Estrus Synchronization in Cows
Synchronization means to happen at the same time or to move at same speed. Synchronization of estrus causes the herd to come in estrus almost at the same time.
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| Methods of Estrus Synchronization in Cows |
Applications:
It is used for reproductive management of herd at individual level or at herd level.
For induction of parturition at the same time we also synchronize. All animals parturate at same time with difference of 1-2 days.
Preparation of animal for competition. For example for milk production we prepare animal for specific period of time by synchronization.
Help in breeding program specially beef production program.
Methods of Synchronization
There are two methods:
o Hormonal method
o Non hormonal method
Non Hormonal
If you are going to use non hormonal method then it should be done 20-30 days prior to commencement of breeding season. It includes the techniques as:
Introduction of Male in a Herd:
If you enter male one month prior to breeding season then all females will show heat. It is due to pheromones secreted in urine, feaces, sweat and saliva of male. These are chemicals and act as hormones. By smelling theses females are affected.
Provision of Artificial Light:
Particularly it works in the mare. The mare is a long day breeder. It requires extra light. We provide 15- 16 hours extra light per day for the onset of heat.
Nutrition:
By improving nutrition we may get help.
Hormonal Methods
There are three types of hormones used:
o Prostaglandins
o Progesterone
o Gonadotropin releasing hormone
They may be used as single or in combination
Prostaglandins:
Synthetic or natural preparations of prostaglandins are available
Prostaglandin hormone works in cyclic animals having CL on the ovary. It will cause the lysis of CL, progesterone level will go down, feedback mechanism stimulates anterior pituitary and FSH will be secreted. In case of plain ovary use other hormones.
Prostaglandin and progesterone can be given in combination. Give progesterone for 10-15 days and then sudden drop in it and give prostaglandin.
Cloprostenol is synthetic analogue of PGF2α. It can be used through intramuscular, intravenous, intrauterine or direct injection in CL (using specific needle and syringe). 2 ml is dose for intramuscular rout, 1 ml for intrauterine (1 ml + 9 ml of dextrose solution or normal saline), and 0.5 ml for CL.
Programs for Synchronization with PGF2α:
There are 4 programs for synchronization on herd level. At individual level go for rectal palpation, judge CL, if persistent then give PG to make animal to come in heat. Response time for PG is within 48-120 hours and average 72 hours. One must be careful after injection; within 5 days animal shows heat.
Program A
Single injection with 5 day breeding program
o You will palpate all the animals, confirmation of CL
o Injection of PGF2α (natural 2 cc and synthetic 4-5 cc)
o Confirmation of estrous
o AI (12 hours after standing estrus).
Program B
Single injection with 10 day breeding program
o Should be implemented at the starts of breeding season
o In first 5 days of breeding season animals show the natural estrus; they will be inseminated.
o Animals not showing estrus in first 5 days will not be inseminated and they are given single injection of PGF2α.
o Confirmation of estrus
o AI (12 hours after standing estrus).
Program C:
Double injection with 10 day breeding program
o Inject PGF2α on day 1 to all animals
o For next 5 days detection of estrus and proper insemination
o PGF2α (second injection) to those which did not show estrus in first 5 days
o In next 5 days detection of estrus and proper insemination
Program D:
2 injections within 5 day program
o PGF2α injection to all animals in herd to be synchronized and then do not go for detection of estrus in next 5 days and without A.I give second injection to animal at the interval of 11-14 days (14 days preferred) from the first injection
o Detection of estrous and confirmation within 5 days of second injection and AI
o Accuracy of this program is above 80 %. It is mostly used. It is the best method
Key Points:
o The animal should be shifted to high plan of nutrition before going for synchronization.
o One can go for synchronization after 40-50 days of calving.
o There should be accurate estrus detection method.
o Herd should be cyclic one (key point for PGF2α)
o Be careful upto 120 hours after giving injection.
Limitations for Use of PGF2α:
o Can be used only in cyclic animals
o Not effective one in proestrus or immediate metestrus
o Not effective upto 7 days post estrus
Progesterone:
Other major hormone which can be used is progesterone. It should be used 15-20 days before the onset of breeding season.
With progesterone basic principle is; first you have to maintain luteal activity of animal. You have to continue this for 10-12 days and after 10-12 days suddenly remove the source of progesterone. Due to sudden removal there will be negative feedback, anterior pituitary will be stimulated and there will be release of FSH. Possibility of estrus is 5-7 days after the removal of source. This can be used by intramuscular, subcutaneous, oral, or intravaginal routes.
Oral dose is 0.5 mg/herd/day. Mix the drugs with vegetable oil and that oil is mixed in concentrate and given for 10 days. When you stop; within next 5-7 days following animal will show estrus.
Intravaginal: Progesterone Releasing Intravaginal Device (PRID) and Control Internal Drug Releasing (CIDR) placed in vagina. Take care of urination. Special speculum is used. Place near cervix. Gel is used to lubricate sponge, oil is not used. Lubricate it from side. Keep it for 7-10 days. Each time sterilize speculum when speculum is used in large number of animals. Never use oral preparation for lubrication.
Hormones ECG and PMSG are used for induction of estrus. After removal of sponge you give ECG 300-400 IU through I/M in animal that increases the fecundity rate.
GnRH:
It is for induction of estrus. Gonadotropin and gonadotropin like hormones stimulate the release of FSH and LH. ECG, PMSG are gonadotropin like hormones.
Estrogen:
Estrogen is not good choice for synchronization. This is for estrus induction. It does not help in formation of follicle. It only stimulates epithelium of the reproductive system. High dose may produce the behavioral signs and some mucous. If ovary has mature follicle then it may help in ovulation.
It is used for induction of estrus but still not good choice.
10-20 mg (1-2 cc of stilbestrol) I/M
This is given in combination with progesterone or dexamethasone for induction of parturition.