Effects of Pyrethroid and Pyrethrin Insecticides on Beef Bull Reproductive Parameters

Abstract Text: The objective of this research was to determine the effects of pyrethroid, beta-cyfluthrin, and pyrethrin premise and fog sprays used in combination with pyrethroid, cyfluthrin and beta-cyfluthrin, pour-ons and fly tags on bull reproductive parameters. Concern has risen in the beef industry that pyrethroids and pyrethrins, common insecticides, may impact bull fertility. Studies with rodents indicated insecticides were associated with sperm abnormalities and disruption of hormones. Recent experiments with beef bulls demonstrated no effects on sperm motility or morphology when Cylence pour-on and Cylence Ultra fly tags were applied at labeled doses. Angus × Simmental crossbred bulls (n = 23; average initial BW = 796 ± 160 kg) were blocked by source and randomly assigned to 2 treatments: (1) pour-on and fly tags (CONT), or (2) pour-on, fly tags, premise spray and fog spray (EXP).  The CONT group was treated with Cylence pour-on (active ingredient cyfluthrin; 1%) and 2 Cylence Ultra fly tags (active ingredients beta-cyfluthrin; 8% and piperonyl butoxide; 20%).  The EXP group was treated with Cylence pour-on, 2 Cylence Ultra fly tags, Tempo premise spray (active ingredients beta-cyfluthrin, cyano and methyl 3; 11.8%) and LD-44Z fog spray (pyrethrins; 0.5% and piperonyl butoxide; 4%). Scrotal circumferences were measured initially and at the end of the 10 wk experimental period. Semen was collected weekly via electroejaculation.  Whole blood, as a source of serum, was collected from the tail vein weekly to determine peripheral blood testosterone concentrations.  Semen was analyzed for progressive and overall motility using computer-assisted semen analysis. There were no differences (P ≥ 0.22) in initial or final scrotal circumferences. There was a treatment × wk interaction (P < 0.01) for overall motility, progressive motility, and serum testosterone concentration. At wk 2, CONT bulls had greater (P = 0.05) overall sperm motility and tended to have greater (P = 0.07) progressive motility than EXP bulls; however, at wk 7, EXP bulls tended to have greater (P = 0.09) progressive motility than CONT bulls. At wk 3, EXP bulls tended to have greater (P = 0.10) testosterone concentration than CONT bulls; however, at wk 1 and 9, CONT bulls had greater (P ≤ 0.05) concentrations of testosterone than EXP bulls. Using pyrethrin and pyrethroid premise and fog sprays in combination with fly-tags and pour-ons had variable effects over a 10 wk period on sperm motility and testosterone concentrations. 

Keywords: bull, pyrethroid, reproduction