Fecal Egg Counts and Performance of Stocker Calves Treated with Various Anthelmintics

Treatment against gastrointestinal parasites have been reported to increase cattle growth; however, effects of long-acting eprinomectin (LAE) on stocker growth and performance has not been widely evaluated. Therefore, objectives of this study were to determine differences in fecal egg counts (FEC) and performance of stockers receiving dual oxfendazole/moxidectin treatment (Co-Trt) and LAE. Newly received Angus based crossbred steers (n=59; BW = 284.26 ± 5.79 kg) were stratified by FEC, BW, and BCS and randomly allocated to treatments: Control (CON; n=14), long-acting eprinomectin (LAE; n=15), oxfendazole and moxidectin on d 0 (COMBO; n=15), and oxfendazole d 0 plus moxidectin d 45 (O+M; n=15). Steers were commingled and allowed to graze bermudagrass paddocks using a management intensive grazing system (42,243.46 kg/ha). Fecal samples were collected and BW, BCS, and hair coat scores (HCS) determined on d 0, 15, 31, 63, and 92. Fly counts were collected on d 0, 16, 32, 44, 64, and 93. Statistical analysis was performed using the MIXED procedure of SAS and three orthogonal contrasts were used: 1) CON vs treated steers, 2) LAE vs Co-Trt, and 3) COMBO vs O+M. A treatment*day interaction (P < 0.01) was observed for FEC with COMBO having the lowest FEC on d 15 but the greatest FEC on d 63 compared with all other treatment and d combinations. Body weight on d 0, 15, 31, and 63 did not differ (P≤0.24); however, BW tended (P=0.09) to be greater for LAE steers compared with Co-Trt steers on d 93. Steer BCS did not differ (P≤0.22) across treatments on d 15, 31, and 63, but was greater (P