The effect of cyfluthrin, a commercially available synthetic pyrethroid, on bovine semen quality and pregnancy rates

Abstract

Reports of research in laboratory animals and clinical case studies in livestock suggest pyrethroids may reduce fertility. The objective of the experiments reported here was to assess the effects of cyfluthrin on cattle reproduction. In experiment 1 Angus x Simmental bulls were allocated to the following treatments: control with no pesticide applied (n=5), cyfluthrin pour-on (n=5), cyfluthrin fly tag (n=7), and cyfluthrin pour-on plus fly tag (n=7). Semen was collected weekly for nine weeks and analyzed for overall sperm motility, progressive sperm motility, and sperm morphology with the aid of computer-assisted semen analysis. Blood samples were taken weekly at the time of semen collection and properly stored until testosterone concentrations could be assayed. There were no differences in overall motility (p=0.41), progressive motility (p=0.60) or morphology (p=0.41) among treatments. Mean testosterone concentrations did not differ (p=0.16) between control and treated bulls. In experiment 2 Angus and crossbred cows were synchronized for an artificial insemination (AI) program and randomly assigned to a control (n=61) or treated group (n=62). The treated group received both pour-on and fly tags at label doses. Insecticide was applied to the treated group at the time of controlled internal drug release (CIDR) insertion. Blood samples for progesterone analysis were collected on days 10 and 17 following timed AI. Pregnancy status was assessed 35 days after AI. The treated group had lower (p=0.02) progesterone concentrations on day 10 but not on day 17 (p=0.57). No differences (p=0.65) were observed in pregnancy rates between treatments. Reproductive parameters measured in bulls were not affected by cyfluthrin pour-ons or fly tags, even when used in combination. Transient effects were observed in the concentration of progesterone in the plasma of cows, but did not result in differences in pregnancy rates observed at 35 days of gestation.