ESTRUS INDUCTION & SYNCHRONIZATION PROTOCOLS IN DAIRY CATTLE

Failures to resume cyclicity after calving and silent oestrus are the two most serious

problems that affect reproductive efciency in dairy cattle. To achieve the target of a calf

per year in dairy cattle , it is essential that estrus is detected at the earliest post-calving and insemination is made at the end of the voluntary waiting period of 45-60 day. Detection of estrus is necessary for a planned insemination program for dairy cattle and is the key to the successful use of articial insemination (Al).

As a short term strategies hormonal treatment are preferred to induce cyclicity or bringing them in heat within a narrow window. There are several hormonal preparations commonly used to induce estrus in cyclic as well as acyclic dairy cattle . These include administration of prostaglandin, progesterone, gonadotrophins and gonadotrophin releasing hormone or their synthetic analogues, either alone or in various combinations. Numbers of estrus synchronization programmes are available in cattle based on the use of various hormones like progesterone, prostaglandin F2a and their various combinations with other hormones like estrogen and Gonadotrophin Releasing hormone (GnRH). Selection of appropriate estrus synchronization protocol should be made on the basis of management capabilities and expectations of the farmer. Synchronization of oestrus can be accomplished with the injection of prostaglandin F2a alone, but it needs proper detection of the ovarian status of the cows as prostaglandin F2a is active in only functional corpus luteum in between 8 to 17 days of estrous cycle. Progesterone may reduce fertility up to 14 percent, but short time progesterone exposure (less than 14 days) is beneficial. Addition of GnRH in the Progesterone or Prostaglandin based synchronization programme is helpful for more synchrony in estrus as GnRH may be helpful to synchronize the oestrous cycle in delayed pubertal heifers and post partum cows (Post partum anoestrum) and further a single, timed artificial insemination is possible with this method. New methods of synchronizing estrus in which the GnRH-PG protocol is preceded by progesterone treatment offer effective synchronization of estrus with high fertility.

Some of the commonly available hormonal preparations are as follows.

Gland Hormones Ingredients in

commercial preparation Commercial

Product Packing

Hypothalamus GnRH Buserelin 4mcg/ml Receptal, MSD 2.5 ml, 10 ml

Buserelin 4mcg/ml Gynarich, Intas 2.5 ml, 5 ml

Buserelin 4mcg/ml Pregulate, Virbac 5 ml

Pituitary hCG Chorionic gonadotrophin Chorulon, MSD 1500 IU Vial

Pituitary FSH Follicle stimulating

hormone Folltropin V,

Bioniche 400 mg

Mostly used for

superovulation

Uterus PMSG Pregnant mare serum

gonadotrophin Folligon, MSD 1000 IU vial

Uterus Prostaglandin Dinoprost tromethamine

5 mg/ml Lutalyse, Pzer 5 ml, 10 ml

Cloprostenol 250 mcg /ml Estrumate, MSD 2 ml

Cloprostenol 250 mcg /ml Pregova, Virbac 2 ml

Cloprostenol 250 mcg /ml Vetmate, Vetcare 2 ml

Cloprostenol 250 mcg /ml Pragma, Intas 2 ml

Luprostiol 7.5 mg/ml Prosolvin, MSD 2 ml, 10 ml, 20 ml

Tiaprost trometamol

0.196 mg/ml Iliren, MSD 10 ml

Ovary -CL Progesterone 1.38 g Progesterone

implant CIDR, Pzer Pack of 10

3.3 mg Norgestomet ear

implant and 3 mg

Norgestomet + 2 mg

Oestradiol injection Crestar, MSD Pack of 5

Three 186 mg ( each) +

one 400 mg medicated

progesterone device Triu-B, Virback Pack of 10

Hydroxyprogesterone

250mg/ ml Prolutek, 3 ml

Hydroxyprogesterone

250mg/ ml Duraprogen 3 ml

Ovary- Follicle Estrogen Oestradiol valerate

10 mg/ ml Progynon depot,

German Remedies 1 ml Ampoule

Oestradiol valerate

10 mg/ ml Pregheat, virbac 5 ml

Diagnosis of the silent estrus or anovulatory condition is essential for instituting the

most suitable treatment for oestrus induction. The diagnosis of ovarian function is usually

based on observing the behavioral signs of oestrus by the animal owner, rectal palpation of

ovaries for the presence of CL by veterinarian, or progesterone estimation twice at 10 days

interval. Poor estrus expression in dairy cattle decreases the efciency of visual observation

while small ovaries with embedded CL reduce the efciency of rectal palpation. On the other

hand, progesterone estimation is costlier, a cumbersome laboratory procedure and require at

least two sampling. Therefore, transrectal ultrasonic scanning has emerged as a very useful

tool for providing accurate and immediate diagnosis about the cyclic status of the animal.

These observations can also be helpful in predicting the day of oestrus and ovulation.

For initiating oestrus induction and synchronization program, it should be the priority

of veterinarian that protocol must be simple with minimum use of hormone, minimum

handling of animal and minimum visits. For this individual animal must be examined for

cyclic status (cyclic animals having CL vs anovular dairy cattle ). The choice of treatment is

based on cyclic status of animal. Following methods are commonly used for this purpose:

• Estrus and ovulation synchronization using prostaglandin F2α alone in cyclic animals

• Estrus and ovulation synchronization using progestogen

• Estrus and ovulation synchronization using GnRH based protocols

• Estrus and ovulation synchronization using progestogens and GnRH based protocol

For induction of estrus in cyclic animals having a functional CL – either the CL is regressed prematurely (with prostaglandins), or the luteal phase is extended articially with exogenous hormonal (progestogens) supplementation, so that it can then be terminated abruptly in order to mimic spontaneous regression of the CL. Prostaglandins are effective in inducing estrus in cyclic animals only. However, if given at random stage of estrous cycle oestrus induction rate are nearly 66% as this PG is effective only during two third period of estrous cycle. Acyclic buffaloes essentially require progesterone priming in order to induce overt, ovulatory and fertile estrus. PG administration is ineffective in anovular dairy cattle and also not required while administering progesterone implant.

