Product Description

Type C free-choice medicated feed for Beef & Dairy Cattle

SAFE-GUARD® (fenbendazole) Medicated Dewormer for Beef Cattle (20% Protein Block) is indicated for the removal and control of lungworms, stomach worms, and intestinal worms.


For The Treatment And Control Of:


  • Adult Dictyocaulus viviparus

Stomach worms

  • Adult brown stomach worms (Ostertagia ostertagi)
  • Adult and fourth stage larvae barberpole worms (Haemonchus contortus)
  • Fourth stage larvae barberpole worms (H. placei)
  • Adult and fourth stage larvae small stomach worms (Trichostrongylus axei)

Intestinal worms (Adult and fourth stage larvae):

  • Hookworms (Bunostomum phlebotomum)
  • Thread-necked intestinal worms (Nematodirus helvetianus)
  • Small intestinal worms (Cooperia punctata & C. oncophora)
  • Bankrupt worms (Trichostrongylus colubriformis)
  • Nodular worms (Oesophagostomum radiatum)


One block treats 8,000 lb. (500 lb. of cattle per 1.5 lb.).

Adequate forage must be available at all times to cattle receiving supplemental block feeding.

Safe-Guard® (fenbendazole) 20% Protein Deworming Block (Medicated) is designed for deworming pastured cattle by feeding these medicated blocks for three (3) days only as the sole source of salt. It is essential to establish full cattle adaptation to supplemental block feeding prior to treating cattle with Safe-Guard® 20% Protein Deworming Block (Medicated). Cattle behavior and per capita consumption must be established by feeding nonmedicated 20% Protein Blocks prior to medicated block treatment. Adaptation to block feed intake for medicated treatment may take twelve (12) to nineteen (19) days of prior exposure to unmedicated feed blocks depending on consumption rates and environmental conditions. When cattle block consumption of 0.1 pound (1.6 ounces) per 100 pounds of body weight (or 1.0 pound for a 1000-pound cow) per day is attained for several days on the nonmedicated 20% Protein Block, the three (3) day medicated treatment with Safe-Guard® 20% Protein Deworming Blocks (Medicated) may begin.

For effective treatment, the cattle must consume an average 0.1 pound of Safe-Guard® 20% Protein Deworming Blocks (Medicated) per 100 pounds of body weight each day for the three (3) days of treatment. This is equivalent to an average of one (1) pound per head per day to a 1000-pound cow for the three days of treatment in order to provide a total dose of 2.27 mg fenbendazole per pound of body weight. To commence deworming treatment, replace the nonmedicated blocks with Safe-Guard® 20% Protein deworming Blocks (Medicated). Place these medicated blocks at the same locations where cattle have demonstrated adequate per capita block intake (0.1 pound per 100 pounds of body weight per day).

DAILY TREATMENT (To be continued for three [3] days):

Cattle Body Weight
Average Block Intake
Number of Head
Per Block*


Following the three (3) day treatment any remaining Safe-Guard® 20% Protein Deworming Blocks (Medicated) should be removed from the pasture and cattle may be returned to their normal supplemental feeding program. Remaining blocks, or portions of blocks, can be utilized for retreatment purposes if used prior to the expiration date shown below.

It is essential that good block feeding husbandry practices be followed at all times. Block feeding techniques include, but are not limited to, a variety of practices. Blocks should be first located in those areas where cattle are seen to browse or loaf. It may be desirable to relocate unconsumed blocks to locations where obvious block consumption is identified. Increased consumption may often be obtained by moving feeding stations into shaded or loafing areas, closer to water source, increasing the number of blocks available to the animals or combinations of these practices. Decreased consumption may often be obtained by the reverse of the above practices.

Drug Feeding Rate

1.67 mg fenbendazole per kg body weight per day for three (3) days. Total dose for the three (3) day period of 5 mg fenbendazole per kg of body weight (2.27 mg fenbendazole per pound).

Do not underdose. Ensure each animal receives a complete dose based on a current body weight. Underdosing may result in ineffective treatment, and encourage the development of parasite resistance.


25 LBS (11.34 kg)

Active Ingredient

Fenbendazole 750 mg/lb


Store at or below 25 °C (77 °F).


The Safety Data Sheet (SDS) contains more detailed occupational safety information. For customer service, adverse effects reporting, and/or a copy of the SDS, call 1-800-211-3573. For additional information about adverse drug experience reporting for animal drugs, contact FDA at 1-888-FDAVETS, or

Other Warnings

Parasite resistance may develop to any dewormer, and has been reported for most classes of dewormers. Treatment with a dewormer used in conjunction with parasite management practices appropriate to the geographic area and the animal(s) to be treated may slow the development of parasite resistance. Fecal examinations or other diagnostic tests and parasite management history should be used to determine if the product is appropriate for the herd, prior to the use of any dewormer. Following the use of any dewormer, effectiveness of treatment should be monitored (for example, with the use of a fecal egg count reduction test or another appropriate method). A decrease in a drug’s effectiveness over time as calculated by fecal egg count reduction tests may indicate the development of resistance to the dewormer administered. Your parasite management plan should be adjusted accordingly based on regular monitoring.


Important Safety Information

Do not use in beef calves less than 2 months old, dairy calves and veal calves. A withdrawal period has not been established for this product in pre-ruminating calves. Additionally, the following meat withdrawal and milk discard times apply:
Safe-Guard 20% Protein Type C Medicated Block: Cattle must not be slaughtered for 16 days. For use in beef cattle only.


U.S. only: Merck Animal Health
The Safety Data Sheet (SDS) contains more detailed occupational safety information.
For customer service or to request a copy of the SDS, please call 1-800-521-5767 or email
For product questions or to report an adverse event, call 1-800-211-3573 or email
For additional information about adverse drug experience reporting for animal drugs, contact FDA at 1-888-FDAVETS,
For more information regarding efficacy and safety data, go to
For additional information, please see the product label.

Unsure when to deworm your herd?

Questioning how much you will need? Use the treatment schedule and dosage calculator to create your customized cattle deworming plan.

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