Estrous Synchronization in Farm Animals
Dr. SANJAY K. MISHRA
Veterinary Medical Officer, Animal Husbandry Department U.P.
Ex-Assistant professor, Gynaecology and obstetrics, C.V.Sc. & A.H., DUVASU, Mathura, U.P. India
Definition: A managemental technique that enables use of hormones/non-hormones to reschedule or control the estrous cycle
Hormones associated with reproduction
LH & FSH Progesterone Estrogen Prostaglandin Melatonin
Objectives of Synchronization :
Shorten calving season.
– To synchronize large group to ovulate at same time
.-Reduce labor required for AI breeding.-
Market uniform calf crop (same age)
.- To provide a specific quantity of milk per day to society.
– Improving management (fodder and skilled technical assistance)ü and thereby optimizing feeding and management practices.
– For advancing the breeding season especially in seasonal breeders (sheep, goat, mare and cat).
-For management of postpartum (unovulatory) and silent estrus
.- Important component for embryo transfer technology (ETT).
– Management of breeding and calving schedule. Through Estrous Synchronization.
Characteristics of Animal Undergoing Estrus Synchronization;
– Should be in good plane of nutrition and managementØ practices
– Body condition score should be ≥3.0
Ø There should be no history of abnormal discharge and breeding problem
– Semen used for AI should be of good quality
Ø Animal should have calve before 45 days.
Basis for Synchronization of Estrus ;
Manipulate life span of CL.- Manipulate growth of follicles and timing of ovulation
Shortening the luteal phase – Luteolysis • PGF2 a• Estrogen
Extending the luteal phase– Negative feedback on LH • Long term use of progesterone or progestagen for 14-21 days
Synchronization Methods;
Hormonal Methods ; PGF2α, GnRH, E2, P4
Non Hormonal ;
- Steaming up, light, Weaning, Ram effect
Immunization (GnRH, Inhibin, Androsteindione)
Hormonal Techniques
A)Prostaglandins – Principle of PGF2aUse
Regress active corpus luteum
– Only effective on a day 5 – 17 of estrous cycle
– Not effective on days 1 – 4 (CL not responsive)ü 18 – 21 (CL already regressed)
Induction of Ovulation with PGF2a
Works on CL. And ovulation time dependent on status of follicular wave
B) GnRH; Principle of GnRH Use
– Luteinize or Ovulate a dominant follicle and terminates the current follicular wave;. Inhibin and Estradiol decrease. FSH increases to “recruit” a new follicular wave.
– No effect on old CL if present
– A dominant follicle must be present to regress newly formed CL or– old CL . — Generally followed by PGF2a
C) Progestagens ; Principle of Progestagen Use
— Provides progesterone simulates a CL and Prevents ovulation. Has no effect on the animal’s CL (i.e. normal lifespan)ü does not regress the CL! and remove after animal’s CL regresses
. – Current or next follicular wave will ovulate that occurs 2 – 5 days latter’ – May use PGF2a to regress animal’s CL
Different Progestagen Preparations; – Injection -Feed (MGA) – Ear Implant – Control Internal Drug Release (CIDR) – Progesterone Releasing Intra Vaginal Device (PRID)
Summary of Hormones Used in Estrous Synchronization;
GnRH• The random administration of GnRH during the estrous cycle results in LH release, causes ovulation or luteinization of large follicles present in the ovary, synchronizes the recruitment of a new follicular wave
PGF2α; Prostaglandin synchronize estrus by inducing the regression of the corpus luteum .Usually given in the diestrous phase of estrous cycle when the CL is well developed .The stage of follicular wave development at the time of PGF2α treatment appears to be the factor determining the time of estrus onset
E2• Induce a preovulatory-like LH surge, ovulation and luteolytic activity during the luteal phase
P4 ; Progesterone is released slowly from a device that was inserted into the vagina for 5-7 or more days and after withdrawl of the device there will be a sudden release of GnRH causing resumption of estrus
Synchronization methods: drug trade names and effectiveness
| Method | Trade name | Female “type” for drug effectiveness |
| Prostaglandins | Lutalyse* Estrumate* Equimate∞ * | Cycling cows or heifers
∞Cycling mares |
| Progestins | MGA* CIDR*
Regumate∞ |
*Cycling cows or heifers *Anestrous cows or heifers
∞Mares |
| Gonadotropin Releasing Hormones | Cystorelin*
Ovuplant∞ * |
Postpartum cows *Anestrous cows
∞Cycling mares |
| Placental Gonadotropins | PG600^ | ^Peri-pubertal gilts
|
Different Synchronization Protocols
One Injection of PG cost Rs. 200/head (Approx.)
Advantages – Useful for detection of estrus in heifers and cows ,decreased drug cost and limited animal handling
Limitations – 10-25% of females may not be detected in estrus during days 0 to 10.Poor degree of synchrony on females that return to estrus . Must have CL .Length of estrus detection .Abortion
Two Injection of PG with split insemination cost Rs. 400/head (Approx.)
Advantages – Useful for detection of estrus in heifers and cows with tighter synchrony than one injection method . Can use fixed insemination time after 2 nd injection
Limitations – Females must have functional CL. Length of estrus detection .
