Pellicer-

Rubio et al., 2007).

After the period of separation, the male animal is

suddenly introduced to the group of females.


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In response to introduction of the male, ewes/does secrete

increasing amounts of LH and FSH, which result in ovulationafter 2 or 3 days of male introduction.

In cyclic goats, highest frequency of estrus was observed

within the first 3 days of buck introduction.


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The following factors affect response to male

introduction:

High sexual activity or libido test scores of male

High plane of nutrition of female

The longer lambs/kids have been weaned from ewes/does,

the better the response of the ewes/does.


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estrous synchronization in sheep and goat

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