PS-4 Evaluating the Effects of Artificial Rainfall and Permethrin Resistance Status on the Efficacy of Common Pour-On Formulation Delivered to Beef Heifers in a Controlled Environment. (22nd October 2022)

• Record Type: Journal Article
• Authors: Castro, Dalila; Sanchez-Sandoval, Ulises A; Ramirez, Jovannah; Smythe, Brandon G
• Is Part Of: Journal of animal science. Volume 100(2022)Supplement 4
• Page Start: 18
• Page End: 18
• Publication Date: 2022-10-22
• Subjects: horn flies -- permethrin -- rainfall; Livestock -- Periodicals; Livestock; Electronic journals; Periodicals; 636.005
• DOI: 10.1093/jas/skac313.025
• Languages: English
• ISSNs: 0021-8812

Abstract

Abstract: The objective of this study is to determine the impact of rainfall on the duration of efficacy of a commercial pour-on against susceptible (SS) and permethrin resistant (PR) horn flies. Eighteen Angus-Hereford crossbred heifers (BW) were used in a completely randomized design with repeated measures to determine the efficacy and longevity of a permethrin-based pour-on. Animals were randomly assigned to one of two fly infestations (SS or PR) and within infestation to one of three rainfall regimens [no rain (NR), no rain with a pour-on (NP) treatment, and rain with a pour-on (RP) treatment]. All heifers were housed in outdoor roofed pens within the corresponding treatment group and animals with NP and RP groups were treated once on day 0 at the label rate. Once a week for four weeks all animals were placed into individual indoor screened rooms where the fly infestations were administered. Live fly counts were acquired 24 h following each infestation. Animal with RP received approximately 2.54 cm of artificially provided rainfall within 2 hours following each weakly horn fly count. A treatment × day x fly interaction (P < 0.01) was observed. In general, NR groups maintained higher (P < 0.05) populations of SS and PR for 22 and 8 days post-treatment, respectively. Regardless, of fly species, rainfall had no (P > 0.05) influence on product efficacy. In conclusion, insecticide resistance status appears to be more influential than heavy rainfall in the longevity of permethrin-based pour-on products.