No abstract

Multi-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

No abstract

The Edwards Plateau region of Texas is largely used for grazing cattle and small ruminants. Tick parasitism in range livestock can occur year-round with direct production losses manifested as body weight or condition. The objective was to assess two acaricide treatments on the active tick burden on livestock within two forage growing seasons (winter through summer). At the Sonora AgriLife Station, 22 Bos taurus crossbred heifers (248 ± 47 kg) were maintained on 97 hectares of rangeland. Tick burden was assessed by individual animal inspection every two wk from 18-Dec-2019 to 11-May-2020 (Season 1) and from 8-Jun-2020 to 3-Aug-2020 (Season 2). Acaricide treatment was applied each date to heifers chosen randomly to serve in the non-treated control (control: 11 heifers) or acaricide-treated (treatment: 11 heifers) groups. Season 1 acaricide treatment was a pour-on synthetic pyrethroid (11 dates) and Season 2 was a diluted synthetic pyrethroid whole-body spray (5 dates). Tick species observed included Amblyomma americanum and Dermacentor albipictus. Tick burden (total counts) and body condition score differences were determined by analysis of variance procedures. For tick burden, there were significant differences (P < 0.0012) between treatment (0.528 ± 0.06) and control (0.819 ± 0.06) heifers in Season 1 (0.673 ± 10.44), and no differences (P > 0.11) between treatment (0.642 ± 0.07) and control (0.799 ± 0.07) heifers in Season 2 (0.721 ± 2.64). For body condition score, there were no differences (P > 0.72) between treatment (5.61 ± 0.04) and control (5.59 ± 0.04) heifers in Season 1 nor Season 2 (5.51 ± 0.005 and 5.80 ± 0.47, respectively). Season 1 acaricide treatment was effective in controlling tick burden (efficacy = 3–4 wk) as compared to Season 2 (efficacy = 1–2 wk). Tick burdens observed under the conditions of this study had no effect on body condition.