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Synovex One Grass

This page contains information on Synovex One Grass for veterinary use.
The information provided typically includes the following:
  • Synovex One Grass Indications
  • Warnings and cautions for Synovex One Grass
  • Direction and dosage information for Synovex One Grass

Synovex One Grass

This treatment applies to the following species:
Company: Zoetis

(trenbolone acetate and estradiol benzoate extended-release implants)

150 mg trenbolone acetate and 21 mg estradiol benzoate per implant


SYNOVEX ONE Grass (trenbolone acetate and estradiol benzoate extended-release implants) is a growth promoting implant containing 150 mg of trenbolone acetate and 21 mg of estradiol benzoate with a porous polymer film coating that extends the pay-out period of the final formulation up to 200 days. Each implant consists of six pellets. Ten implants are provided in each cartridge.

DOSAGE: One implant (six pellets), containing 150 mg of trenbolone acetate and 21 mg of estradiol benzoate, is administered to each steer or heifer by subcutaneous implantation in the middle one-third of the ear.

The ten-dose cartridge of SYNOVEX ONE Grass is designed to be used exclusively with a Synovex applicator.

ANIMAL SAFETY WARNING: Bulling, vaginal and rectal prolapse, udder development, ventral edema and elevated tailheads have occasionally been reported in heifers administered SYNOVEX ONE Grass implants.

Directions For Use

Implant complete contents of one cartridge cell per steer or heifer. Approved implantation technique is fully described in the fold-out carton section.

NOTE: Never sacrifice careful, clean technique for speed of implantation.

How To Implant

For Use With The Synovex Applicator

Study the following instructions carefully, then proceed step by step, until the technique becomes routine. Many head can be implanted per hour by an experienced team, one member of which should be assigned to do nothing but the implantation. Care should be taken to insure the hands of the person administering the implant are clean and only sanitary instruments are used.

Synovex One Grass Indications For Use

For increased rate of weight gain for up to 200 days in steers and heifers fed in confinement for slaughter.

Do not use in veal calves. Effectiveness and animal safety in veal calves have not been established.

Not for use in dairy or beef replacement heifers.


Store unopened product at controlled room temperature 20°-25°C (68°-77°F) with excursions between 15°-30°C (59°-86°F). Avoid excessive heat and humidity. Use product before the expiration date printed on the label.

Once the pouch is opened, unused product may be stored in the end-folded pouch (away from light) for up to six months under refrigerated conditions 2°-8°C (36°-47°F) or at room temperature 20°-25°C (68°-77°F) with excursions between 15°-30°C (59°- 86°F) for up to one month.


SYNOVEX ONE Grass waste materials should be disposed of according to prescribed Federal, State, and Local guidelines.



Withdrawal Period

No withdrawal period is required when used according to labeling.

A withdrawal period has not been established for this product in pre-ruminating calves. Do not use in calves to be processed for veal.

Implant pellets in ear only. Any other location is a violation of Federal law. Do not attempt salvage of implanted site for human or animal food.

Keep this and all drugs out of the reach of children.

Restricted Drug (California)-Use Only as Directed.

Step 1 Loading The Applicator

Load the applicator following the directions outlined in the instruction manual accompanying each applicator. When using metal revolver style applicator, use orange adapter kit.

Additional information for the individual applicator user guides can be found at:

Step 2 Restraint

The animal must be confined in a restraint mechanism (squeeze chute or head gate). The implant site on the back of the ear should be prepared by scrubbing with a firm bristled brush that has been soaked in a germicidal solution.

Note: If implanting horned cattle, greater safety is provided when the head is controlled by the use of a bull lead (nose tongs).

Step 3 Implant Site

Divide the ear into three imaginary sections as illustrated. The implanted pellets should be deposited in the center one-third of the ear as shown. To accomplish this, the applicator needle should be inserted in the outer one-third of the ear as indicated by the “X” in the illustration. Implanting too close to the head may cause abnormal sexual behavior. Care should be taken to avoid severing the major arteries of the ear.

Step 4 Insert Needle

Grasp the ear with one hand. Holding the applicator firmly with the other hand, penetrate the skin at the point shown by the “X”. Thrust the needle under the skin taking care not to penetrate the cartilage. Ease the applicator forward (toward the base of the ear) until the full needle length is beneath the skin.

Step 5 Pellet Implantation

When the needle is completely inserted, activate the instrument by squeezing the trigger completely. Refer to instructions for individual applicator.

Step 6 Inspection

Check the implant site. If properly administered, the implants should lie in a straight line under the skin. Re-cock the applicator. Disinfect the applicator needle in a germicidal solution. The applicator is now ready to implant the next animal.


Read ALL sides of carton

Approved by FDA under NADA # 141-348

NET CONTENTS: One pouch contains ten 10-dose cartridges (100 implants).


Each Cartridge Contains 10 implants (100 implants total)

Manufactured By A Non-Sterilizing Process

Distributed by: Zoetis Inc., Kalamazoo, MI 49007


CPN: 3690398.1

Telephone:   269-359-4414
Customer Service:   888-963-8471
THIS SERVICE AND DATA ARE PROVIDED "AS IS". DVMetrics assumes no liability, and each user assumes full risk, responsibility, and liability, related to its use of the DVMetrics service and data. See the Terms of Use for further details.

Copyright © 2023 Animalytix LLC. Updated: 2023-05-30