A Fecal egg count reduction test evaluating macrocyclic lactones using cattle treated 118 days earlier with saline, albendazole in combination with doramectin, or an extended-release formulation of eprinomectin

Abstract

A fecal egg count reduction (FECR) test was conducted on stocker cattle treated 118 days earlier with saline injection (S); 0.09 mg/lb (200 mcg/kg) BW doramectin injection concomitantly with 4.54 mg/lb (10 mg/kg) BW albendazole oral suspension (DA); or 0.45 mg/lb (1 mg/kg) BW eprinomectin extended-release injection (ERE), and then continuously grazed by treatment group in groups of 4 until the start of the current study. In total, there were 8 S, 12 DA, and 12 ERE grazing groups (pastures of origin). Three animals from each pasture were randomly allocated for injection with ivermectin, doramectin or moxidectin, all at the rate of 0.09 mg/lb (200 mcg/kg) BW. Fecal samples were obtained at days -1 and 15, with treatments on day 0. Additionally, coprocultures were conducted on individual fecal samples collected on days -1 and 15.

On day -1 of the FECR test, the arithmetic mean strongyle eggs per gram of feces counts (EPG) across all pastures of origin were 412, 570, and 321 for the ivermectin, doramectin, and moxidectin-treated cattle, respectively. Day 15 egg counts in the same order were 177, 335, and 28. Using the above arithmetic means and by standard equation, the overall mean FECR percentages were 57.0, 41.2, and 91.2 for ivermectin, doramectin, and moxidectin, respectively. Lowest FECR test percentages were seen for animals from the ERE pastures. Coproculture larvae populations harvested on both days -1 and 15 were primarily Haemonchus placei and Cooperia punctata, regardless of animal's pasture of origin or FECR test treatment.