Effect of Safe-guard® Free-choice Protein Blocks on Trichostrongyle Nematodes in Pastured Cattle from Eastern South Dakota

Parasitic nematodes have significant detrimental effects on the profitability of beef production in South Dakota. Administering anthelmintics can be inconvenient and expensive when treating cattle on pasture. Free-choice anthelmintics were developed to improve the ability of beef producers to effectively deworm cattle without passing them through a cattle chute. The convenience of free-choice anthelmintics outweighs those of traditional deworming practices; however, the efficacy of the free-choice anthelmintics has not been tested under pasture conditions in the United States Northern Great Plains. The purpose of this study was to determine the efficacy of Safe-Guard® (fenbendazole) Freechoice Protein Blocks in pastures from eastern South Dakota. Two adjacent cattle herds were used for this study. A group of 42 heifers (treatment) were given one free-choice SafeGuard® Protein block for four days. A similar group of 22 steers (controls) were given similar, but non-medicated protein blocks. Both groups were parasitized with trichostrongyle nematodes; PCR results indicated the presence of Haemonchus spp., Cooperia spp., Ostertagia spp. and Trichostrongylus spp. in the heifer herd. Prior to treatment, the arithmetic mean trichostrongyle egg output was numerically higher in the untreated steers (35.82 eggs/gram) than the treated heifers (22.63 eggs/gram), but not statistically different. After treatment with the Safe-Guard® blocks, egg output dropped significantly to 1.50 eggs/gram (greater than 93% reduction) in the treatment group, but increased significantly in the untreated group to an average of 69.03 eggs/gram (greater than 92% increase). Based upon the calculated consumption rate of the SafeGuard® Protein Block by the treatment group, the average dosage consumed was lower than that recommended by the manufacturer. In spite of the lower intake, access to the medicated blocks significantly decreased trichostrongyle nematode loads in the treated cattle during the study period.