Conventional method of oestrus synchronization in sheep

Conventional method of Oestrus synchronization in sheep

EIAR-DBARC-ICARDA-ILRI (LIVES)-FAO Training on Reproduction in

Sheep and Goat, Debre Berhan, Ethiopia, 13-15 October 2014

Zeleke Mekuriaw

Outline

Introduction

Merits of oestrus synchronization

Principles of oestrus synchronization

Methods of oestrus synchronization

• Exogenous Progesterones/progestagens

o Routs of administration

• Prostaglandins /analogues

• Natural Method 2

Introduction

• Naturally, mating occurs when female is receptive regardless of herdsman’s

willingness.

• Artificial manipulation is important to the advantage of increasing the

efficiency and profitability of the farm.

• One of the artificial manipulation techniques is oestrus synchronization.

3

Introduction…

Oestrus synchronization:

• Artificial induction of heat in females simultaneously

• Labour and time management tool

• A breeding tool

4

Merits of oestrus synchronization

• Reduces time and labour for heat detection

• Improves accuracy of heat detection

• Facilitates application of fixed time AI

• Facilitates MOET

5

Merits of oestrus synchronization…

• Enables programed mating

• Enables programed lambing (targeting feed availability, market, health)

• Induces ovarian activity in anoestrus ewes & pre-pubertal ewe lambs

• Age uniformity in lambs (fore selling, feeding & healthcare)

• Physiological similarity of ewes (for feeding management)

6

Methods of oestrous synchronization in ewes

Various synchronization agents available

The choice depends on:

– effectiveness in regulating ovarian activity

– Precision of the control (compactness)

– Fertility from induced oestrus

– Ease of administration

– Absence of undesirable side effects

– Cost effectiveness 7

Principles of oestrus synchronization

1. Shortening life span of CL-PGF2ɚ/analogue

2. Prolonging luteal phase-Progesterone/progestagen

8

Comparison of prostaglandin & progesterone based synchronization

Progesterone/its analogue

Prostaglandin/its analogue

Advantage Induces cyclicity Cheaper

More compact synchrony Easy to apply

Does not induce abortion Treat luteal cyst

Limitations Expensive Effective only in cycling cows

Complicated application procedures

Effective from 4 to 14 days of estrous cycle (matured CL)

Induces abortion if pregnant ewe is injected by mistake

Less compact synchrony

9

Use of Exogenous Progesterone/Progestagens

– Exogenous progesterone/progestagens extend luteal phase

– the CL regresses naturally during the period when

exogenous source is applied.

– The exogenous source continues to exert a negative

feedback on FSH and LH secretion, even after CL regression.

– When external source is later withdrawn, follicular growth

starts simultaneously in all treated females.

10

Routes of administration of progesterone/progestagens

• Oral administration

• skin implants

• Intravaginal treatments

11

The oral administration

– Melengestrol acetate (MGA), an orally active synthetic progestagen

– twice daily feeding of 0.125 mg MGA for an 8-day period could induce

an out-of-season synchronized oestrus in ewes.

Drawbacks:

– time and labour costs involved in oral dosing

– difficulty to achieve a smooth and steady input of progestagen

– Less practical due to lack of sharp and predictable result

Implant treatments

– Subcutaneous implant of he potent progestagen,

norgestmet used.

– About 1cm implant contains 1.2 or 3mg of norgestmet is

inserted for 12 days.

– Mean time of onset of oestrus after removal of implant is

26 to 30 hrs

Intravaginal administration

 The treatment of choice for oestrus synchronization in sheep

(in all seasons).

• Progestagen impregnated sponges used

• Inserted over periods of 12 to14 days

• Used in conjunction with PMSG

Intravaginal administration …

• FGA (Fluorogestone acetate)

– marketed as Chronogest®

or Cronolone®. (45 mg),

– widely used either in

conjunction with PMSG,

FSH or PGF2ɚ

Intravaginal administration…

• MAP (medroxyprogesterone acetate )

– 6-methyl-17-acetoxyprogesterone

– marketed as Veramix (Pharmacia & Upjohn, Orangeville,

Canada)

– Contain 60 mg of the progesterone analogue

– The same effect as FGA

Intravaginal administration…

• CIDR (Controlled Internal Drug Releasing)

– dispenser developed in New

Zealand.

– constructed from a natural

progesterone impregnated

medical silicone elastomer.

Intravaginal administration…

Merits and demerits of CIDR device

Merits

– natural progesterone

– aesthetically more pleasant to handle

Demerits

– higher incidence of loss (13.5%) compared to sponges (6.7%)

– more expensive than the progestagen sponges

Use of Prostaglandins / their analogues

• The administration of PGF2ɚ causes

regression of the CL

• Possible only from day 4 to 14 of the cycle

• No response to PGF2 administration

during the refractory period (0-4th & 14th-

16th day of oestrous cycle)

• The technique only suitable during the

breeding season

• Onset of oestrus 36-48hrs after injection

Natural Method of synchronization

Male effect:

– sudden exposure to rams

– The duration of exposure (6 days for goats, 15days for sheep)

– isolation period (at east 3 wks)

– distance of isolation (100-500m)

Photoperiod:

– manipulating the light environment

combination of the two -photoperiod and male effect

Natural Method of synchronization…

Merits :

– relatively cheaper

– More consumer preference/“hormone-free” animal

products.

Demerits:

– variability in the onset of oestrus

– requires insemination at the observed heat

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