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Evaluation of the anthelmintic efficacy of a single subcutaneous injection of LongRange™ in stocker calves when compared to a positive (Dectomax™) and a negative (saline) control
Stocker cattle are commonly impacted by sub-clinical parasitism. Single dose anthelmintics have shown to reduce internal worm load for approximately 30 days. LongRange™ is the first single dose extended-release anthelminitic providing parasite control for a minimum of 100 days. Crossbred heifers (n = 288; 254.47 lbs ± 29.40) were completely randomized by initial weight across fifteen pastures. Pastures were randomly assigned to either: 1) LongRange™ administered at 1 mL/50kg; 2) Dectomax™ administered at 1 mL/50 kg with Cyonara Plus™ insecticide given at 10 mL/272.16kg; or 3) Saline administered at 1mL/45.4 kg, with five pastures per treatment. Weights were taken on individual heifers and fecal samples were taken from five randomly selected heifers per pasture. Weights and fecal samples were taken on d 0, 47, and 96. Heifers did not exhibit a level of fecal egg counts (FEC) that would negatively impact performance. The fly counts began on d 50 and continued on a weekly basis until end of trial. Three heifers were randomly selected per pasture and pictures were taken of each heifer using a DSLR camera with a telephoto zoom lens. Pictures of heifers were uploaded to a computer program where flies were highlighted and counted by hand. Weight gains were similar between treatments (P ≥ 0.27) throughout the 96 d study. On initial collection (P = 0.37) and mid collection (P = 0.34) FEC were similar among treatments. However, on final collection, Dectomax™ had lower (P = 0.05) FEC compared to the Saline and LongRange™ treatments. The highest FEC on trial heifers was 10.8 eggs per gram which is well below the economic threshold. LongRange™ treated heifers had lower (P = 0.04) fly counts than Dectomax™ and Saline treated heifers. Worm loads in heifers were not high enough to impact performance making it difficult to determine the efficacy of the anthelmintics.
Keywords: anthelmintic, fly count, stocker