Safe-Guard (fenbendazole) En-Pro-Al Molasses Deworming Supplement Block (Medicated) is designed for deworming pastured cattle by feeding these medicated blocks for three days only as the sole source of salt.


Medicated Dewormer for Beef Cattle




For the removal and control of: Lungworm; Stomach worms: Barberpole worms, Brown stomach worms, Small stomach worms; Intestinal worms: Hookworms, Thread-necked intestinal worms, Small intestinal worms; Bankrupt worms; Nodular worms


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

It is essential to establish full cattle adaptation to supplemental block feeding prior to treating cattle with Safe-Guard En-Pro-AL Molasses Deworming Block (Medicated). Cattle behavior and per capita consumption must be established by feeding non-medicated En-Pro-AL Blocks prior to medicated block treatment. Adaption to block feed intake for medicated treatment may take 12 to 19 days prior exposure to unmedicated feed blocks depending on consumption rates and environmental conditions. When cattle block consumption of 0.1 pound (1.6 oz) per 100 pounds of body weight (or 1.0 lb for mature cattle) per day is attained for several days on the nonmedicated En-Pro-AL Block, the three (3) day medicated treatment with Safe-Guard En-Pro-AL Molasses Deworming Supplement Blocks (Medicated) may begin.


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


Residue Warning

Cattle must not be slaughtered within 11 days following last treatment. Under conditions of continued exposure to parasites, retreatment may be needed after six to eight weeks.

EN-PRO-AL is a registered trademark of SWEETLIX.


Code: 069291
25 lb Block

For more information about Merck Animal Health Products, call 1-800-441-8272.

RESIDUE WARNING: Cattle must not be slaughtered within 11 days following last treatment. For dairy cattle, the milk discard time is zero hours. A withdrawal period has not been established for this product in pre-ruminating calves. Do not use in calves to be processed for veal.

For additional information, please see the product label.

Technical Information

SAFE-GUARD® – Brown Stomach Worm – Does It Arrest In U.S. Dairy Cattle?

Producers, veterinarians and others involved in the dairy industry often assume that parasite data generated in beef cattle is fully applicable to dairy cattle. Such assumptions can be costly to dairy producers who seek cost-effective solutions to the problem of worm control. A good example of this difference can be found in research conducted at the University of Kentucky dairy farm. In this two-year study1,2,3, 50 parasite-naïve tester dairy calves were allowed to graze pastures for one month. Worms picked up during grazing were then recovered from the calves and identified. This method allows for determination of the type and size of the worm population present on contaminated pasture. In this study, Nematodirus was the most common worm found with an average of 2,220 worms per calf. Cooperia was the second most common worm found (2,018 worms). Brown stomach worm was third (846 worms ). No population of arrested brown stomach worm was found. These results were surprising because the study had been conducted to determine the seasonal pattern of arrested development for brown stomach worm.

SAFE-GUARD® – Deworming Lactating Dairy Cows During The Transition Period

Deworming lactating dairy cows is a venture beyond treating disease. Although most dairy cows have sufficient immunity such that parasitic disease will not occur, they’re not immune from production losses caused by parasite exposure and the subsequent development of infection. Internal parasites interfere with efficient production and, therefore, the strategic deworming of lactating dairy cows is designed to prevent production losses caused by these parasites. Whole-herd deworming in late fall or early winter is a good strategy to maintain a parasite-free herd throughout the winter months in northern climates; however, a separate strategy for spring and summer to control internal parasites is required. During this period, individual animal treatment provides the very best control if production losses are to be prevented. Management may find, when feeding transitional groups in freestalls, deworming the cows via the feed (TMR) is cost-effective and laborsaving.

SAFE-GUARD® – Technical Bulletin

SAFE-GUARD® (FENBENDAZOLE) – Guide To Internal Parasites Of Ruminants

Health Impact and Characteristics of Internal Parasites

SAFE-GUARD® (FENBENDAZOLE) – Quantity Recommendation Chart

Chart containing pounds of Safe-Guard 1.96% and Safe-Guard .5% per number of calves and average calf weight.


Three dewormer block consumption studies were conducted using a total of 143 mature cattle (approximately 50 at each location). Locations of the studies were Alabama, Louisiana and Wyoming. An adaptation period of four to 19 days with unmedicated feedblocks was required prior to offering the medicated dewormer blocks. The adaptation period varied depending upon current and previous herd feeding and management practices in addition to weather conditions. The medicated dewormer blocks were given for a three-day treatment period with the total Safe-Guard Block consumption for the three-day period calculated to be 5mg fenbendazole per kg body weight (2.27mg/lb. body weight). All cattle were grazing on pasture. No supplemental feed was given except for the dewormer blocks. The total number of dewormer blocks placed in each pasture was determined at the beginning of each study and was based on the number of cattle in each pasture and other conditions such as physical layout of the pasture and watering areas. Fecal samples were collected from all cattle before treatment and again approximately 14 days after treatment. Fecal egg counts were determined for all samples.


A study was conducted to evaluate the efficacy of Safe-Guard medicated dewormer blocks against natural infections of gastrointestinal nematodes of cattle. Twenty calves were divided into two groups of 10 each. One group served as non-medicated controls while the other group served as the treatment group. Mixed breed calves (Hereford, Angus and Brahman) were purchased from the same farm with an average weight of approximately 500 pounds. They had been on pastures naturally contaminated with nematode larvae for several months prior to shipment to the study location. Upon arrival, calves were placed in a drylot and acclimated for seven days prior to initiation of the study. During this period, they were allowed access to unmedicated dewormer blocks similar to those to be used in the study. Each calf was then placed in an individual pen so that block consumption could be monitored. They each received dewormer blocks without fenbendazole for one week prior to being offered medicated blocks. Untreated controls were not offered blocks. All calves received hay and water but no other supplemental feed or source of salt during the preliminary phase. Fecal samples were taken prior to treatment with Safe-Guard medicated dewormer blocks and again five days after the last day of treatment. All calves were necropsied five days after the last day of treatment to determine actual nematode count and species present.

SAFE-GUARD® BLOCK RESEARCH – Southeastern U.S.A. Study

Fall and winter are key times to be promoting the En-pro-al/Safe-Guard (fenbendazole) deworming block for use in the Southern U.S. The following Safe-Guard treatment program in weaning cattle grazing coastal Bermuda pastures also achieved seasonal control. As a result, calves gained an additional 67 lbs. per head compared to calves given a traditional single treatment in November.


  1. Nationwide Cattle Survey: Zeroing in on Parasites. Large Animal Veterinarian, September, 1993, pp. 30-32.
  2. Transmission of Gastrointestinal Parasites in Dairy Calves on Pasture in Central Kentucky from 1987 through 1989. Journal of The Helminthological Society of Washington, 58(2), 1991, pp.220-226.
  3. Control of Gastrointestinal Nematodes in Dairy Cattle Under Intensive Rotational Grazing Management. SARE Project # LNE95-055.