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A. C. Lewis, E. A. Watson, A. L. Sonntag, K. E. Kasten, B. Papajeski, J. C. Robertson, E. A. Backes, C. A. Porr, A. J. Davis, 035 Effects of Moxidectin/Oxfendazole and Long-Acting Eprinomectin Treatment on Fecal Egg Counts and Performance in Newly Received Stocker Calves, Journal of Animal Science, Volume 95, Issue suppl_1, December 2016, Page 17, https://doi.org/10.2527/ssasas2017.035
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Abstract
The objectives of this study were to evaluate effects of various anthelmintic treatments on fecal egg counts (FEC) and performance of newly received stocker calves. Upon arrival to the Murray State University Beef Unit, steers (n = 66) were allowed a 7 d adjustment period prior to allocation of treatment. Steers were randomly allocated to treatment based on BW (296.41 ± 23.67 kg) and FEC (13.67 eggs/gram; EPG). Treatments included: control (n = 10; no anthelmintic administration; CON); moxidectin/oxfendazole combination (n = 28; COMBO); and long-acting eprinomectin (n = 28; LAE). Steers were comingled and grazed mixed grass pastures with rotation based on forage availability. Paddock size ranged from 0.40 to 0.81-ha with an average stocking density of 47,255.4 kg/ha. Fecal samples, BW, BCS, and hair coat scores (HCS) were collected on d 0, 13, 27, 56, 90, and 101. Fly counts were performed from an all-terrain vehicle while steers grazed on d 14, 31, 61, 91, and 100. Statistical analysis was performed using the MIXED procedure of SAS (experimental unit = steer, repeated measure = day). Two preplanned orthogonal contrasts were used to evaluate effects and included comparisons of: 1) CON vs treated steers; and 2) COMBO vs LAE steers. Controls differed from treated steers for EPG (P = 0.05) and LAE steers differed from COMBO steers (P < 0.01). A treatment × d interaction (P < 0.01) was detected for EPG. The highest EPG were observed in the COMBO steers on d 101, 90, 56 (62.57, 47.34, and 44.73 EPG, respectively) with the fewest EPG observed on d 13 (COMBO = 1.56, LAE = 2.02 EPG). Body weight and ADG were similar between treatments throughout the study (P > 0.09) except for ADG from d 13 to 27, in which CON steers exhibited a higher ADG (P = 0.04) compared to treated steers (1.03 vs 0.24). Greater (P = 0.06) BCS were observed for CON versus treated steers on d 27 (5.5 vs 5, respectively); however, BCS were similar (P > 0.1) throughout the rest of the study. Fly counts were not affected (P = 0.78) by treatment, but were affected (P < 0.01) by d with the highest fly counts occurring on d 100 and the fewest flies on d 31 (19.49 and 6.14, respectively). Data suggest anthelmintic use may reduce FEC without improving performance in stocker calves under management intensive grazing systems.