Estrus and ovulation synchronization using prostaglandin F2 alone in cyclic animals —-

PGF2α causes luteolysis of CL and there is sharp decrease in concentration of progesterone hormone. After PG treatment animals are reported in heat between 2-5 days. PGF is not effective in animals that do not have a CL. Therefore, prepubertal heifers, postpartum acyclic females and even cyclic animals between rst ve to six days of the estrous cycle do not exhibit any response to PG administration. PGF alone is a very effective management tool in cyclic animals having a sound heat-detection program in the herd. There are three methods for estrus synchronization using PG injection.

First method : All animals having a detectable CL are given an injection of PG and observed for estrus for ve days. Animals found in heat are identied and inseminated. Conception rates are near spontaneous estrus .

PG —- AI at detected estrus

0d—– 2d————— 5d

Second method: In this method PGF2α is injected to all and animals are inseminated at

observed estrus between day 2-5. Animals not inseminated during this period are given

second injection of PG 11days later and insemination is done again at observed estrus.

PG —- Detect estrus& AI—– PG If no AI

AI at detected estrus

0d— 2d——– 5d———– 11 d

Third method: Inject the PGF2α in all the animals at day 0 (Day of treatment) and again at

day 11. Animals found in heat after 2

nd

PGF2α injections are inseminated at observed estrus.

1st PG——– 2nd PG AI at detected estrus

0d————– 11-14d

Estrus and ovulation synchronization using using progestogen —

CIDR intravaginal Pessary: —–

The CIDR is a “T” shaped device with exible wings that

collapse to form a rod that can be inserted into the vagina with an applicator. On the end

opposite to the wings of the insert a tail is attached to facilitate removal with ease. The

backbone of the CIDR is a nylon spine covered by progesterone (1.38g) impregnated

silicone skin. Progesterone concentrations are maintained at a relatively constant level

during the seven days the insert is in the vagina. It is always good to squeeze the vagina after

CIDR removal by back racking to clear the vagina for any pus type discharge at heat. An

injection of PG is also administered preferably 24 h before implant removal or at the time of

implant removal. Animals are found in heat within 48-72h of CIDR removal. [Lamb and

Larson, 2004].

CIDR—– PG — CIDR — AI

In Out

0—- 8—- 9— 11

Crestar ear implant : —–

The implant has two part-Crestar ear implant (3.3 mg Norgestomet) and Crestar injection (Crestar injection of 2 ml, containing 3 mg Norgestomet and 5 mg Estradiol valerate). The implant is placed for 7-9 days subcutaneously in ear along with Crestar injection. An injection of PG is also administered preferably 24 h before implant removal or at the time of implant removal. Animals are found in heat within 48-72h of CIDR removal (Nayak et al. 2009; Kumar and Mandape, 2004) There is no need to inject the Crestar injection and PG if animal is acyclic.

Double Ovsynch: —-

GnRH PG GnRH GnRH PG GnRH AI

16h

0 7 10 17 24 26 27

inseminations, without the need for estrus detection. This protocol is based on the

concept that rst injection of GnRH (day 0 of treatment) given at random stage of the

cycle causes ovulation of the largest dominant follicle and starts a new wave of follicular

development. Subsequently an injection of PG is given 7 days later to cause the lysis of

the CL. Later on, a second GnRH injection is given on day 9 to facilitate ovulation and

animal is inseminated around 16 h after the second GnRH. This xed time AI (FTAI)

protocol was named as Ovsynch and several variations have been developed

subsequently in the quest for higher conception rate, better ovulation synchronization

and scheduling resynchronization program.

Choice of treatment —-

It is very difcult to choose the protocol among different available protocol. It

should be kept in mind that these protocols are not a replacement of poor heat detection

system but help in reducing days open in those animals which are not detected in estrus at

proper time. In GnRH based protocols, estrus and ovulation synchronization is good

however, conception rate is not so high. It should be the priority of veterinarian that protocol

must be simple with minimum use of hormone, minimum handling of animal and minimum

visits.

Therefore, if animal is cyclic and having a mature CL, inject PG and inseminate the

animal on observed estrus. If animal is not observed for heat within 2-5 days, inject one more

injection of PG 11-14 days later after rst injection and bred at observed estrus. If animal is

acyclic use progesterone implant (CIDR/ Crestar) for 7-9 days and inject 400 IU PMSG one

day prior to implant removal. Animals are in heat between 36-48 h after implant removal and

should be inseminated. Using progesterone implant, acyclic buffalo should be inseminated

36 and 48 h whereas cyclic buffalo should be inseminated at 48 and 72h after implant

removal. There is no need to inject PG in conrmed acyclic animals. However, if animal

cyclicity is not conrmed then PG injection should be given 24 hr prior to implant removal. If

these implants are not available then Ovsynch Plus protocol is better choice in cyclic as well

as acyclic animals.

Progesterone Implant for confirmed acyclic cattle & buffaloes

Crestar PMSG Crestar

In 400 IU Out AI AI

36 h 12h

0 7 8 9 10

reference-on request