Administration of PGF will cause abortion in pregnant animals
Protocol for synchronizing heifers using FGA and PGF;
Advantages – Proven system for heifers . Inexpensive method .
Can hasten cyclicity in anestrous females
Limitations – Length of program. Must have appropriate feeding space to allow efficient consumption. Estrus synchronization may be variable. Must ensure uniform daily consumption of feed supplement prior to and during oral administration of MGA . cost Rs. 800/head (Approx.)
CIDR protocol; Cost Rs. 1400-1500/head (Approx.)
Advantages – Useful for detection of estrus in heifers and cows It induces cyclicity in a percentage of anestrous cattle leads to High pregnancy rate
Limitations – Possible retention failure of CIDR and Cost per treatment may be higher than other methods . An additional day of processing for hormone treatment would be required to facilitate fixed time A.I.
Ovsynch /GnRH – PG -GnRH ; Cost Rs. 1400-1500/head (Approx.)
Advantages – Higher and tighter estrus synchrony compared to PGF protocols .
Allows for estrus detection or timed AI
Limitations – Higher cost due to hormone injections and increase time and labor thus not recommended for use in heifers
Ovsynch Problems; Works best on animals that are near day 7 of the cycle at 1stGnRH
Disadvantages of Synchronization;
Low conception rates and higher cost.Concentrated labor required during breeding and calving season. All cows calving at once (especially bad if high- incidence of dystocia occur)
Synchronization in the Mare
Hormonal Methods :- Prostaglandin: When administered in diestrus, expect ovulation in 7-12 days .Mare CL more sensitive than cow’s only effective in season
hCG – ovulation induction,Ø >35 mm follicle
ProgestinsØ Altrenogest (Regumate) but only effective in season.Reduce estrus behavior in racing animals
Non Hormonal Methods : Light – 16 hrs day light for 60 – 90 days.
Synchronization in the Sow Hormonal Methods :
Prostaglandin :Ø Only effective days 12 – 17 Prostaglandin will not cause CL regression until day 12 of cycle because LH binds to luteal cell receptor with strong affinity following ovulation and is not released until day 12. Repeated injections over two to three days will regress CL sooner, but is not practical.
Progestins – Common progestins will synchronize estrus but cause ovarian cysts – Regumate (oral) for 18 days: Regumate has been found to be effective .
Noncycling gilts can be synchronized with P.G. 600 (400 IU eCG and 200 IU hCG)
Non Hormonal Methods :- Weaning
Synchronization in Sheep & Goats Hormonal Methods :
Most common protocols use either prostaglandins or PRID/CIDR Progestin
CIDR/ Vaginal Sponges – works alone during breeding season but out of breeding season – requires eCG
Prostaglandin – Works only during breeding season
Non Hormonal Methods : Lights – decrease day length .
Melatonin given orally or implants.
Non-Hormonal Methods:
In spite of the advantages associated with hormonal synchronization.
Drawbacks : Disturbance in the luteinizing hormone (LH) secretion patterns.Altered follicular dynamics.Production of eCG antibodies. Impaired sperm motility inside the female reproductive tract and decrease sexual attractiveness in ewes
Ram Effect Photoperiod 3. Flushing Up 4. Weaning
Ram Effect
- Isolation of ram before the starting of normal breeding season
- Introduction of ram to ewe inducing ovulation
Central Nervous System, Ram stimuli (Pheromones) leads to olfactory sense –Hypothalamus-GnRH- Pituitary gland –FSH, LH – Ovary -Reproductive tract
Photoperiod Management –Controlled photoperiod- LD (16h/d)– SD (8h/d)
Flushing – up :
The practice of increasing nutrient intake and condition prior to and during breeding is called flushing. Its purpose is to increase the rate of ovulation and, hence, lambing rate. Flushing is especially beneficial for thin ewes that have not recovered from previous lactation stress. High plane of nutrition promotes a greater production of insulin which increases the uptake of glucose leads to increase in the growth of oocytes. The long term protein flushing increased the number of small and medium follicles and follicular waves, the size of ovulatory follicles in the first and second estrus.
Immunization Method;
Anti GnRH • Anti Androstenedione • Anti Inhibin
- Anti GnRH – Immunocastration in males (reducing aggressive behaviour and preventing the development of secondary sex characters) . Used in females by suppressing cyclical ovarian activity.
- Anti Androstenedione – Increased lambing rates have been obtained by the use of an immunogen, produced by conjugating a derivative of the natural ovarian hormone androstenedione with human serum albumen.
- Anti Inhibin – Used to increase the ovulation rate in cattle and sheep experimentally.
Important Consideration for Estrus Synchronization:
Estrus synchronization is never a substitute for nutrition, herd health and proper management.
Estrus synchronization should not be used as a crutch for poor management. When administered appropriately, estrus synchronization is an effective reproductive management tool that can be used to facilitate AI.
Proper selection of females before beginning estrus synchronization by using data such as age, body weight, BCS, RTS etc.
Estrus synchronization definitely show results as earlier calving season.More time to return to Estrus.
Increased opportunity to become pregnant however, due to expense and labor intensity this is not for everyone.
