Tick burden observed on cattle and sheep during winter season on the Edwards Plateau of Texas.
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AbstractMulti-species livestock grazing is a common practice in the Edwards Plateau of Texas. Winter demands on livestock are high because of forage quality and quantity limitations and stresses of tick parasitism. Our objective was to assess winter-active tick burden on livestock and gauge effectiveness of a pour-on synthetic pyrethroid acaricide. At the Sonora AgriLife Station, 26 Bos taurus crossbred heifers (260 6 kg) and 28 Dorper ewes (42 1 kg) were maintained on 97.125 hectares of rangeland. Tick burden was assessed by individual animal inspection on: 12-18-2017, 01-05-2018, 01-122018, 01-26-2018, 02-09-2018, 02-16-2018, 02-23-2018, and 03-08-2018. Trial 1 acaricide treatment was applied 01-05-2018 on heifers and ewes chosen randomly to serve in the non-treated control (13 heifers; 14 ewes) or acaricide-treated (13 heifers; 14 ewes) groups. Trial 2 acaricide treatment was applied 02-16-2018 using a switchback design. Tick species included Amblyomma americanum, Dermacentor albipictus, and Ixodes scapularis. Tick burden differences were determined by analysis of variance procedures. There were no differences in tick burden on heifers or ewes prior to acaricide application for Trial 1 nor Trial 2 (P > 0.276, 0.002 0.46; P > 0.354, 0.002 0.11 and P > 0.606, 0.002 0.05; P > 0.705, 0.001 1.34, respectively). There were no differences (P > 0.149) between acaricide-treated (0.519 0.05) and non-treated control (0.644 0.07) heifers in Trial 1 nor Trial 2 (0.759 0.07 and 0.404 0.04, respectively). Similarly, there were no differences (P > 0.997) between acaricide-treated (2.964 0.31) and non-treated control (2.965 0.3) ewes in Trial 1 nor Trial 2 (1.015 0.13 and 5.563 0.45, respectively). We conclude ticks challenge the well-being and production in overwintering livestock in the Edwards Plateau. Alternative acaricides should be evaluated for efficacy and efficiency in these production systems
