Presented by Zeleke Mekuriaw at the EIAR-DBARC-ICARDA-ILRI (LIVES)-FAO Training Workshop on Reproduction in Sheep and Goat, Debre Berhan, Ethiopia, 13-15 October 2014

1. Conventional method of Oestrus synchronization in sheep
Zeleke Mekuriaw
EIAR-DBARC-ICARDA-ILRI (LIVES)-FAO Training on Reproduction in
Sheep and Goat, Debre Berhan, Ethiopia, 13-15 October 2014

2. 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

3. 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

4. Introduction…
 Oestrus synchronization:
• Artificial induction of heat in females simultaneously
• Labour and time management tool
• A breeding tool
4

5. 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

6. 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

7. 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

8. Principles of oestrus synchronization
1. Shortening life span of CL-PGF2ɚ/
analogue
2. Prolonging luteal phase-
Progesterone/progestagen
8

9. 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

10. 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

11. Routes of administration of progesterone/progestagens
• Oral administration
• skin implants
• Intravaginal treatments
11

12. 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

13. 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

14. 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

15. Intravaginal administration …
• FGA (Fluorogestone acetate)
– marketed as Chronogest®
or Cronolone®. (45 mg),
– widely used either in
conjunction with PMSG,
FSH or PGF2ɚ

16. 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

17. Intravaginal administration…
• CIDR (Controlled Internal
Drug Releasing)
– dispenser developed in New
Zealand.
– constructed from a natural
progesterone impregnated
medical silicone elastomer.

18. 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

19. 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

20. 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

21. 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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